Heterogeneity of responsiveness of chronic lymphocytic leukemic B cells to B cell growth factor or interleukin 2

We compared the proliferative responses of purified human leukemic B cells from 12 cases of chronic lymphocytic leukemia to highly purified B cell growth factor (BCGF) and recombinant interleukin 2 (rIL 2) spontaneously, and in a coactivation assay using anti-mu monoclonal antibodies. Heterogeneity of response to one or the other lymphokine was observed from case to case. Spontaneous responses were observed to BCGF in one case, to rIL 2 in 3 cases and to both lymphokines in one other case. Costimulation with anti-mu monoclonal antibody induced a proliferative response to BCGF in 3 additional cases and to rIL 2 in 4 cases. Interestingly, cells from BCGF-responsive cases also proliferated in response to rIL 2. The leukemic B cells from 4 chronic lymphocytic leukemia patients were unresponsive. Cells from 5 cases expressed IL 2 receptors, although rIL 2 induced a direct proliferative response in only 3 of these cases. Expression of the B cell activation antigen B5 was associated to BCGF responsiveness.