Maturation in B lymphocytic leukaemia.

Surface markers were studied serially in two cases presenting as acute B cell lymphocytic leukaemia. The leukaemic lymphocytes in both cases had the mouse erythrocyte receptor (MER) and surface immunoglobulin (SIg) with lambda light chain. Changes interpreted as an increase in immunological differentiation were observed in both, during the course of the disease and its treatment. These changes were loss of MER, increase in density of SIg, and the acquisition of SIgA. Selection of therapy to influence differentiation may ultimately afford better control of the lymphocytic leukaemias.