Release of platelet-activating factor and histamine. I. Effect of immune complexes, complement and neutrophils on human and rabbit mastocytes and basophils.

Immune complexes (ICs) triggered the degranulation of basophils/mastocytes in rabbit and man, thus releasing histamine and platelet-activating-factor. ICs acted upon basophils/mastocytes through complement activation and generation of anaphylatoxins and through release of cationic proteins from polymorphonuclear neutrophils. Anaphylatoxins and cationic proteins were active on human and rabbit mastocytes and on human basophils but not on rabbit basophils. Therefore, a cascade of cell to cell interactions may be envisaged implicating successively neutrophils, basophils and/or mastocytes and platelets. These interactions result in enhanced vascular permeability that allows ICs to be trapped along filtering basement membranes. This sequence could perpetuate the deposition of ICs, initially triggered by degranulation of basophils and mastocytes through the IgE-dependent mechanism, and furnish us with an explanation for the rather poorly understood involvement of platelets in immunopathology.