Response of human lymphocytes to mitogenic stimuli after irradiation in vitro

Human lymphocytes were exposed to varying doses of roentgen irradiation in vitro and thereafter tested for reactivity to different polyclonal mitogens and antigens using DNA synthesis as a marker for viability. The dose response profiles obtained indicate that there are two subpopulations of lymphocytes which are responsive to phytohaemagglutinin, poke weed mitogen, concanavalin A and allogeneic cells. One is relatively sensitive to radiation and the other is relatively resistant. However, no "resistant" PPD-tuberculin responsive cell population could be detected. Irradiated lymphocyte populations enriched for T-cells exhibited both a sensitive and a resistant PHA-responsive population, whereas cell populations enriched for B-cells only exhibited a radiation sensitive one.