Anti-thymocyte globulin induced thrombocytopenia.

Anti-thymocyte globulin is strongly reactive with platelets as measured by flow cytometric analysis. This reactivity appears to be independent of human leukocyte antigen (HLA) phenotype, is dose-dependent with saturation of platelet binding sites readily achieved with concentrations of horse anti-thymocyte globulin (ATG) at 0.25 mg per ml, and cannot be blocked with human anti-PLA1 antibody nor with heat-aggregated human IgG. Results of immunoblot studies after electrophoresis of platelet membrane proteins are consistent with the proposal that horse ATG contains antibodies specific for platelet glycoproteins V and IIa.