Human lymphocyte cell cycle: studies with the use of BrUdR.

The chronological distributions of human blood lymphocytes in first, second and third mitosis following PHA stimulation in vitro are presented. The first G1 phase is shown to be of variable length resulting in some first mitoses appearing only about 150 h after stimulation. The serum or plasma used in the culture medium influences cell cycle time. A total cell cycle time of 10.6 h was estimated for cultures with autologous donor plasma and of 14.7 h for cultures with fetal calf serum. It was further calculated that following PHA stimulation 90% of the lymphocytes divide once, about 65% divide for a second and about 40% divide for a third time.