Kinetics of phytohemagglutinin stimulated lymphocytes in chronic lymphocytic leukemia

The DNA synthesis pattern and several kinetic parameters of in vitro PHA stimulated normal and CLL lymphocytes were determined. The DNA synthesis peak of CLL lymphocytes occurred 2-3 days later than that of normal lymphocytes. The generation time, estimated by the labeled mitoses method, was found to be 28 hr and 20 hr for CLL and normal lymphocytes respectively. This difference was mainly due to longer S and G1 periods. It was also shown that both CLL and normal lymphocytes divide several times. These data were confirmed by the chromatid labeling pattern and by the halving of the grains and the double labeling techniques. By combining continuous and pulse labeling the growth fraction of CLL lymphocytes was found to be progressively increasing, because of the recruitment of new cells in cycle, from the third day of culture. Therefore the delayed peak of DNA synthesis of CLL lymphocytes was caused by a longer cell cycle and by a longer pre-replicative phase.