Expression and modulation of common acute lymphoblastic leukaemia antigen by B prolymphocytic leukaemia cells.

Leukaemic blood lymphocytes from patients with B prolymphocytic leukaemia express the common acute lymphoblastic leukaemia antigen (CALLA). The in vitro incubation of prolymphocytes with leucocyte conditioned medium produced the acquisition of plasma cell morphology, of intracytoplasmic immunoglobulins and the simultaneous reduction of CALLA expression. The presence of CALLA appears to be unrelated to different clinical courses. Our report demonstrates that the antigen is present also in relatively mature stages of B lymphocyte differentiation. The blastic appearance of prolymphocytes could suggest that CALLA may be related to active metabolism or function of these cells.