Responses of the immune system to injury

Three categories of immunotoxic effects are identified: direct immunotoxici ty, hypersensitivity, and autoimmunity. Direct immunotoxicity consists of i mmunosuppression and immunostimulation. Total abrogation of the immune resp onse (immunosuppression) results in more frequent, severe, and often atypic al and relapsing infections and lymphomas. Immunostimulation is associated with febrile reactions, the induction/facilitation of autoimmune diseases a nd allergic reactions to unrelated allergens, and impaired hepatic drug bio transformation. Hypersensitivity is manifested by a variety of symptoms inv olving either antigen-specific or non-antigen-specific humoral and cellular adverse responses. Autoimmune reactions are divided into organ-specific an d systemic reactions. Because of the involvement of many redundant mechanis ms, it is difficult to predict responses of the immune system to a given im munotoxic injury. In laboratory animals, histologic but also functional cha nges are necessary to show evidence of and to predict such adverse response s.