TRANSIENT LOSS OF PROTEINS CARRYING KELL AND LUTHERAN RED-CELL ANTIGENS DURING CONSECUTIVE RELAPSES OF AUTOIMMUNE THROMBOCYTOPENIA

A patient is described in whom two consecutive relapses of autoimmune thrombocytopenic purpura (AITP) were associated with loss of red cell antigens of the Kell and Lutheran blood group systems respectively. Du ring the second relapse the glycoprotein CD44 and to a lesser extent t he LW antigen were also depressed. Both relapses were associated with concomitant production of IgG antibody recognizing high-frequency dete rminants on the corresponding antigen-carrying protein. Blocking of an tigen sites by these antibodies was not the cause of reduced antigen e xpression, because immunoblotting studies showed absence of Kell prote in during the first relapse, and Lutheran protein during the second. O n both occasions the red cell changes reverted to normal with disappea rance of the antibody as the AITP entered remission. There was no evid ence of clonal lymphocyte expansion as demonstrated using immunoglobul in JH and T cell receptor beta chain probes.