01.12.2007, 21:24
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Регистрация: 29.07.2004
Город: Москва
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Сообщение от glebdom
как аллерголог аллергологу позволю заметить еще раз, что allergy != anaphylaxis
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Вы же упоминали классификацию Джела-Кумбса? Где же там слово "аллергия", в какой части упоминается?
Цитата:
Type 1 - immediate (or atopic, or anaphylactic)
Type 1 hypersensitivity is an allergic reaction provoked by reexposure to a specific type of antigen referred to as an allergen.[2] Exposure may be by ingestion, inhalation, injection, or direct contact. The difference between a normal immune response and a type I hypersensitive response is that plasma cells secrete IgE. This class of antibodies binds to Fc receptors on the surface of tissue mast cells and blood basophils. Mast cells and basophils coated by IgE are "sensitized." Later exposure to the same allergen, cross-links the bound IgE on sensitized cells resulting in degranulation and the secretion of pharmacologically active mediators such as histamine, leukotriene, and prostaglandin that act on the surrounding tissues. The principal effects of these products are vasodilation and smooth-muscle contraction.
The reaction may be either local or systemic. Symptoms vary from mild irritation to sudden death from anaphylactic shock. Treatment usually involves epinephrine, antihistamines, and corticosteroids. If the entire body gets involved, then anaphylaxis can take place; an acute, systemic reaction that can prove fatal.
Some examples:
Allergic asthma
Allergic conjunctivitis
Allergic rhinitis ("hay fever")
Anaphylaxis
Angioedema
Urticaria (hives)
Eosinophilia
Penicillin
Cephalosporin
[edit] Type 2 - antibody-dependent
In type 2 hypersensitivity, the antibodies produced by the immune response bind to antigens on the patient's own cell surfaces. The antigens recognized in this way may either be intrinsic ("self" antigen, innately part of the patient's cells) or extrinsic (absorbed onto the cells during exposure to some foreign antigen, possibly as part of infection with a pathogen). These cells are recognised by macrophages or dendritic cells which act as antigen presenting cells, this causes a B cell response where antibodies are produced against the foreign antigen.
An example here is the reaction to penicillin where the drug can bind to red blood cells causing them to be recognised as different, B cell proliferation will take place and antibodies to the drug are produced. IgG and IgM antibodies bind to these antigens to form complexes that activate the classical pathway of complement activation for eliminating cells presenting foreign antigens (which are usually, but not in this case, pathogens). That is, mediators of acute inflammation are generated at the site and membrane attack complexes cause cell lysis and death. The reaction takes hours to a day.
Another form of type 2 hypersensitivity is called antibody-dependent cell-mediated cytotoxicity (ADCC). Here, cells exhibiting the foreign antigen are tagged with antibodies (IgG or IgM). These tagged cells are then recognised by natural killer (NK) cells and macrophages (recognised via IgG bound (via the Fc region) to the effector cell surface receptor, CD16 (FcγRIII)), which in turn kill these tagged cells.
Some examples:
Autoimmune hemolytic anemia
Goodpasture's syndrome
Pemphigus
Pernicious anemia (if autoimmune)
Immune thrombocytopenia
Transfusion reactions
Hashimoto's thyroiditis
Graves disease (see type V below)
Myasthenia gravis (see type V below)
Rheumatic fever
Hemolytic disease of the newborn (erythroblastosis fetalis)
Acute transplant rejection
[edit] Type 3 - immune complex
Type 3 hypersensitivity occurs when antigens and antibodies are present in roughly equal amounts, causing extensive cross-linking. Large immune complexes that cannot be cleared are deposited in vessel walls and induce an inflammatory response. The reaction can take hours, days, or even weeks to develop.
Some clinical examples:
Rheumatoid arthritis
Immune complex glomerulonephritis
Serum sickness
Subacute bacterial endocarditis
Symptoms of malaria
Systemic lupus erythematosus
Arthus reaction
Farmer's lung (Arthus-type reaction)
[edit] Type 4 - cell-mediated (delayed-type hypersensitivity, DTH)
See also: Cell mediated immunity
Type 4 hypersensitivity is often called delayed type as the reaction takes two to three days to develop. Unlike the other types, it is not antibody mediated but rather is a type of cell-mediated response.
CD8+ cytotoxic T cells and CD4+ helper T cells recognise antigen in a complex with either type 1 or 2 major histocompatibility complex. The antigen-presenting cells in this case are macrophages which secrete IL-12, which stimulates the proliferation of further CD4+ T cells. CD4+ T cells secrete IL-2 and interferon gamma, further inducing the release of other Type 1 cytokines, thus mediating the immune response. Activated CD8+ T cells destroy target cells on contact while activated macrophages produce hydrolytic enzymes and, on presentation with certain intracellular pathogens, transform into multinucleated giant cells.
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