Forms of allergic reactions. Types of allergic reactions. In order to confirm the diagnosis and identify a specific irritant, various tests and analyzes are performed.

Different types of allergies are observed in almost half of the people living in large cities. The prevalence of this disease among villagers is much less. But this is recorded data based on patients' requests to doctors.

According to medical forecasts, there are many more allergy sufferers in the world - it's just that some allergic reactions are weak, do not cause serious discomfort, so people do not seek medical help.

Clinical picture

WHAT DOCTORS SAY ABOUT EFFECTIVE ALLERGY TREATMENTS

Vice-President of the Association of Children's Allergists and Immunologists of Russia. Pediatrician, allergist-immunologist. Smolkin Yuri Solomonovich

Practical medical experience: more than 30 years

The first descriptions of such a disease are found in the writings of ancient healers of the 5th century BC. Back then, allergies were extremely rare.

In recent decades, the number of patients has been constantly growing. There are several reasons for this: weakened immunity, an increase in the number of toxic substances that are used everywhere, a desire for sterility and a minimal pathogenic load on the immune system.

As a result, he becomes too "suspicious" and sees the enemy in familiar and everyday substances - even those that do not pose a potential danger.

What is an allergy and why does it occur?

This is the individual sensitivity of the human body, more precisely, its immune system to a certain irritant substance. The immune system perceives this substance as a serious threat.

Normally, the immune system "monitors" bacteria, viruses and other pathogens that enter the body in order to neutralize or destroy them in time, preventing the disease.

Allergy is a “false alarm” of the immune system, which is based on an erroneous perception of an allergen substance. Faced with an irritant, he perceives a certain substance as a pathogen, and reacts with the release of histamine. Histamine itself provokes the appearance of signs characteristic of allergies. The nature of the symptoms themselves depends on the type of allergen, the place of its entry and the degree of individual sensitivity.

The cause of allergies is not at all increased vigilance of the immune system, but a malfunction in its work. This failure can be caused by a single factor or a combination of them:

1. Weakening of the immune system, which occurs in the presence of chronic diseases, helminthic invasions.
2. Heredity. If any allergy, even a mild one, is in one parent, this gives a 30% chance that this disease will manifest itself in the baby. If both parents have manifestations of this disease to one degree or another, the likelihood that a child will be born with an allergic person increases to almost 70%.
3. Genetic failure, as a result of which the immune system does not work correctly.
4. Violation of the composition of the intestinal microflora.
5. Formation of immunity in conditions of high purity. Without encountering pathogens, it "trains" on the surrounding substances.
6. Contact with a large amount of "chemistry", as a result of which the body perceives any new substance as a potential threat.

An allergen (a substance to which an atypical reaction develops) can be anything from house dust to food and even medicines.

Most allergens are of a protein nature (they contain protein components or form amino acids when they enter the human body). But some have nothing to do with amino acids: sunlight (one of the common causes of dermatitis), water, low temperatures.

The most common allergens are:

• plant pollen;
• dust and its components;
• fungal spores;
• medicines;
• food products;
• fragments of saliva of domestic animals.

Allergies can be congenital or acquired.

The attention of the mass reader is offered a book on one of the most pressing problems of our time - allergies. Perhaps there is not a single person who has not heard this strange word. And what does it mean? Is this a disease or a normal manifestation of the body? Why and who gets allergies? Can it be cured? How to live on for a person who has an allergy? All these questions and many more are answered by the author of this book. The reader will learn about the causes of the development and exacerbation of allergies, a variety of methods of treatment and prevention of this condition.

Types of allergic reactions

Depending on the time of occurrence, all allergic reactions can be divided into 2 large groups: if allergic reactions between the allergen and body tissues occur immediately, then they are called immediate-type reactions, and if after a few hours or even days, then these are delayed-type allergic reactions. According to the mechanism of occurrence, 4 main types of allergic reactions are distinguished.

Type I allergic reactions

The first type includes allergic reactions (hypersensitivity) of the immediate type. They are called atopic. Allergic reactions of immediate type are the most common immunological diseases. They affect approximately 15% of the population. Patients with these disorders have abnormal immune responses called atopic. Atopic disorders include bronchial asthma, allergic rhinitis and conjunctivitis, atopic dermatitis, allergic urticaria, angioedema, anaphylactic shock, and some cases of allergic lesions of the gastrointestinal tract. The mechanism of development of the atopic state is not fully understood. Numerous attempts by scientists to find out the causes of its occurrence have revealed a number of characteristics that distinguish some individuals with atopic conditions from the rest of the population. The most characteristic feature of such people is an impaired immune response. As a result of the impact of the allergen on the body, which occurs through the mucous membranes, an unusually high amount of specific allergic antibodies is synthesized - reagins, immunoglobulins E. People with allergies have a reduced content of another important group of antibodies - immunoglobulins A, which are "defenders" of the mucous membranes. Their deficiency opens access to the surface of the mucous membranes to a large number of antigens, which ultimately provokes the development of allergic reactions.

In such patients, along with atopy, the presence of dysfunction of the autonomic nervous system is also noted. This is especially true for people suffering from bronchial asthma and atopic dermatitis. There is an increased permeability of the mucous membranes. As a result of the fixation of so-called reagins on cells with biologically active substances, the process of damage to these cells increases, as well as the release of biologically active substances into the bloodstream. In turn, biologically active substances (BAS) with the help of special chemical mechanisms damage already specific organs and tissues. The so-called "shock" organs in the reaginic type of interaction are primarily the respiratory organs, intestines, and conjunctiva of the eyes. BAS reagin reactions are histamine, serotonin and a number of other substances.

In the reaginic type of allergy, there is a sharp increase in the permeability of the microvasculature. In this case, the fluid leaves the vessels, resulting in the development of edema and inflammation, local or widespread. The amount of discharge of mucous membranes increases, bronchospasm develops. All this is reflected in clinical symptoms.

Thus, the development of immediate type hypersensitivity begins with the synthesis of immunoglobulins E (proteins with antibody activity). The stimulus for the production of reaginic antibodies is exposure to the allergen through the mucous membrane. Immunoglobulin E, synthesized in response to immunization through the mucous membranes, is rapidly fixed on the surface of mast cells and basophils, located mainly in the mucous membranes. With repeated exposure to the antigen, immunoglobulin E fixed on the surfaces of mast cells is combined with the antigen. The result of this process is the destruction of mast cells and basophils and the release of biologically active substances, which, damaging tissues and organs, cause inflammation.

Type II allergic reactions

The second type of allergic reactions is called cytotoxic immune reactions. This type of allergy is characterized by the combination of allergen with cells first, and then antibodies with the allergen-cell system. With this triple connection, cell damage occurs. However, another component is involved in this process - the so-called complement system. Other antibodies are already involved in these reactions - immunoglobulins G, M, immunoglobulins E. The mechanism of damage to organs and tissues is not due to the release of biologically active substances, but due to the damaging effect of the above-named complement. This type of reaction is called cytotoxic. The “allergen-cell” complex can be either circulating in the body or “fixed”. Allergic diseases that have a second type of reaction are the so-called hemolytic anemia, immune thrombocytopenia, pulmonary-renal hereditary syndrome (Goodpasture's syndrome), pemphigus, and various other types of drug allergies.

III type of allergic reactions

The third type of allergic reactions is immunocomplex, it is also called "immune complex disease". Their main difference is that the antigen is not bound to the cell, but circulates in the blood in a free state, without being attached to tissue components. In the same place, it combines with antibodies, more often of classes G and M, forming antigen-antibody complexes. These complexes, with the participation of the complement system, are deposited on the cells of organs and tissues, damaging them. Inflammatory mediators are released from damaged cells and cause intravascular allergic inflammation with changes in surrounding tissues. The above complexes are most often deposited in the kidneys, joints and skin. Examples of diseases caused by reactions of the third type are diffuse glomerulonephritis, systemic lupus erythematosus, serum sickness, essential mixed cryoglobulinemia and prehepatogenic syndrome, which manifests itself with signs of arthritis and urticaria and develops when infected with the hepatitis B virus. Increased vascular permeability plays a huge role in the development of immune complex diseases , which may be exacerbated by the development of an immediate hypersensitivity reaction. This reaction usually proceeds with the release of mast cell contents and basophils.

IV type of allergic reactions

Antibodies do not participate in reactions of the fourth type. They develop as a result of the interaction of lymphocytes and antigens. These reactions are called delayed reactions. Their development occurs 24-48 hours after the allergen enters the body. In these reactions, the role of antibodies is taken by lymphocytes sensitized by the intake of the allergen. Due to the special properties of their membranes, these lymphocytes bind to allergens. In this case, mediators, the so-called lymphokines, are formed and released, which have a damaging effect. Lymphocytes and other cells of the immune system accumulate around the place of entry of the allergen. Then comes necrosis (tissue necrosis under the influence of circulatory disorders) and the replacement development of connective tissue. This type of reaction underlies the development of some infectious-allergic diseases, such as contact dermatitis, neurodermatitis, and some forms of encephalitis. It plays a huge role in the development of such diseases as tuberculosis, leprosy, syphilis, in the development of transplant rejection, in the occurrence of tumors. Often, patients can combine several types of allergic reactions at once. Some scientists distinguish the fifth type of allergic reactions - mixed. So, for example, with serum sickness, allergic reactions of the first (reaginic), second (cytotoxic), and third (immunocomplex) types can develop.

As our knowledge of the immune mechanisms of tissue damage development increases, the boundaries between them (from the first to the fifth type) become more and more vague. In fact, most diseases are caused by the activation of different types of inflammatory responses that are interrelated.

Stages of allergic reactions

All allergic reactions in their development go through certain stages. As you know, getting into the body, the allergen causes sensitization, i.e. immunologically increased sensitivity to the allergen. The concept of allergy includes not only an increase in sensitivity to any allergen, but also the realization of this increased sensitivity in the form of an allergic reaction.

Initially, sensitivity to the antigen increases, and only then, if the antigen remains in the body or enters it again, does an allergic reaction develop. This process can be divided in time into two parts. The first part is preparation, increasing the body's sensitivity to an antigen, or, in other words, sensitization. The second part is the possibility of realizing this condition in the form of an allergic reaction.

Academician A.D. Ado singled out stage 3 in the development of allergic reactions of the immediate type.

I. Immunological stage. It covers all changes in the immune system that occur from the moment the allergen enters the body: the formation of antibodies and (or) sensitized lymphocytes and their combination with the allergen that has re-entered the body.

II. The pathochemical stage, or the stage of the formation of mediators. Its essence lies in the formation of biologically active substances. The stimulus for their occurrence is the combination of the allergen with antibodies or sensitized lymphocytes at the end of the immunological stage.

III. Pathophysiological stage, or stage of clinical manifestations. It is characterized by the pathogenic action of the formed mediators on the cells, organs and tissues of the body. Each of the biologically active substances has the ability to cause a number of changes in the body: dilate capillaries, lower blood pressure, cause spasm of smooth muscles (for example, bronchi), disrupt capillary permeability. As a result, a violation of the activity of the organ in which the incoming allergen met with the antibody develops. This phase is visible to both the patient and the doctor, because the clinical picture of an allergic disease develops. It depends on which way and to which organ the allergen entered and where the allergic reaction occurred, on what the allergen was, and also on its quantity.

Types of allergic reactions

Almost all of us are familiar with various types of allergic reactions. Young children are especially susceptible to the harmful effects of allergens, so all young parents need to know what symptoms this or that type is characterized by and how to properly provide first aid.

In this article, we bring to your attention a modern classification of types of allergic reactions, their symptoms and the necessary tactics for first aid in each case.

Causes of Allergy

In fact, anything can cause an allergy. The body of each person is individual, so any adult or child may develop their own intolerance to a particular product, chemical, and so on.

In most cases, the human immune system responds to the following factors:

• dust - house, street, book, as well as house dust mites;
• pollen of flowering plants;
• pet hair, saliva and secretions;
• mold or fungal spores;
• all kinds of food. Most often, allergic reactions occur after eating citrus fruits, nuts, legumes, eggs, milk and dairy products, honey and seafood;
• bites and excretions of insects, in particular, wasps, bees, ants, bumblebees and others;
• various medicines. The strongest allergens in this category are antibiotics, in particular penicillin, and anesthetics;
• latex;
• sun and water;
• household chemicals.

According to the type of reactions, 4 types of allergies are distinguished, namely:

• anaphylactic reactions of an immediate type appear within a few minutes or 2-3 hours after the interaction of the human body with the allergen. At this moment, a large amount of histamine is released, which has a pronounced physiological effect. This type includes anaphylactic shock, allergic rhinitis, angioedema, atopic bronchial asthma, urticaria and almost all types of allergies in children;
• cytotoxic or cytolytic manifestations. These are reactions that are much slower than the previous type, and necessarily lead to cell death and destruction. These include hemolytic jaundice and anemia of newborn babies as a response of the infant's immune system to the Rh conflict with the mother, complications after the administration of certain drugs, as well as any reactions caused by blood transfusion;
• immunocomplex reactions appear within a day after contact with the allergen. As a result of such processes, damage to the inner walls of the capillaries occurs. Usually, such types of allergies as serum sickness, glomerulonephritis, allergic conjunctivitis, rheumatoid arthritis, systemic lupus erythematosus, hemorrhagic vasculitis and allergic dermatitis are noted here;
• late hypersensitivity can develop within a few days after the negative impact on the human body of certain factors. In most cases, it manifests itself in the form of diseases such as bronchial asthma, rhinitis and contact dermatitis.

Symptoms of different types of allergies

Contrary to popular belief, allergy symptoms do not depend on what exactly served as an allergen in a particular case, but on which organ the inflammatory process began to develop. Depending on the symptoms of the disease, it is possible to determine which organs are inflamed, and what type of allergic reaction is currently observed.

• cough, shortness of breath and various respiratory disorders indicate damage to the respiratory system. As a rule, in this case allergic bronchial asthma develops;
• sneezing, itching of the nasal mucosa, discharge from the nasal cavity, congestion indicate allergic rhinitis;
• excessive lacrimation, itching, redness and swelling of the eyelids indicate conjunctivitis due to allergies;
• an allergic reaction in the form of swelling, for example, behind the ears or in other parts of the body in most cases is angioedema. Also, with this disease, swelling of the mucous membranes and skin can be observed;
• a significant decrease in blood pressure, dizziness, clouding of consciousness, respiratory arrest, fainting almost always indicate anaphylactic shock;
• finally, various allergic reactions in the form of a rash may indicate atopic or contact dermatitis, urticaria and other diseases.

On the various manifestations of allergies in the form of dermatological diseases should be discussed separately.

The main types of allergic reactions that appear on the skin

Depending on the general health of an adult or a child, the following skin reactions may develop in response to contact with some external factors:

• urticaria - the skin with this disease is covered with a huge number of small blisters that resemble nettle burns. In some cases, they grow to large plaques. Such blisters give a sick person a lot of trouble, since they are always accompanied by very strong itching, and if they are combed, then pain will be added to it;
• eczema. With this disease, red rough spots appear on the skin, which also cause quite severe itching. After some time, the foci of inflammation open up and form weeping and scaly erosions. In most cases, eczema affects the face and hands, but by and large it can appear on absolutely any part of the body, for example, behind the ears;
• in atopic dermatitis, tiny watery blisters appear. If an infection gets into the affected area, pyoderma develops. Most adults who are familiar with the manifestations of this disease suffer from exacerbations throughout their lives. In young children, who also often experience atopic dermatitis, the immune system most often suppresses the disease as they grow older;
• neurodermatitis is characterized by the appearance of papular rashes on the skin, which tend to merge and cause a lot of discomfort. Most people suffering from this disease note that they experience increased discomfort in the evening. Usually plaques of neurodermatitis appear on the neck, near the anus, as well as in the elbow and popliteal fossae. Often, with this disease, allergic reactions are also noted in the form of bumps behind the ears, which are inflammation of the lymph nodes. However, such bumps can also indicate other ailments, so if they do not go away for a long time, consult a doctor.

First aid for allergies

First of all, to get rid of the symptoms of allergies, it is necessary to identify the allergen and reduce all contact with it to a minimum. If you cannot do this on your own, see your doctor. Modern laboratory research methods make it possible to determine the allergen with high accuracy using various tests.

• thoroughly wash the place of contact with the allergen, for example, the nasal mucosa, skin or mouth;
• in the presence of a rash, lubricate the skin with an anti-inflammatory cream, for example, "La Cree";
• remove the sting if the allergy is caused by an insect bite;
• apply a cold compress to the itchy area of ​​the skin;
• if breathing is difficult, remove all clothing;
• take an antihistamine, for example, Suprastin or Tavegil. For children, it is better to use drops "Fenistil" or "Zirtek";
• in severe cases, in particular, with the development of Quincke's edema, and also if the medicines do not help, immediately call an ambulance.

Also, be sure to consult a doctor if various allergy symptoms torment you regularly.

In this case, the treatment should be comprehensive and carried out strictly under the supervision of a qualified doctor.

Types of allergic reactions

An allergic reaction is a pathological variant of the interaction of the immune system with a foreign agent (allergen), which results in damage to body tissues.

Immune system: structure and functions

The structure of the immune system is very complex, it includes individual organs (thymus gland, spleen), islets of lymphoid tissue scattered throughout the body (lymph nodes, pharyngeal lymphoid ring, intestinal nodes, etc.), blood cells (various types of lymphocytes) and antibodies (special protein molecules).

Some links of immunity are responsible for the recognition of foreign structures (antigens), others have the ability to remember their structure, and others provide the production of antibodies to neutralize them.

Under normal (physiological) conditions, an antigen (for example, the smallpox virus), when it enters the body for the first time, causes an immune system reaction - it is recognized, its structure is analyzed and remembered by memory cells, and antibodies are produced to it that remain in the blood plasma. The next intake of the same antigen leads to an immediate attack of pre-synthesized antibodies and its rapid neutralization - thus, the disease does not occur.

In addition to antibodies, cellular structures (T-lymphocytes) are also involved in the immune response, capable of releasing enzymes that destroy the antigen.

Allergy: causes

An allergic reaction has no fundamental differences from the normal response of the immune system to an antigen. The difference between the norm and pathology lies in the inadequacy of the ratio of the strength of the reaction and the cause that causes it.

The human body is constantly exposed to various substances that enter it with food, water, inhaled air, through the skin. In the normal state, most of these substances are "ignored" by the immune system, there is a so-called refractoriness to them.

Allergy is an abnormal sensitivity to substances or physical factors, to which an immune response begins to form. What is the reason for the breakdown of the protective mechanism? Why does one person develop a severe allergic reaction to something that the other simply does not notice?

An unequivocal answer to the question about the causes of allergies has not been received. The dramatic increase in the number of sensitized people in recent decades can partly be explained by the sheer number of new compounds they encounter in their daily lives. These are synthetic fabrics, perfumes, dyes, drugs, food additives, preservatives, etc. The combination of antigenic overload of the immune system with innate structural features of some tissues, as well as stress and infectious diseases, can cause a malfunction in the regulation of protective reactions and the development of allergies.

All of the above applies to external allergens (exoallergens). In addition to them, there are allergens of internal origin (endoallergens). Some structures of the body (for example, the lens of the eye) do not come into contact with the immune system - this is required for their normal functioning. But with certain pathological processes (injuries or infections), such natural physiological isolation is violated. The immune system, having detected a previously inaccessible structure, perceives it as foreign and begins to react by forming antibodies.

Another option for the occurrence of internal allergens is a change in the normal structure of any tissue under the influence of burns, frostbite, radiation or infection. The altered structure becomes "alien" and causes an immune response.

Mechanism of an allergic reaction

All types of allergic reactions are based on a single mechanism in which several stages can be distinguished.

1. Immunological stage. The first meeting of the body with the antigen and the production of antibodies to it occurs - sensitization occurs. Often, by the time antibodies are formed, which takes some time, the antigen has time to leave the body, and the reaction does not occur. It happens with repeated and all subsequent receipts of the antigen. Antibodies attack the antigen to destroy it and form antigen-antibody complexes.
2. pathochemical stage. The resulting immune complexes damage special mast cells found in many tissues. These cells contain granules containing inflammatory mediators in an inactive form - histamine, bradykinin, serotonin, etc. These substances become active and are released into the general circulation.
3. Pathophysiological stage occurs as a result of the action of inflammatory mediators on organs and tissues. There are various external manifestations of allergies - spasm of the muscles of the bronchi, increased intestinal motility, gastric secretion and mucus formation, capillary dilation, the appearance of a skin rash, etc.

Clinical picture

What doctors say about antihistamines

Doctor of Medical Sciences, Professor Emelyanov G.V. Medical practice: more than 30 years.
Practical medical experience: more than 30 years

According to the latest WHO data, it is allergic reactions in the human body that lead to the occurrence of most deadly diseases. And it all starts with the fact that a person has an itchy nose, sneezing, runny nose, red spots on the skin, in some cases suffocation.

7 million people die every year due to allergies, and the scale of the lesion is such that the allergic enzyme is present in almost every person.

Unfortunately, in Russia and the CIS countries, pharmacy corporations sell expensive drugs that only relieve symptoms, thereby putting people on one drug or another. That is why in these countries there is such a high percentage of diseases and so many people suffer from "non-working" drugs.

Classification of allergic reactions

Despite the common mechanism of occurrence, allergic reactions have clear differences in clinical manifestations. The existing classification distinguishes the following types of allergic reactions:

I type - anaphylactic , or allergic reactions of immediate type. This type arises due to the interaction of antibodies of group E (IgE) and G (IgG) with the antigen and the sedimentation of the formed complexes on the membranes of mast cells. This releases a large amount of histamine, which has a pronounced physiological effect. The time of occurrence of the reaction is from several minutes to several hours after the penetration of the antigen into the body. This type includes anaphylactic shock, urticaria, atopic bronchial asthma, allergic rhinitis, Quincke's edema, many allergic reactions in children (for example, food allergies).

II type - cytotoxic (or cytolytic) reactions. In this case, immunoglobulins of groups M and G attack antigens that are part of the membranes of the body's own cells, resulting in cell destruction and death (cytolysis). The reactions are slower than the previous ones, the full development of the clinical picture occurs after a few hours. Type II reactions include hemolytic anemia and hemolytic jaundice of newborns with Rhesus conflict (in these conditions, massive destruction of red blood cells occurs), thrombocytopenia (platelets die). This also includes complications during blood transfusion (blood transfusion), the administration of drugs (toxic-allergic reaction).

III type - immunocomplex reactions (Arthus phenomenon). A large number of immune complexes, consisting of antigen molecules and antibodies of groups G and M, are deposited on the inner walls of capillaries and cause their damage. Reactions develop within hours or days after the interaction of the immune system with the antigen. This type of reaction includes pathological processes in allergic conjunctivitis, serum sickness (immune response to serum administration), glomerulonephritis, systemic lupus erythematosus, rheumatoid arthritis, allergic dermatitis, hemorrhagic vasculitis.

IV type - late hypersensitivity , or delayed-type allergic reactions that develop a day or more after the antigen enters the body. This type of reaction occurs with the participation of T-lymphocytes (hence another name for them - cell-mediated). The attack on the antigen is not provided by antibodies, but by specific clones of T-lymphocytes that have multiplied after previous antigen intakes. Lymphocytes secrete active substances - lymphokines that can cause inflammatory reactions. Examples of diseases based on type IV reactions are contact dermatitis, bronchial asthma, and rhinitis.

V type - stimulating reactions hypersensitivity. This type of reaction differs from all previous ones in that antibodies interact with cellular receptors designed for hormone molecules. Thus, antibodies “replace” a hormone with its regulatory action. Depending on the specific receptor, the result of the contact of antibodies and receptors in type V reactions may be stimulation or inhibition of organ function.

An example of a disease that occurs on the basis of the stimulating effect of antibodies is diffuse toxic goiter. In this case, antibodies irritate the receptors of thyroid cells intended for thyroid-stimulating hormone of the pituitary gland. The consequence is an increase in the production of thyroxine and triiodothyronine by the thyroid gland, the excess of which causes a picture of toxic goiter (Basedow's disease).

Another variant of type V reactions is the production of antibodies not to receptors, but to the hormones themselves. In this case, the normal concentration of the hormone in the blood is insufficient, since part of it is neutralized by antibodies. Thus, insulin-resistant diabetes occurs (due to insulin inactivation by antibodies), some types of gastritis, anemia, and myasthenia gravis.

Types I-III combine acute allergic reactions of the immediate type, the rest are of the delayed type.

Allergy general and local

In addition to the division into types (depending on the rate of occurrence of manifestations and pathological mechanisms), allergies are divided into general and local.

With a local variant, the signs of an allergic reaction are local (limited) in nature. This variety includes the Arthus phenomenon, skin allergic reactions (the Overy phenomenon, the Praustnitz-Küstner reaction, etc.).

Most of the immediate reactions are classified as general allergies.

Pseudoallergy

Sometimes there are conditions that are clinically practically indistinguishable from the manifestations of allergies, but in fact they are not. With pseudo-allergic reactions, there is no main mechanism of allergy - the interaction of an antigen with an antibody.

A pseudo-allergic reaction (the outdated name "idiosyncrasy") occurs when food, drugs and other substances enter the body, which, without the participation of the immune system, cause the release of histamine and other inflammatory mediators. The consequence of the action of the latter is manifestations that are very similar to the "standard" allergic reaction.

The cause of such conditions may be a decrease in the neutralizing function of the liver (with hepatitis, cirrhosis, malaria).

Therapy of any diseases of an allergic nature should be dealt with by a specialist - an allergist. Attempts at self-treatment are ineffective and can lead to the development of severe complications.

• Allergy 325
  • Allergic stomatitis 1
  • Anaphylactic shock 5
  • Urticaria 24
  • Quincke's edema 2
  • Pollinosis 13
• Asthma 39
• Dermatitis 245
  • Atopic dermatitis 25
  • Neurodermatitis 20
  • Psoriasis 63
  • Seborrheic dermatitis 15
  • Lyell's syndrome 1
  • Toxidermia 2
  • Eczema 68
• General symptoms 33
  • Runny nose 33

Full or partial reproduction of site materials is possible only if there is an active indexed link to the source. All materials presented on the site are for informational purposes only. Do not self-medicate, recommendations should be given by the attending physician during an internal consultation.

Types of allergic reactions

The human immune system is one of the most complex mechanisms in our body. This system is designed to protect us from various infections and foreign agents. But the excessive load on the immune system, which occurs in the conditions of modern ecology and the abundance of drug therapy, as well as hereditary weakness of the immune system, can lead to the failure of this delicate mechanism. Allergy is one of the manifestations of such a failure. The function of the immune system is the production of antibodies, which are defenders. Their main task is to neutralize substances or pathogens (antigens) that have entered the body. But in fact, the immune system sometimes loses control and begins to react to a harmless substance as dangerous. All this triggers allergic reactions (hypersensitivity). Antigens that are the source of the development of allergic reactions are called allergens.

Nowadays, according to statistics, about half of the world's population suffers from various types of allergies. To protect yourself from the unpleasant manifestations of this disease, it is important to identify in time what kind of allergy bothers you, prevent repeated contact with allergens, and also help the body restore the correct functioning of its defense mechanism.

Allergic reactions have a different manifestation and severity of treatment. At the same time, various organs and tissues of our body can be involved in the process. Allergy can be manifested by spasms of the bronchi, intestines with the development of suffocation, pain, many are familiar with allergic rhinitis, and someone suffers from skin rashes with excruciating itching. All these manifestations are the result of the release of potent biologically active substances into the blood - histamine, serotonin, etc. at the time of the reaction of the allergen with antibodies. These same substances increase the permeability of blood vessels, especially small ones, contributing to the appearance of an inflammatory reaction, swelling of the internal and external mucous membranes or skin.

Allergic reactions often occur against the background of already existing disorders and diseases of other body systems - digestive, nervous, endocrine.

Allergy treatment requires a broad approach to the health of the body as a whole, including cleansing. Folk remedies have their own rich arsenal of means to combat this disease with its various manifestations.

Types of allergic reactions

Allergy can be true and false, manifested by symptoms from various organs and systems.

Sensitization. When you first encounter an allergen, your immune system remembers it. On subsequent contacts, she can immediately recognize the agent and quickly and actively attack him. This process is called sensitization. Such an attack can be clinically manifested by an allergic reaction to certain allergens. It should be noted that in different individuals, the period of time during which sensitization to an allergen is formed can vary from several days to several years.

Atopy. Quite often, patients have atopy - this is an allergy, which is based on hereditary factors. This is usually expressed in a tendency to produce immunoglobulins E (IgE) that react to environmental allergens (plant pollen, dust, animal hair, etc.). Clinically, there are 3 main forms of atopy: atopic dermatitis, hay fever (conjunctivitis, allergic rhinitis, pollen bronchial asthma) and atopic asthma with sensitization to household dust, mites and some other household allergens.

Pseudoallergy. This is a false allergy, but which has similar symptoms (asthma, rhinitis, urticaria, swelling). The body of people who do not have atopy is subjected to sensitization with particular difficulty. With such an allergy, there is no genetic predisposition to the production of IgE. Pseudo-allergic reactions are not immune in nature.

Respiratory allergy, or airway allergy. The cause of this type of allergy are small volatile allergens. These can be mold spores, plant pollen, particles of mites, house dust, particles of animal hair and dander, and others. The reaction is expressed in indomitable sneezing, runny nose, in the form of bronchitis and suffocation. These are allergic conjunctivitis, when the eyes are watery and pursued by severe itching of the eyelids, hay fever, which is seasonal and manifests itself regularly, allergic rhinitis, which manifests itself year-round, as well as bronchial asthma.

Skin allergy. Skin allergy manifests itself in the form of severe itching and burning, rash (swelling, blisters) or eczema (dryness, peeling, change in skin pattern). This allergy can develop as a result of exposure to active toxic substances such as paints, household chemicals, drugs and cosmetics, as well as when food and other similar allergens enter the body through the mucous membrane of the digestive system. They can cause various skin diseases or, as they are also called, allergic dermatosis. It can be eczema, urticaria, atopic dermatitis (exudative diathesis), contact dermatitis.

food allergy. There is a true allergic reaction to food and a pseudo-allergy, which is not based on an immune reaction. This may be food intolerance due to an enzyme deficiency.

Often pseudo-allergic conditions occur against the background of eating, in which histamine is present or it is released during biochemical transformations in the digestive tract. Often this condition is combined with dysbacteriosis (violation of the intestinal microflora). In this situation, you need to seek help from a gastroenterologist, but not an allergist.

True food allergies are based on an immune response. Symptoms can be very different (abdominal pain, vomiting, diarrhea, rhinitis, angioedema, urticaria, eczema, itching, and even anaphylactic shock) and can occur immediately after direct exposure to the allergen, or with a delay. The most common types of food allergies are cow's milk, egg white, chicken, fish, crustaceans (crabs, crayfish, shrimp, etc.), shellfish (oysters, mussels, etc.), as well as certain fruits and vegetables. (strawberries, citrus).

Insect allergy, or allergy to insect bites.

It develops when bitten by insects: bees, wasps, hornets, mosquitoes, midges, etc., as well as when particles of their bodies or waste products are inhaled. An allergy to bites usually manifests itself in the form of edema, as well as an active general reaction (weakness, low blood pressure, urticaria, suffocation, dizziness). Anaphylactic shock may develop, while the general condition deteriorates sharply, weakness occurs, often vomiting, pain and cramps in the abdomen, swelling of the larynx. Then urgent medical attention is needed, otherwise the patient may die. If body particles or waste products of insects (dust mites, moths, cockroaches, etc.) are inhaled into the body, symptoms of bronchial asthma may be observed.

Allergy to drugs. A true allergy to drugs in the form of an immune reaction is quite rare. More common are side effects with overdose, intolerance, pseudo-allergies (when there is no production of antibodies to the drug). So, antihistamines contribute to drowsiness, broad-spectrum antibiotics cause diarrhea against the background of dysbacteriosis.

Most often, drug allergies are caused by:

• Penicillin and its derivatives - sometimes lead to the development of anaphylactic shock, but more often a rash appears.
• Antitetanic and antidiphtheria sera. Previously, they were prepared on the basis of horse blood, which acted as a strong allergen, but now they use human serum, which is much better and easier to tolerate.
• Insulin, which was made from the pancreas of pigs or whales, which was also a strong allergen. Today natural human insulin is used.
• Non-steroidal anti-inflammatory drugs (analgesics, salicylates), enzyme preparations, radiopaque agents, sulfonamides, B vitamins, local painkillers (anesthetics, in particular novocaine).

Drug allergies can manifest themselves in different ways, from mild itching to asthma attacks and severe skin and internal organ lesions. Anaphylactic shock may also develop.

infectious allergy

These are increased reactions of the body to non-pathogenic or opportunistic microbes. To a healthy person, these bacteria are not dangerous, they do not cause the development of the disease. But if you are allergic to one of these microbes, then, for example, infectious-allergic bronchial asthma may develop. Infectious allergy is also closely associated with mucosal dysbiosis.

There is another group of allergies caused by physical factors: allergy to solar radiation (photosensitivity), cold, ultraviolet.

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Drawing conclusions

Allergy is a disease that is characterized by a malfunction of the immune system associated with the recognition of a potential threat to the body. Subsequently, there is a violation of the work of tissues and organs, characteristic of the inflammatory process. Allergies are caused by the body trying to get rid of substances that it considers harmful.

This leads to the development of numerous allergy symptoms:

• Swelling of the throat or mouth.
• Difficulty swallowing and/or speaking.
• Rash anywhere on the body.
• Redness and itching of the skin.
• Abdominal cramps, nausea and vomiting.
• Sudden feeling of weakness.
• A sharp drop in blood pressure.
• Weak and fast pulse.
• Dizziness and loss of consciousness.

Even one of these symptoms should make you think. And if there are two of them, then do not hesitate - you have an allergy.

How to treat allergies when there are a large number of drugs that cost a lot of money?

Most medicines won't do any good, and some can even hurt! At the moment, the only medicine that is officially recommended by the Ministry of Health for the treatment of allergies is this.

Until February 26th. The Institute of Allergology and Clinical Immunology, together with the Ministry of Health, is implementing a program " without allergies". Within which the drug is available for only 149 rubles , to all residents of the city and region!

An allergic reaction is a pathological response of the body's defense system to the influence of an irritant - an allergen. Ultimately, the body begins to synthesize antibodies that are designed to resist allergens, but are perceived by them as hostile.

Thus, antibodies lead not only to the neutralization of the allergen, but also to damage to healthy tissues, provoke various types of allergic reactions. Most often, allergies occur in one form or another of skin dermatosis.

Types of allergic reactions: etiological and provoking factors

The etiological factors that cause the development of different types of allergic reactions are currently not well understood. They are triggered by the earlier sensitization of the body by an allergen (one or more). An allergen is a substance to which the defense system responds with an atypical reaction. Allergens can be any antigens that the body regards as foreign.

All allergens are conditionally divided into 2 groups:

1. infectious:
. particles of bacteria;
. mushroom components;
. components of viruses;
. helminth particles.

2. Non-infectious:
. plant pollen;
. dust (street, book, house);
. detergents and cosmetics (powders, soaps, perfumes, oils, gels, shampoos);
. food products (milk, seafood, chocolate, fish, citrus fruits, honey, nuts);
. wool, skin particles, saliva of animals (mainly cats and dogs);
. chemicals (varnishes, paints, resins, solvents);
. poisons of animal origin (stings of bees, bumblebees, wasps);
. medicines (mainly antibiotics);
. latex (disposable gloves, condoms);
. ultra-violet rays;
. cold;
. synthetic clothing.

Factors provoking various types of allergic reactions

In order to trigger manifestations of an allergic reaction, in addition to exposure to an allergen, one or more provoking factors must occur that significantly increase the risk of an allergy.

The occurrence of an allergic reaction has a direct relationship with the individual susceptibility of the organism. The effect of one allergen on the body of different people is different.

So, for example, one person consumes seafood without consequences, while in another they lead to the development of some type of allergic reaction.

Types of allergic reactions: classification

There are 4 types of allergic reactions:
. First type
This is an immediate reaction, which proceeds according to the anaphylactic type (Quincke's edema, anaphylactic shock, bronchial asthma, allergic rhinitis or urticaria). After exposure to an allergen, the body's response in the form of an allergy is formed after a few minutes - several hours.

. Second type
It proceeds as a cytotoxic reaction, it is based on the cytolysis (destruction) of cells. It develops more slowly, and lasts longer (up to several hours). Manifested by thrombocytopenia, hemolytic anemia, toxic allergies.

. Third type
It is called the Arthus phenomenon and proceeds according to the type of immunocomplex reaction. It is based on the formation of complexes of antibodies and allergens (antigens), which are deposited on the walls of capillaries and destroy them. This reaction continues for several days. Manifested by allergic conjunctivitis, glomerulonephritis, systemic lupus erythematosus, hemorrhagic vasculitis.

. Fourth type
It proceeds according to a delayed type of allergic reaction or late hypersensitization. Develops within at least 24 hours. Manifested by contact dermatitis, rhinitis, asthma.

Types of allergic reactions: skin manifestations

The main manifestations of skin allergic reactions include:

. atopic dermatitis- manifested by dryness, itching and irritation of the skin;

. contact dermatitis- accompanied by hyperemia, swelling, itching of the skin area in contact with the allergen, the appearance of rashes in the form of papules and vesicles;

. hives- similar to a nettle burn and is accompanied by the appearance of hyperemic spots raised above the skin surface, with a tendency to merge, intense itching, weakness, dizziness;

. eczema- manifested by multiple rash in the form of vesicles with serous contents, prone to open and form erosion, and subsequently scabs, scars;

. toxicoderma- accompanied by a profuse rash of a pink or red hue, which later leads to the formation of blisters;

. neurodermatitis- manifested by night itching, rashes in the form of hyperemic spots, which later merge into plaques, swelling of the skin;

. angioedema- accompanied by swelling of the mucous membranes, swelling of the subcutaneous fatty tissue (more often manifested on the face), hoarseness, difficulty breathing, coughing;

. Lyell's syndrome- refers to severe drug allergy, manifested by the appearance of vesicles, which, opening up, form cracks, erosions, ulcers on the skin;

. steven johnson syndrome- proceeds according to the type of exudative erythema with the appearance of a bright red bleeding rash, the appearance of itching, swelling, fever, weakness, myalgia, headaches.
Methods for identifying types of allergic reactions

In order to confirm the diagnosis and identify a specific irritant, various tests and analyzes are performed.

. Blood tests
With the development of allergies in the peripheral blood, an increased level of eosinophils, class E immunoglobulins is detected.

. Skin tests
The patient is injected intradermally with various allergens, their number can be up to 20 varieties. Each allergen is applied to a specific skin area. A positive reaction manifests itself for half an hour in the form of redness, itching and swelling. The more intense the manifestations, the stronger the effect of the allergen for this patient.

You should stop taking antihistamines 48 hours before performing skin tests, because their use can cause false test results.

. Skin tests
Applications of paraffin, petroleum jelly and a number of allergens (chromium, benzocaine, drugs) are applied to the skin. Applications must be kept on the skin for 24 hours. They are used in the diagnosis of contact dermatitis, eczema.
. Provocative tests
It is 100% reliable in establishing the cause of allergies, but the most dangerous method of examination. Provocative tests are performed in a hospital under the supervision of a group of doctors. The alleged allergen is introduced into the digestive tract, nasopharynx, sublingually.

ALLERGY. MAIN TYPES OF ALLERGIC REACTIONS, MECHANISMS OF THEIR DEVELOPMENT, CLINICAL MANIFESTATIONS. GENERAL PRINCIPLES OF DIAGNOSTICS, TREATMENT AND PREVENTION OF ALLERGIC DISEASES.

Exists special type response to an antigen immune mechanisms. This unusual, different form of response to an antigen, which is usually accompanied by pathological reaction, called allergies.

The concept of "allergy" was first introduced by the French scientist C. Pirquet (1906), who understood allergy as modified sensitivity (both increased and decreased) of the body to a foreign substance upon repeated contact with this substance.

Currently in clinical medicine allergies understand the specific hypersensitivity (hypersensitivity) to antigens - allergens, accompanied by damage to their own tissues when the allergen enters the body again.

An allergic reaction is an intense inflammatory reaction in response to safe for the body of the substance and in safe doses.

Substances of an antigenic nature that cause allergies are called allergens.

TYPES OF ALLERGENS.

There are endo- and exoallergens.

Endoallergens or autoallergens are formed within the body and can be primary and secondary.

Primary autoallergens - these are tissues separated from the immune system by biological barriers, and immunological reactions leading to damage to these tissues develop only when these barriers are violated . These include the lens, the thyroid gland, some elements of the nervous tissue, and the genital organs. In healthy people, such reactions to the action of these allergens do not develop.

Secondary endoallergens are formed in the body from its own damaged proteins under the influence of adverse factors (burns, frostbite, trauma, the action of drugs, microbes and their toxins).

Exoallergens enter the body from the external environment. They are divided into 2 groups: 1) infectious (fungi, bacteria, viruses); 2) non-infectious: epidermal (hair, dandruff, wool), medicinal (penicillin and other antibiotics), chemical (formalin, benzene), food (, vegetable (pollen).

Routes of exposure to allergens varied:
- through the mucous membranes of the respiratory tract;
- through the mucous membranes of the gastrointestinal tract;
- through the skin
- by injection (allergens enter directly into the bloodstream).

Conditions necessary for an allergy to occur :

1. Development of sensitization(hypersensitivity) of the body to a certain type of allergen in response to the initial introduction of this allergen, which is accompanied by the production of specific antibodies or immune T-lymphocytes.
2. Re-hit the same allergen, resulting in an allergic reaction - a disease with corresponding symptoms.

Allergic reactions are strictly individual. For the occurrence of allergies, hereditary predisposition, the functional state of the central nervous system, the state of the autonomic nervous system, endocrine glands, liver, etc. are important.

Types of allergic reactions.

By mechanism development and clinical manifestations There are 2 types of allergic reactions: immediate hypersensitivity (GNT) and delayed hypersensitivity (HRT).

GNT associated with the production antibodies - Ig E, Ig G, Ig M (humoral response), is B-dependent. It develops a few minutes or hours after the repeated introduction of the allergen: the vessels dilate, their permeability increases, itching, bronchospasm, rash, and swelling develop. HRT due to cellular reactions cellular response) - the interaction of an antigen (allergen) with macrophages and T H 1-lymphocytes, is T-dependent. It develops 1-3 days after the repeated introduction of the allergen: there is a thickening and inflammation of the tissue, as a result of its infiltration by T-lymphocytes and macrophages.

Currently adhere to the classification of allergic reactions according to Gell and Coombs, highlighting 5 types by the nature and place of interaction of the allergen with the effectors of the immune system:
I type- anaphylactic reactions;
II type- cytotoxic reactions;
III type- immunocomplex reactions;
IV type- Delayed type hypersensitivity.

I, II, III types hypersensitivity (according to Gell and Coombs) refer to GNT. IV type- to HRT. Antireceptor reactions are distinguished into a separate type.

Type I hypersensitivity - anaphylactic, in which the primary intake of the allergen causes the production of IgE and IgG4 by plasma cells.

Development mechanism.

On initial admission the allergen is processed by antigen-presenting cells and exposed to their surface together with MHC class II to present T H 2. After the interaction of T H 2 and B-lymphocyte, the process of antibody formation (sensitization - the synthesis and accumulation of specific antibodies). Synthesized Ig E are attached by the Fc fragment to receptors on basophils and mast cells of the mucous membranes and connective tissue.

On secondary admission The development of an allergic reaction proceeds in 3 phases:

1) immunological- the interaction of existing Ig E, which are fixed on the surface of mast cells with the re-introduced allergen; at the same time, a specific antibody + allergen complex is formed on mast cells and basophils;

2) pathochemical- under the influence of a specific antibody + allergen complex, degranulation of mast cells and basophils occurs; a large number of mediators (histamine, heparin, leukotrienes, prostaglandins, interleukins) are released from the granules of these cells into the tissues;

3) pathophysiological- there is a violation of the functions of organs and systems under the influence of mediators, which is manifested by the clinical picture of allergy; chemotactic factors attract neutrophils, eosinophils and macrophages: eosinophils secrete enzymes, proteins that damage the epithelium, platelets also secrete allergy mediators (serotonin). As a result, smooth muscles contract, vascular permeability and mucus secretion increase, swelling and itching appear.

The dose of antigen that causes sensitization is called sensitizing. It is usually very small, because large doses may cause not sensitization, but the development of immune protection. The dose of antigen administered to an animal already sensitized to it and causing the manifestation of anaphylaxis is called permissive. The resolving dose should be significantly greater than the sensitizing dose.

Clinical manifestations: anaphylactic shock, food and drug idiosyncrasy, atopic diseases:allergic dermatitis (urticaria), allergic rhinitis, pollinosis (hay fever), bronchial asthma.

Anaphylactic shock in humans, it occurs most often with repeated administration of immune foreign sera or antibiotics. Main symptoms: pallor, shortness of breath, rapid pulse, a critical decrease in blood pressure, shortness of breath, cold extremities, swelling, rash, decrease in body temperature, CNS damage (convulsions, loss of consciousness). In the absence of adequate medical care, the outcome can be fatal.

For prevention and prevention anaphylactic shock, the desensitization method according to Bezredko is used (was first proposed by the Russian scientist A. Bezredka, 1907). Principle: the introduction of small permissive doses of the antigen, which bind and remove part of the antibodies from circulation. The way is in that a person who has previously received any antigenic preparation (vaccine, serum, antibiotics, blood products), upon repeated administration (if he has hypersensitivity to the drug), is first administered a small dose (0.01; 0.1 ml ), and then, after 1-1.5 hours - the main dose. This technique is used in all clinics to avoid the development of anaphylactic shock. This admission is mandatory.

With food idiosyncrasy allergies often occur on berries, fruits, spices, eggs, fish, chocolate, vegetables, etc. Clinical symptoms: nausea, vomiting, abdominal pain, frequent loose stools, swelling of the skin, mucous membranes, rash, itching.

Drug idiosyncrasy is hypersensitivity to repeated drug administration. More often it occurs to widely used drugs during repeated courses of treatment. Clinically, it can manifest itself in mild forms in the form of a rash, rhinitis, systemic lesions (liver, kidneys, joints, central nervous system), anaphylactic shock, laryngeal edema.

Bronchial asthma accompanied severe attacks of suffocation due to spasm of the smooth muscles of the bronchi. Increased secretion of mucus in the bronchi. Allergens can be any, but enter the body through the respiratory tract.

Pollinosis - allergy to plant pollen. Clinical symptoms: swelling of the nasal mucosa and shortness of breath, runny nose, sneezing, hyperemia of the conjunctiva of the eyes, lacrimation.

Allergic dermatitis characterized by the formation on the skin of rashes in the form of blisters - bandless edematous elements of a bright pink color, rising above the level of the skin, of various diameters, accompanied by severe itching. Rashes disappear without a trace after a short period of time.

Available genetic predisposition to atopy- increased production of Ig E to the allergen, an increased number of Fc receptors for these antibodies on mast cells, increased permeability of tissue barriers.

For treatment atopic diseases are used desensitization principle - repeated introduction of the antigen that caused the sensitization. For prevention - identification of the allergen and exclusion of contact with it.

Type II hypersensitivity - cytotoxic (cytolytic). Associated with the formation of antibodies to surface structures ( endoallergens) own blood cells and tissues (liver, kidneys, heart, brain). It is caused by antibodies of the IgG class, to a lesser extent by IgM and complement. The reaction time is minutes or hours.

MECHANISM OF DEVELOPMENT. The antigen located on the cell is "recognized" by antibodies of the IgG, IgM classes. In the cell-antigen-antibody interaction, complement is activated and destruction cells by 3 destinations: 1) complement dependent cytolysis ; 2) phagocytosis ; 3) antibody-dependent cellular cytotoxicity .

Complement mediated cytolysis: antibodies are attached to antigens on the cell surface, a complement is attached to the Fc fragment of antibodies, which is activated with the formation of MAC and cytolysis occurs.

Phagocytosis: phagocytes engulf and (or) destroy target cells opsonized by antibodies and complement containing the antigen.

Antibody-dependent cellular cytotoxicity: lysis of target cells opsonized by antibodies using NK cells. NK cells attach to the Fc portion of antibodies that have bound to antigens on target cells. Target cells are destroyed by perforins and NK cell granzymes.

Activated complement fragments involved in cytotoxic reactions ( C3a, C5a) are called anaphylatoxins. They, like IgE, release histamine from mast cells and basophils, with all the corresponding consequences.

CLINICAL MANIFESTATIONS - Autoimmune Diseases due to the appearance autoantibodies to self-tissue antigens. Autoimmune hemolytic anemia due to antibodies to the Rh factor of erythrocytes; RBCs are destroyed by complement activation and phagocytosis. Pemphigus vulgaris (in the form of blisters on the skin and mucous membranes) - autoantibodies against intercellular adhesion molecules. Goodpasture's syndrome (nephritis and hemorrhages in the lungs) - autoantibodies against the basement membrane of the glomerular capillaries and alveoli. Malignant myasthenia gravis - autoantibodies against acetylcholine receptors on muscle cells. Antibodies block the binding of acetylcholine to receptors, leading to muscle weakness. autoimmune thyroidism - antibodies to thyroid-stimulating hormone receptors. By binding to receptors, they mimic the action of the hormone, stimulating the function of the thyroid gland.

type III hypersensitivity- immunocomplex. Based on education soluble immune complexes (antigen-antibody and complement) with the participation of IgG, less often IgM.

Picks: C5a, C4a, C3a complement components.

MECHANISM OF DEVELOPMENT. The formation of immune complexes in the body ((antigen-antibody) is a physiological reaction. Normally, they are quickly phagocytosed and destroyed. Under certain conditions: 1) the rate of formation exceeds the rate of elimination from the body; 2) with complement deficiency; 3) with a defect in the phagocytic system - the resulting immune complexes are deposited on the walls of blood vessels, basement membranes, i.e. structures with Fc receptors. Immune complexes cause activation of cells (platelets, neutrophils), blood plasma components (complement, blood coagulation system). Cytokines are involved, and macrophages are involved in the process in the later stages. The reaction develops 3-10 hours after exposure to the antigen. An antigen can be exogenous or endogenous in nature. The reaction can be general (serum sickness) or involve individual organs and tissues: skin, kidneys, lungs, liver. It can be caused by many microorganisms.

CLINICAL MANIFESTATIONS:

1) diseases caused exogenous allergens: serum sickness (caused by protein antigens), Arthus phenomenon ;

2) diseases caused endogenous allergens: systemic lupus erythematosus, rheumatoid arthritis, hepatitis;

3) infectious diseases accompanied by active formation of immune complexes - chronic bacterial, viral, fungal and protozoal infections;

4) tumors with the formation of immune complexes.

Prevention - exclusion or restriction of contact with the antigen. Treatment - anti-inflammatory drugs and corticosteroids.

Serum sickness - develops with a single parenteral administration large doses of serum and others protein drugs (for example, tetanus toxoid horse serum). Mechanism: after 6-7 days, antibodies appear in the blood against horse protein , which, interacting with this antigen, form immune complexes deposited in the walls of blood vessels and tissues.

Clinically serum sickness is manifested by edema of the skin, mucous membranes, fever, swelling of the joints, rash and itching of the skin, a change in the blood - an increase in ESR, leukocytosis. The timing of manifestation and the severity of serum sickness depend on the content of circulating antibodies and the dose of the drug.

Prevention serum sickness is carried out according to the Bezredki method.

Type IV hypersensitivity - delayed-type hypersensitivity (DTH), caused by macrophages and T H 1-lymphocytes, which are responsible for stimulation cellular immunity.

MECHANISM OF DEVELOPMENT. HRT is called CD4+ T-lymphocytes(subpopulation Tn1) and CD8+ T-lymphocytes, which secrete cytokines (interferon γ), activating macrophages and induce inflammation(via tumor necrosis factor). macrophages are involved in the process of destruction of the antigen that caused sensitization. In some CD8+ disorders, cytotoxic T lymphocytes directly kill the target cell carrying the MHC I + allergen complexes. HRT develops mainly through 1 – 3 days after repeated allergen exposure. going on thickening and inflammation of the tissue, as a result of it infiltration by T-lymphocytes and macrophages.

Thus, after the initial ingestion of the allergen in the body, a clone of sensitized T-lymphocytes is formed that carries specific recognition receptors for this allergen. At re-hit the same allergen, T-lymphocytes interact with it, are activated and secrete cytokines. They cause chemotaxis to the site of allergen injection. macrophages and activate them. macrophages in turn, they secrete many biologically active compounds that cause inflammation and destroy allergen.

With HRT tissue damage happens as a result of products activated macrophages: hydrolytic enzymes, reactive oxygen species, nitric oxide, pro-inflammatory cytokines.Morphological picture wearing HRT inflammatory character, caused by the reaction of lymphocytes and macrophages to the resulting allergen complex with sensitized T-lymphocytes. To develop such changes a certain number of T cells are needed, for what need 24-72 hours , and so the reaction called slow. At chronic HRT often formed fibrosis(as a result of the secretion of cytokines and macrophage growth factors).

DTH reactions may cause the following antigens:

1) microbial antigens;

2) helminth antigens;

3) natural and artificially synthesized haptens (drugs, dyes);

4) some proteins.

HRT is most pronounced on admission low-immune antigens (polysaccharides, low molecular weight peptides) when administered intradermally.

Many autoimmune diseases are the result of HRT. For example, when type I diabetes around the islets of Langerhans, infiltrates of lymphocytes and macrophages are formed; destruction of insulin-producing β-cells occurs, which leads to insulin deficiency.

Drugs, cosmetics, low molecular weight substances (haptens) can combine with tissue proteins, forming a complex antigen with the development contact allergy.

infectious diseases(brucellosis, tularemia, tuberculosis, leprosy, toxoplasmosis, many mycoses) accompanied by the development of HRT - infectious allergy .

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