Change in the body's susceptibility or reactivity to a foreign substance is called allergy (from the Greek. "reaction to someone else"). The name "allergy" was coined by the Austrian scientist Clemens Pirke in 1906. He also suggested that the term be used to describe the effect on the body of various factors from the external environment, and the substances that excite these allergic reactions should be called allergens.
American allergist R. A. Cook in 1947 created the first classification of allergies. By his definition, there is immediate type hypersensitivity and delayed type hypersensitivity. The latter type will be discussed in detail in this article. Importantly, immediate-type and delayed-type hypersensitivity reactions are significantly different from each other.
Main difference
Hypersensitivityimmediate type is a reaction to an antigen that occurs 20-25 minutes after a secondary encounter with an allergen (antigen). A delayed-type hypersensitivity reaction is expressed no earlier than after 7-8 hours or several days. In 1968, P. G. Gell and R. A. Coombs wrote a scientific paper called "A New Classification of Allergic Reactions." According to this classification, 4 main types of allergies are distinguished.
Types of allergies
- 1 type - anaphylactic, atopic, reaginic. The manifestations of this type include Quincke's edema, anaphylactic shock, atopic bronchial asthma, urticaria.
- 2 type - cytotoxic or cytolytic, its manifestations include leukemia, hemolytic anemia, Rh incompatibility.
- 3 type - immunocomplex, or Arthus type. It is estimated by the general reaction and is the main one in the etiology of serum sickness, rheumatoid arthritis, systemic lupus erythematosus. All three of these types are closely related to hemagglutinin and belong to the immediate type of hypersensitivity.
- 4 type - delayed type hypersensitivity, the counteraction mechanism is characterized by cellular action of T-lymphocyte-heller antigen.
Sensitization
Delayed-type hypersensitivity reaction is the body's sensitization to microbial antigens, bacteria, viruses, fungi, helminths, to artificial and natural antigens (chemicals, drugs), to individual proteins. most brightlydelayed-type hypersensitivity responds to the introduction of low immunogenic antigens. A small dose of antigens when injected subcutaneously causes delayed-type hypersensitivity. The mechanism of development of this type of allergic reaction is the hypersensitivity of T-lymphocytes-hellers to antigens. Hypersensitivity of lymphocytes causes the release of substances, for example, interleukin-2, which activate macrophages, the death of the antigen that caused the sensitization of lymphocytes occurs. T-lymphocytes also turn on a defense mechanism that kills bacteria, viruses, or protozoa.
This form of sensitization is seen in many infectious diseases, such as tuberculosis, syphilis, brucellosis, diphtheria, fungal infections, helminthiases and others, as well as transplant rejection.
Example
The most obvious example of such reactions is the Mantoux tuberculin test. If tuberculin is administered intradermally to a person in whose body the tubercle bacillus is located, then after 24-48 hours an induration of 10-15 mm with an abscess in the center will form at the injection site.
Histological examination shows that the infiltrate consists mainly of lymphocytes and cells of the monocyte-macrophage series.
Aneriya
In rare cases, there is no reaction. This is called anergy, that is, the lack of reaction of the body to stimuli.
Positive energy occurs whenthe allergen, getting into the body, dies. This does not cause inflammation.
Negative anergy occurs when the body is unable to defend itself, indicating weakness in the individual. The reason for the lack of reaction or its weak severity may be a decrease in the number of T-lymphocytes or a violation of their functions, and this may also be caused by increased activity of T-suppressors.
Para-allergy and pseudo-allergy
There are concepts of "paraallergy" and "pseudoallergy". They occur when diagnosing infectious diseases expressed by allergic reactions.
Paraallergy is when an infected organism reacts to similar allergens, for example, a tuberculosis infected person reacts to atypical mycobacteria.
A pseudo-allergy is an allergy, for example, to tuberculin in a person with leukemia.
Allergy stages
In the allergic period, 3 stages are described:
- Immunological stage. At this stage, all modifications of the immune system occur. The allergen that enters the body combines with antibodies and hypersensitive lymphocytes.
- Patochemical stage. At this stage, cells form mediators (biologically active chemicals), monokines, lymphokines, which are formed as a result of the allergen being attached to antibodies and hypersensitive lymphocytes.
- Pathophysiological stage. At this stageclinical manifestations of the disease. This happens because the mediators that have appeared have a detrimental effect on the tissues of the body. At this stage, swelling, itching, spasms of smooth muscle tissue, circulatory disorders, etc. are observed.
These stages define delayed-type hypersensitivity.
Treatment
This is one of the most difficult questions. Therapy should be distinct from immediate-type hypersensitivity therapy, as delayed-type hypersensitivity is immune inflammation.
Direction
Treatment should be directed to the immunological moment, anti-inflammatory therapy and neutralization of the pathogen. Nevertheless, therapy must begin with the general rules for the treatment of allergic diseases. Be sure to follow a hypoallergenic diet. In the treatment of this type of hypersensitivity, a special place is occupied by etiological treatment, that is, directed to the cause of the disease.
Types of delayed-type hypersensitivity. Their treatment
This type of hypersensitivity is subdivided into contact, tuberculin and granulomatous, so treatment should be directed to a certain type.
- Contact hypersensitivity occurs when interacting with chemicals (cob alt, nickel, tree resins, mercury, etc.), drugs, poisonous plants. In addition to the main treatment of allergies, in addition to the treatment of contact hypersensitivity, the termination of interaction withcauses of allergies, therapy aimed at relieving inflammation, UV irradiation.
- Tuberculin hypersensitivity is diagnostic and is caused by tuberculin or similar antigens and therefore does not require treatment.
- Delayed-type infectious hypersensitivity occurs when sensitization to microorganisms that cause infectious diseases, such as: tuberculosis, syphilis, brucellosis, anthrax, gonorrhea, parasitic infestations. The treatment of infectious allergies is focused on the destruction of the causative agents of the disease.
- Allergic hypersensitivity to soluble proteins occurs when the immune system is weakened, in which the body does not accept protein compounds such as: milk, fish, eggs, nuts, legumes and some proteins found in cereals. For effective treatment, all foods that cause allergies are excluded from the diet.
- Autoallergic hypersensitivity is when sensitive lymphocytes and own antibodies are produced on the body's own tissues, which cause allergies. There are two types of autoallergic allergies.
The first is when the function of the immune system is not damaged, but an autoallergen occurs, which causes a violation of the immune system. The second is when the immune system fails, not understanding where its proteins are and where they are strangers, so it believes that this is an allergen. Treatment is symptomatic and pathogenetic, which consists in the use of immunosuppressants. Mostly corticosteroids.
Hypersensitivity during transplantation is the destruction of a foreign body introduced into the body. Such an allergy can be prevented by proper selection of a donor, as well as by prescribing various immunosuppressive drugs to suppress the immune system.
Thus, a delayed-type hypersensitivity reaction is significant. The hypersensitivity reaction mechanism is based on inflammation, which helps to stop the infection in the affected areas and create a he althy immune system.
