ACTIVATION OF HUMAN LYMPHOCYTES-B .8. DIFFERENTIAL RADIOSENSITIVITY OF SUB-POPULATIONS OF LYMPHOID-CELLS INVOLVED IN POLYCLONALLY-INDUCED PFC RESPONSES OF PERIPHERAL-BLOOD B LYMPHOCYTES

Abstract

The differential effect of various doses of irradiation on subpopulations of human peripheral blood lymphoid cells involved in the pokeweed mitogen (PWM) induced PFC [plaque forming cell] response against sheep red blood cells (SRBC) was studied. The plaque forming B [bone marrow derived] cells were quite sensitive to low doses of irradiation with complete suppression of responses at 300-500 rad. Helper T[thymus derived]-cell function was resistant to 2000 rad. Co-culture of irradiated T cells with autologous or allogeneic B cells resulted in marked enhancement of PFC responses consistent with the suppression of naturally occurring suppressor cells with a resulting pure helper effect. Irradiated T cell-depleted suspensions failed to produce this effect as did heat killed T cells, whereas mitomycin C treated T cells gave effects similar to irradiated T cells. These findings were consistent with a lack of requirement of cell division for a T cell helper effect and a requirement of mitosis or another irradiation sensitive, mitomycin C sensitive process for a T suppressor cell effect. These studies have potential relevance in the evaluation of subpopulations of human lymphoid cells involved in antibody production in normal individuals and in disease states.