The proliferative activity of B-chronic lymphocytic leukaemia lymphocytes prior to and after stimulation with TPA and PHA.

The proliferative activity of B-CLL lymphocytes from 10 patients was investigated both prior to and after stimulation with TPA and PHA. The analysis of cell cycle-associated features such as BrdU incorporation and the expression of the nuclear proliferation-associated antigen, Ki-67, together with the phenotypic profile of the cells, was performed using double colour immunofluorescent methods. The unstimulated B-CLL cells represented a homogeneous population with the same cell cycle position (G0) as resting peripheral blood lymphocytes. After TPA stimulation 22.7% of the lymphocytes were found in G1, 9.4% in S + G2/M and 13.4% in post-M. PHA stimulation induced a greater proportion of cells in G1, i.e. 35% and 17.8% into S + G2/M and 13.4% into post-M. Double colour immunofluorescence was able to demonstrate that in TPA cultures the majority of the stimulated lymphocytes originated from the malignant clone. Evidence of B-CLL lymphocyte proliferation using double colour labelling with BrdU and Ig kappa and/or Ig lambda showed that a small minority of B-CLL lymphocytes were stimulated into S + G2/M phases of the cell cycle. PHA was also capable of inducing a small proportion of B-CLL cells into mitosis although this proportion of cells was smaller compared to the TPA-stimulated lymphocytes.