The erythrocyte-coating substance in autoimmune hemolytic disease: its nature and significance.

W HEN THRICE-WASHED RED CELLS are agglutinated by rabbit anti-human-globulin sera (Coombs’ reagent), they are said to be “coated” with an “incomplete” (blocking) antibody.1 Such coating occurs in vivo in erythroblastosis fetalis as a result of placental transfer of maternal isoantibody, and in acquired hemolytic anemia of the immunologic variety2 (“autoimmune” hemolytic disease ) as a result of unknown mechanisms. It may also occur in vitro by exposure of red cell suspensions to antisera containing incomplete antibodies of the appropriate specificity. Despite the sensitive serologic methods”2’4’5 now available for the detection of the “incomplete” antibody bound to the erythrocyte surface in autoimmune hemolytic disease, study of the nature of this “erythrocyte-coating substance” has been greatly impeded by the difficulties inherent in obtaining significant amounts of this material free of contamination by serum proteins or red cell stromata. This report deals with studies of the coating substance eluted from the red cells of autoimmune hemolytic disease, with particular reference to possible differences in serologic properties of the “erythrocytecoating substance” (ECS) in idiopathic and symptomatic#{176} autoimmune hemolytic disease (AIHD) and in cases with “warm” as contrasted with “cold” autoantibodies.