1. an immunologic category of diseases evoked by the deposition of antigen-antibody in the microvasculature. Complement is frequently involved and the breakdown products of complement attract polymorphonuclear leukocytes to the site of deposition. Damage to tissue is frequently caused by “frustrated” phagocytosis by polymorphonuclear cells. Vasculitis or nephritis is common. Other clinical manifestations include fever, arthralgias, and cutaneous eruptions. Arthus phenomenon and serum sickness are classic examples, but many other disorders, including most of the connective tissue diseases, may belong in this immunologic category. Immune complex diseases can also occur during a variety of diseases of known etiology, such as subacute bacterial endocarditis.
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