Hypersensitivity Antigens

In type III or immunocomplex-mediated allergy, IgG antibodies form complexes with antigen. At low exposures, the body is able to remove diese complexes, but if there is a severe exposure, immunocomplexes release a variety of proinflammatory cytokines. The involvement of this mechanism is clearest in serum sickness. This mechanism is also considered to be most important in the development of extrinsic allergic alveolitis (hypersensitivity pneumonitis, especially... 

Association of pyrazolone drug hypersensitivity with HLA-DQ and DR antigens. Clin Exp Allergy 1998 28 1153-1158. 

IgE Mediates immediate hypersensitivity by causing release of mediators from mast cells and basophils upon exposure to antigen (allergen). Defends against worm infections by causing release of enzymes from eosinophils. Does not fix complement. Main host defense against helminthic infections. 

Not all antigen-antibody reactions are of benefit to the body, as sometimes the complexes (or their subsequent interaction with body tissues) may result in tissue damage. This must be regarded as a malfunction of the immune system and is known as a hypersensitive reaction. These reactions can be categorized into five main types. The first three involve the interaction between antigen and humoral antibody, and as the onset of the reaction is rapid, the condition is termed immediate hypersensitivity. The fourth type (delayed hypersensitivity) involves T cells and the symptoms of the reaction appear after 24 hours. The fifth type is where antibody stimulates cell function. 

Zimmerman, L.E. and Silverstein, A.M. (1959). Experimental ocular hypersensitivity histopathological changes observed in rabbits receiving a single injection of antigen into the vitreous. Am. J. Ophthalmol. 48, 447-465. 

Allergic contact dermatitis is a delayed hypersensitivity reaction.30 Upon initial exposure, a substance penetrates the skin, binds to a protein and develops into sensitizing antigens. Subsequent exposures to that substance will then elicit an allergic reaction.25,29,30 Symptoms of allergic contact dermatitis are similar to those of the irritant type, but may take several hours to several days to develop following re-exposure.25,26... 

Eosinophil 1 %—4% Antigen-antibody reactions Eosinophilia Hypersensitivity reactions, including medications Parasitic infections... 

Anaphylactic/anaphylaxis Immediate, severe, potentially fatal hypersensitivity reaction induced by an antigen. 

Atopy A genetic predisposition to develop type I hypersensitivity reactions against common environmental antigens commonly seen in patients with allergic rhinitis, asthma, and atopic dermatitis. 

The answers are 25-e, 26-b, 27-a. (Hardmanr pp 67—68. Katzung, pp 30, 134.) Anaphylaxis refers to an acute hypersensitivity reaction that appears to be mediated primarily by immunoglobulin E (IgE). Specific antigens can interact with these antibodies and cause sensitized mast cells to release vasoactive substances, such as histamine. Anaphylaxis to penicillin is one of the best-known examples the drug of choice to relieve the symptoms is epinephrine. 

Delayed cutaneous hypersensitivity is commonly assessed using antigens to which the patient has been previously sensitized. The recall antigens used most frequently are mumps, Candida albicans, streptokinase-streptodornase, Trichophyton, coccidioidin, and purified protein derivative. Anergy is associated with malnutrition. 

In addition to tumor immunity, UV exposure was found to impair antigen presenting cell function, the generation of contact hypersensitivity (CHS) to chemical haptens and... 

Kim, T. H. et al., Viability of the antigen determines whether DNA or urocanic acid act as initiator molecules for UV-induced suppression of delayed-type hypersensitivity, Photochem. Photobiol. 78, 228-234, 2003. 

Nierkens, S. et al., Development of an oral exposure mouse model to predict drug-induced hypersensitivity reactions by using reporter antigens. Toxicol. Sci., 83, 273, 2005. 

Hypersensitivity (allergy) is defined as humoral or cellular responses to an otherwise innocuous antigen, which can lead to tissue damage. Hypersensitivity reactions... 

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