Analytical Studies on Red Blood Cell Autoantibody and Platelet-associated IgG in Autoimmune Hemolytic Anemia and Evans' Syndrome

Abstract

Red blood cell autoantibodies were analyzed by antiglobulin tests using monospecific antisera to IgG, C_3d or C_3bd C₄ in 19 cases of autoimmune hemolytic anemia (AIHA).
In the Evans' syndrome, platelet-associated IgG (PAIgG) as well as red blood cell autoantibodies were measured by means of complement lysis inhibition assay. Autoantibodies bound to the patients' RBC in 9 cases of 13 uncompensated AIHA were found to be IgG and C_3d. When the AIHA patients having the RBC autoantibodies of IgG plus complement components were treated by glucocorticoids, immunosuppressants or irradiation therapy, the C_3d bound to the patients' RBC disappeared firstly as the increased hemolysis was gradually improved, and then the IgG autoantibodies bound to the patients' RBC reduced to vanish. These results apparently indicate that the increased hemolysis in AIHA is caused by autoantibodies to RBC consisting of IgG plus complement components. The PAIgG was increased from 35.1±16.7 ng/10⁷ platelets to 142∼202 ng/10⁷ platelets in three cases of Evans' syndrome, which RBC was bound by IgG and C_3d. Based on these findings, it is suggested that the thrombocytopenia is caused by antiplatelet autoantibodies and the increased hemolysis is caused by RBC autoantibodies consisting of IgG and complement components in Evans' syndrome.