LEUKEMIC-CELLS FROM PROGRESSIVE B-CLL RESPOND STRONGLY TO GROWTH-STIMULATION IN-VITRO

Isolated leukemic B cells from patients with B-chronic lymphocytic leu kemia (B-CLL) were tested for proliferative response in vitro to Staph ylococcus Aureus strain Cowan 1 (SAC), IL-2, and low molecular weight (MW) BCGF. Patients were classified according to clinical stage and pr ogressiveness. Ten of eighteen cell populations from patients with pro gressive B-CLL responded in vitro with a stimulation index (SI) >20. O nly 1/16 non-progressive patients had a proliferative but low response . Normal unfractionated tonsillar B cells responded to SAC and BCGF, w hereas normal high buoyant density B cells were unresponsive. After 3 days of stimulation, responding B-CLL cells had multiplied and the B c ells expressed CD5, CD19, and weakly CD21. No cells in the responding cultures exhibited CD3 or the EBV nuclear antigen EBNA-1. Cell maturat ion, measured as IgM secretion, was found in some, but not in all resp onding B-CLL cultures. Thus, B-CLL cells from patients with progressiv e disease have the capacity to respond to signaling through surface lg receptors and to certain T-cell factors which was not the case for B- CLL cells from non-progressive patients. The pattern of in vitro respo nse may be related to disease progression, reflecting a dependency of normal immunoregulatory mechanisms and/or a dysregulation of the growt h control in the leukemic cells.