Evolving view of the in-vivo kinetics of chronic lymphocytic leukemia B cells.

B-cell chronic lymphocytic leukemia (B-CLL) has long been considered a disease of "accumulation," due to a presumed defect in programmed cell death. Recent data, however, suggest that B-CLL cells are born at a normal to an accelerated rate, with the rate of proliferation varying among patients. In addition, differences in birth rates, activation state, and inducibility appear to exist among subpopulations of cells within individual leukemic clones. The extent to which such dissimilarities influence clinical course and outcome is still unclear. This review examines the evidence supporting the existence of a proliferative compartment in B-CLL and the role that proliferating cells might play in the progression and evolution of this disease.