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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 throbocytopenic purpura (AITP) were associated with loss of red cell antigens of the Kell and Lutheran blood group systems respectively. During the second relapse the glycoprotein CD44 and to a lesser extent the LW antigen were also depressed. Both relapses were associated with concomitant production of IgG antibody recognizing high‐frequency determinants on the corresponding antigen‐carrying protein. Blocking of antigen sites by these antibodies was not the cause of reduced antigen expression, because immunoblotting studies showed absence of Kell protein during the first relapse, and Lutheran protein during the second. On both occasions the red cell changes reverted to normal with disappearance of the antibody as the AITP entered remission. There was no evidence of clonal lymphocyte expansion as demonstrated using immunoglobulin JH and T cell receptor β chain probes.