Antibody-mediated thrombosis: relation to the antiphospholipid syndrome

Various forms of antibody-mediated thrombosis are presented and the mechanisms involved in their pathogenesis are discussed. Antibody-mediated thrombosis includes heparin-induced thrombocytopenia and thrombosis, autoantibodies to von Willebrand factor mimicking an antiphospholipid syndrome, thrombosis following injection of the murine monoclonal antibody OKT3, hyperacute and acute xenograft rejection, and varicella-associated antibody against protein S. In several of these entities the pathogenesis of thrombosis is closely related to development of cellular procoagulant activity through tight occupancy of Fc receptors, or through complement activation, or through cell-cell interactions. Integrating the antiphospholipid syndrome into the more general category of antibody-mediated thrombosis may provide some hints as to how we could approach the study of those intriguing patients who have the clinical features of the antiphospholipid syndrome but lack those antibodies that currently characterize it.