Allergies are becoming a problem for many people of all ages. Its high-quality treatment, prevention of seizures depends on the timely established substance that causes an inadequate reaction of the body when interacting with it. In some cases, a person develops delayed-type allergic reactions. Then high-quality diagnostics becomes the basis for maintaining he alth.
Inadequate answer
Everyone has heard of allergies. But only those who have encountered such a he alth problem firsthand know that there are immediate and delayed allergic reactions. But in any case, this is a serious violation of well-being, which can cause death in the event of an acute development of an allergy attack and untimely medical assistance.
The mechanisms of the occurrence of an inadequate reaction of the body to certain substances, although studied, are not yet fully understood. Closely related to allergieshypersensitivity is defined as an excessive unwanted reaction of the body's immune system to any substance. Initially, it was hypersensitivity that was divided into two types according to the speed of occurrence. Then the allergy received such a division. Delayed-type allergic reactions include processes that occur as a stimulation of cellular immunity in response to the interaction of an antigen with macrophages and type 1 T-helpers.
Typical division
Scientific research on hypersensitivity and allergy has come a long way, as a result of which 4 types of allergic reactions have been identified:
- anaphylactic;
- cytotoxic;
- precitipine;
- delayed hypersensitivity.
Anaphylactic type is an immediate type reaction that develops after only 15-20 minutes after the contact of reagin antibodies with allergens, as a result of which special biologically active substances are released into the body - mediators, for example, heparin, histamine, serotonin, prostaglandin, leukotrienes and others.
Cytotoxic reaction is associated with hypersensitivity to medications. It is based on the combination of antibodies with modified cells, which leads to the destruction and removal of the latter.
The third type of hypersensitivity is also called immunocomplex. This is due to the repeated ingestion of a large amount of soluble proteins into the body, for example, during blood or plasma transfusion, during vaccination. The same reaction is possible withinfection of blood plasma with fungi or microbes, against the background of the formation of proteins due to neoplasms, infections, infection with helminths, and some other pathological processes.
The fourth type of allergic reactions combines the consequences of the interaction of T-lymphocytes and macrophages with carriers of a foreign antigen and is called tuberculin, infectious-allergic, cell-mediated. Another name for this hypersensitivity, which has become the most common, is a delayed-type reaction. It is characteristic of contact dermatitis, rheumatoid arthritis, tuberculosis, leprosy, salmonellosis and other diseases and pathologies. It is by the type of allergen that the classification of delayed-type allergic reactions is carried out.
Do allergies have speed?
Specialists define hypersensitivity as a result of a violation of the body's immune response mechanism. And it is the speed, as well as the mechanisms of development, that determine the differences between allergic reactions of an immediate and delayed type. Initially, experts noticed that different allergen substances can cause a reaction on the body after a different period of time. So delayed-type allergic reactions develop after 12-48 hours. And immediate-type hypersensitivity appears 15-20 minutes after contact with the allergen.
Classification of a delayed-type allergic reaction
In order to better understand the essence of delayed-type allergies, you should study itclassification, because it is in the structuring of an inadequate response of the body's immune system that its main aspects are reflected:
- Contact: a characteristic manifestation is skin dermatitis. It develops a day or two after contact with the allergen, lymphocytes and macrophages participate in its development. The main characteristic of the manifestation is tissue edema.
- Tuberculin appears after 6-48 hours, lymphocytes, macrophages, monocytes are involved.
- Granulomatous - this type of reaction develops after 21-28 hours, macrophages, epithelioid cells are determined in development. Manifestation - fibrosis.
The mechanism of development of a delayed-type allergic reaction is basically similar to the mechanism of cellular immunity. The difference between them can be determined by the end result: if the allergic reaction did not lead to tissue damage, then we can talk about cellular immunity.
Substances-allergens
Most often it is believed that allergens are certain substances that can cause an inadequate reaction of the body's immune system upon contact with them. But allergens include those substances that can potentiate allergens. An inappropriate reaction of the immune system, called an allergy, occurs when interacting with the following substances:
- dust;
- dust mites;
- foreign proteins (donor plasma and vaccines);
- pollen;
- mold;
- drugs: penicillins, salicylates; sulfonamides, local anesthetics;
- food: legumes, sesame, honey, milk, seafood,nuts, citrus fruits, eggs;
- bites of insects, arthropods;
- animal products: animal skin particles (epithelial flakes), wool, cockroaches, house mites;
- chemicals - latex, cleaning products, nickel compounds.
This is not a complete list, even the allergen groups are difficult to list, not to mention the line of each group. It is constantly updated, expanded and refined. Therefore, most likely, delayed-type allergic reactions include not only already identified he alth problems, but also some others that have not yet been differentiated as hypersensitivity.
How does a delayed reaction to an allergen develop?
Any process, including human allergy, goes through several stages in its development. An allergic reaction of a delayed type proceeds as follows: sensitization; then the appearance in the regional lymph nodes of a large number of pyroninophilic cells, from which, in turn, sensitized immune lymphocytes are formed. These cells serve as the so-called transfer factor and, circulating in the blood, are carried through the tissues. The next contact with the allergen activates them with the formation of the allergen-antibody immune complex, which causes tissue damage.
Science has not yet been able to figure out the nature of antibodies in HRT. Studying this type of allergy in animals, scientists noted that the passive transfer of delayed allergies from animal to animal is possible only with the help of cell suspensions. But with blood serum, such a transfer is practically impossible, the presence ofat least a small number of cellular elements.
The development of a delayed type of allergy is impossible, apparently, without cells of the lymphoid series. Blood lymphocytes are capable of serving as carriers of hypersensitivity to biological substances such as tuberculin, picryl chloride, and other allergens. Sensitivity upon contact is passively transmitted by cells of the thoracic lymphatic duct, spleen. A remarkable relationship has been established between the lack of the ability to develop delayed-type allergies and insufficiency of the lymphoid system.
For example, patients with lymphogranulomatosis do not suffer from delayed allergies. Science has supposedly concluded how exactly lymphocytes are the main carriers and carriers of antibodies in delayed allergies. The presence of such antibodies on lymphocytes is also evidenced by the fact that, with delayed allergies, they are able to fix the allergen on themselves. However, many processes occurring in the human body, for various reasons, have not yet been studied enough.
Reaction mediators
The occurrence of any type of allergy is a complex mechanism in which many substances are involved. So delayed-type allergy develops with the help of so-called mediators. Here are the main ones:
- Blastogenic factor that accelerates the transformation of lymphocytes into blasts.
- Lymphotoxin is a protein with a molecular weight of 70000-90000. This compound inhibits growth or causesdestruction of lymphocytes, as well as proliferation (growth) of lymphocytes. This delayed-type allergy mediator inhibits DNA synthesis in humans and animals.
- The macrophage migration inhibition factor is also a protein with a mass of 4000-6000. This biologically active substance affects the speed of movement of macrophages in tissue culture, slowing it down.
In addition to these structures, scientists have identified several other mediators of delayed-type allergy in animals. They have not yet been found in humans.
Discovery history
At the end of the 19th century, the microbiologist R. Koch noticed the relationship between the delayed occurrence of hyperergy and contact with certain substances. The same observation was made by the Viennese pediatrician Clemens von Pirke, noting in children the relationship between exposure to certain substances and deterioration in well-being. The study of the inadequate reaction of the human body to contact with some components of nature, everyday life, and production continues.
In the early 60s of the last century, British immunologists Jell and Coombs identified 4 main types of hypersensitivity reactions. For a long time it was believed that an inadequate response of the immune system is caused by impaired functionality of immunoglobulins E. But then it was found that such a reaction is based on a complex of mechanisms for the interaction of the human body and various components. Therefore, the term "allergy" was reserved for the first of the above types of hypersensitivity.
Symptomatic pathologies
Delayed-type allergic reactions are manifestations of fairly familiar symptoms:
- Infectious allergy resulting from exposure to microorganisms that can cause brucellosis, gonorrhea, syphilis, tuberculosis, anthrax.
- Tuberculin hypersensitivity is familiar to everyone, like the Mantoux test, which allows to detect infection with the Koch bacillus.
- Protein allergy - hypersensitivity to food - eggs, milk, fish, nuts, legumes, cereals.
- Autoimmune allergy - the inability of the immune system to distinguish between its own substances and foreign substances, reacting to them as to allergens.
Features of HRT
The studied mechanisms of delayed-type allergic reactions are based on two main forms of T-cell immune response. Sensitization occurs first.
From the place where the allergen enters the lymph node, regional in relation to this place, the migration of white process epidermocytes (Langerhans cells) or dendritic cells of the mucous membranes begins, moving the peptide fragment of the antigen as part of the MHC class II membrane molecules.
Then there is a reaction of a certain group of lymphocytes and their response in the form of proliferation, differentiation into Th1 cells. When the antigen enters the body again, already sensitized lymphocytes react, activating first resident and then migrating macrophages. This process causes the development of inflammation, in which cellular infiltration dominates vascular changes.
Herea special role is assigned to the humoral products of effector cells - cytokines. As a result of immune defense against cell damage upon contact with the allergen, delayed-type hypersensitivity becomes a damaging factor in the body. For example, granulomatous reaction in tuberculosis: macrophages and T-lymphocytes surround the cells with the pathogen, forming a protective granuloma. Inside this formation, the cells die, which leads to the disintegration of tissues according to the caseous type. So the protective reaction of the body turns into a damaging one.
Typical diseases
Delayed allergic reactions appear no earlier than 6-24 hours after contact with the allergen. In this case, the diagnosis is made with a specific problem based on the symptoms:
- Hansen's disease;
- gonorrhea;
- phototoxic dermatitis;
- allergic conjunctivitis;
- mycosis;
- syphilis.
Delayed-type allergic reactions also include graft rejection and antitumor immunity response. Only a specialist can determine the exact causes of a he alth problem after a thorough and high-quality diagnosis.
Diagnosis
Delayed-type allergic reactions develop according to mechanisms similar to cellular immunity. For their correct treatment, reliable diagnostics is necessary, because it is she who will help to identify the substance that causes an inadequate reaction. Suchthe determination is carried out using allergic tests - biological reactions used in diagnostics and based on the increased sensitivity of the body to a certain allergen.
Such a study is carried out according to two methods - in vivo and in vitro. The first in vivo is carried out directly with the patient. The second is outside the body, such a test or study is also called an "in vitro" reaction. In both cases, allergens act as diagnostic tests. The well-known Mantoux reaction refers specifically to the in vivo study, when Mycobacterium tuberculosis is injected subcutaneously. If the body is sensitized with Koch's wand, then the answer will be inadequate: the skin at the injection site turns red, swells. According to the size of the infiltrate, the specialist registers the result of the test.
How and what to treat?
Delayed-type allergic reactions - an inadequate response delayed by time to the interaction of the human body and irritating substances. Treatment of this type of problem is carried out only on the recommendation of a specialist - an allergist and an immunologist. To cure such a problem, therapy with drugs that stop systemic diseases of the connective tissue, as well as immunosuppressants is used.
The first group of drugs used in the treatment of HRT include:
- glucocorticoids, e.g. Dexamethasone, Prednisolone, Triamcinolone;
- non-steroidal anti-inflammatory drugs such asDiclofenac, Indomethacin, Naproxen, Piroxicam.
Immunosuppressant drugs used for delayed-type allergic reactions are divided into the following groups:
- cytostatics - "Azathioprine", "Mercaptopurine", "Cyclophosphamide";
- anti-lymphocyte serum, anti-lymphocyte globulin and human anti-allergic immunoglobulin;
- slow-acting antirheumatic drugs ("Hingamin", "Penicillamine");
- antibiotics - "Cyclosporin A".
Any drug should only be recommended by your doctor!
Allergic reactions of immediate and delayed type are a serious he alth problem that requires high-quality diagnostics and proper complex treatment. Delayed hypersensitivity reactions occur at the cellular level, changing the structure of tissues and causing their destruction, which can cause disability and death without proper therapy. Only an attentive attitude to one's he alth and timely diagnosis of the disease, followed by high-quality treatment, will give a positive result.
