Activation of platelets by sera containing igg1 heparin-dependent antibodies: an explanation for the predominance of the Fcγrlla “low responder” (his131) gene in patients with heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is a prothrombotic disorder caused by heparin-dependent IgG (HIT-IgG) that recognizes a complex of heparin and platelet factor 4 (PF4), leading to platelet activation via the platelet Fc gammaIIa receptors (Fc gammaRIIa). Not all patients who generate HIT-IgG in response to heparin develop HIT, however, possibly because of observed differences in the ability of platelets from healthy individuals to be …