Effects of irradiation upon the response of murine spleen cells to mitogens.

The mitogenic response of murine spleen cells exposed to graded doses of radiation was evaluated. Low-dose exposures were associated with an augmented response to concanavalin A (Con A) that was most marked with 100 rads. Low-dose augmentation of phytohemagglutinin (PHA) stimulation was equivocal and most pronounced in cells exposed to 10-20 rads. Augmentation was only demonstrable when the cells were irradiated immediately prior to mitogenic stimulation. Timed exposures after stimulation with Con A or PHA showed no evidence that mitogen activation increased radioresistance, although the possibility could not be excluded that activation protects against interphase cell death. Reduced isotope incorporation was associated with all doses of radiation evaluated in cells stimulated with lipopolysaccharide (LPS) or pokeweed mitogen (PWM). On this basis it is concluded that 1) each of the mitogens tested differs in its capacity to stimulate irradiated spleen cells; 2) radiation-induced augmentation is noted with those mitogens (Con A and possibly PHA) known to activate only T cells; 3) radiation-induced augmentation may be due to the release of mitogenically active molecules by injured lymphocytes.