Biological function of gamma E antibodies and mechanisms of reaginic hypersensitivity.

Human reaginic antibodies in sera of atopic individuals are associated with immunoglublin E which represents a distinct immunoglobulin class. The γE antibody agglutinated red cells coated with antigen, indicating that the antibodies are probably divalent. However, the antibodies do not have complement-fixing activity. The antibodies are responsible for P–K reactions in humans, passive cutaneous anaphylaxis reactions in monkeys and sensitize human leucocytes and monkey lung tissues, but not the guinea-pig skin. Immunoglobulin E combines with the tissues which are involved in the reaginic hypersensitivity reactions through the Fc portion of the molecules. The initial step in hypersensitivity reactions is probably bridging of cell-bound γE molecules which induce structural changes in these molecules. These changes may induce enzymatic sequences leading to the release of histamine and/or slow reacting substance of anaphylaxis depending on the cells involved. Studies on the distribution of γE forming cells indicated that these cells localized in respiratory and gastro-intestinal tracts. The results suggested that locally formed γE may play an important role in allergic diseases.