Interleukin 4 drives phytohemagglutinin-activated T cells through several cell cycles: No synergism between interleukin 2 and interleukin 4

Cell kinetic studies of T cells stimulated with the interleukin 2 (Il-2), Il-4, or both lymphokines were performed with conventional 3H]thymidine incorporation and with the bivariate BrdU/Hoechst technique. Il-2 and Il-4 are able to drive phytohemagglutinin-activated T cells through more than one cell cycle. Neither synergistic nor inhibitory effect on T-cell proliferation was seen for the stimulation with both Il-2 and Il-4 as compared with the effect of Il-2 alone. The quantitative data of the cell cycle distribution of phytohemagglutinin-activated T cells suggest that the population of Il-4-responsive cells is at least an overlapping population, if not a real subset of the population of the Il-2-responsive cells.