Monomeric IgG preparations for intravenous use inhibit platelet stimulation by polymeric IgG

Abstract

Seven different IgG preparations for i.v. use were tested for their capacity to inhibit serotonin-release from washed human platelets induced by IgG coupled with bis-diazobenzidine. Using a reference standard consisting of the top 3rd fraction of an ultracentrifuged .gamma.-globulin preparation for i.m. use, 2 chemically treated preparations were less potent inhibitors than the standard while 2 preparations, 1 pH 4 treated and another albumin protected, were better inhibitors. A pepsin treated preparation was devoid of inhibitory capacity, whereas Fc fragments derived from human IgG were extremely efficient. The inhibitory capacity evidently is inversely correlated to the content of olio- and/or dimeric IgG molecules.