The Effects of X-rays on the Responses of Porcine Lymphocytes to the Mitogenic Stimulus of Concanavalin A in Vitro

Summary The proliferative response of porcine lymphocytes in vitro has been studied after X-irradiation at various times before stimulation with concanavalin A (con A). The percentage of cells able to enter DNA synthesis was reduced as the radiation dose and/or the time between irradiation and stimulation was increased. The degree of impairment of response was independent of the con A dose used for stimulation, and the binding of con A to lymphocytes was not significantly altered by irradiation. The magnitude of the loss of the response could be reduced by incubating the irradiated lymphocytes at 4° instead of 37° before stimulation. Fractionated radiation-dose experiments indicated that unstimulated lymphocytes are unable to repair potentially lethal damage between irradiations, as judged by their subsequent ability to enter DNA synthesis. Repair of radiation damage, if it occurs, is probably initiated after activation.