[Suppression of thrombocyte aggregation by immune complexes. II. The effect of preformed immune complexes on...

The authors studied the pattern of changes in human platelet aggregation (PA) during platelet interaction with soluble immune complexes. Addition of antisera to human IgG and IgM to platelet plasma led to ADP-induced PA suppression. Analogous suppression of human PA was detected upon exposure to xenogenous immune complexes formed during incubation of guinea-pig blood serum with rabbit serum against guinea-pig gamma-globulin. PA was suppressed to a lesser degree upon antigen excess and was suppressed negligibly upon antibody excess. Activation and inactivation of complement did not affect the degree of PA suppression with immune complexes. Suppression of human PA with immune complexes attests to the existence of a previously unknown phenomenon apparently caused by platelet blockade by soluble immune complexes.