Immunochemical study of incomplete platelet autoantibodies by the anti-globulin consumption test (AGCT) with specific anti-immunoglobulin sera.

The indirect anti-globulin consumption test (AGCT) with specific immunoglobulin antisera (anti-IgG and anti-IgM) has been applied to the immunochemical characterization of incomplete platelet auto-antibodies in 33 patients with idiophatic thrombocytopenic purpura (ITP), systemic lupus erythematosus (SLE) and autoimmune hemolytic anemia (AHA). In these cases indirect AGCT on platelets was positive with polyvalent gamma antiserum. The test with anti-IgG was positive in all cases except two, while always negative with anti-IgM, with no relation to the presence of complete platelet antibodies, the type of disease and the immunochemical type of erythrocyte autoantibodies in AHA patients. These results indicate that the incomplete platelets auto-antibodies were of the IgG class.