Chronic lymphocytic leukaemia cells activated in vitro reveal cellular changes that characterize B-prolymphocytic leukaemia and immunocytoma.

Leukaemic blood lymphocytes from a patient in the terminal stage of chronic lymphocytic leukaemia (CLL) according to the Kiel classification were stimulated by lipopolysaccharide from Escherichia coli. During progression to blast transformation, stimulated cells lost receptors for mouse erythrocytes (MRBC), accumulated intracellular Ig (cIg), and expressed more surface membrane immunoglobulin (SmIg). In addition, transforming cells expressed receptors for the monoclonal antibody FMC7, known to distinguish between CLL cells and prolymphocytic leukaemia (B-PLL) cells. Thus, activation of the patient's CLL cells induced changes in the cellular phenotype so as to resemble B-PLL. Some clonal cells progressed further to a secretory stage of differentiation. Thus, in vitro stimulation induced cellular changes reminiscent of not only B-PLL but also immunocytoma. Further studies of this kind may elucidate the relationship between these lymphocytic malignancies.