HIGHER PROLIFERATIVE RESPONSE IN B-CHRONIC LYMPHOCYTIC-LEUKEMIA (B-CLL) AS COMPARED TO B-MONOCLONAL LYMPHOCYTOSIS OF UNDETERMINED SIGNIFICANCE (B-MLUS) AFTER STIMULATION WITH STAPHYLOCOCCUS-AUREUS AND ANTI-CD40 MONOCLONAL-ANTIBODIES

B-CLL is a malignant monoclonal B-cell disorder and B-MLUS is the beni gn counterpart. The proliferative response and the capacity to secrete IgM was measured in B-CLL and B-MLUS, respectively, and compared to n ormal B-cells. SAC and a mAb against CD40 were used as stimulatory age nts. No cell population responded to anti-CD40 mAb alone. SAC only ind uced a high DNA synthesis rate in normal B-cells as well as in B-CLL c ells, although the magnitude was three-fold lower and delayed for abou t 48 h in B-CLL. B-MLUS cells did not proliferate in response to SAC. The combination of anti-CD40 and SAC enhanced the proliferative capaci ty of normal B-cells and produced a more rapid response in B-CLL. B-ML US cells were not activated. Normal B-cells and B-MLUS did not secrete IgM after SAC stimulation, while B-CLL cells had a continuous increas e in the IgM production during a 6-day culture period. The higher prol iferative capacity of B-CLL cells compared with B-MLUS cells may be ex plained by an increased expression of activation molecules e.g. recept ors for various cytokines and growth factors. Moreover, the inertness and inability of B-MLUS cells in comparison to normal B- and B-CLL cel ls to respond to powerful activation signals might indicate an intrins ic defect of B-MLUS cells in the signal transduction leading to a bloc k of mitosis and a benign course of the disease.