The Immunopathology of Hypersensitivity Reactions

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The Immunopathology of Hypersensitivity Reactions

A. Marinkovich, M.D.

Clinical Associate Professor, Stanford Medical School,

Overactivity of the immune system, either allergy (IgE) or hypersensitivity

(non-IgE) is responsible for more illness than is generally appreciated, even

by the medical profession. The least understood are the non-IgE mechanisms

which involve either immune complex formation (type III of Gell and Combs) or

direct killer T-cell involvement (type IV). Type III reactions may be

localized with a large deposition of antigen at a focal point where immune

complexes

are formed and tissue damage ensues including necrosis. This is termed the

Arthus reaction. A systemic dissamination of antigens will provoke a systemic

inflammentory reaction which is most closely modeled by the well studied

acute and chronic serum sickness reaction. Serum sickness was identified as the

constellation of symptoms which followed the aadministration of antitoxins

(antisera given for infectious disease before the advent of antibiotics) which

were derived from non-human sources, most often horses. Chronic serum sickness

was observed when otherwise heaalthy subjects were given repeat doses of

antisera experimentally over relatively short periods of time. The symptoms

observed in spontaneous and experimental serum sickness included fatigue, rash,

cognitive changes, myositis, arthritis, headache, weight-loss, cardiovascular

symptoms etc., which are often seen during heavy chronic exposure to fungal

spores. The dynamic nature of circulating immune complexes, their complexity,

their rapidly changing exquilibrum patterns aaand their pathogenicity must be

appreciated before the clinican can properly interpret the patterns of

illnes his patients’ describe. The best simple test identifying and thereby

allowing the avoidance of serum sickness is a specific IgE test to a panel of

high

exposure antigens including fungi, food and occupational antigens.