Enhanced proliferation and IL-1 production of mouse splenocytes by low-dose whole-body X-irradiation.

To elucidate the stimulative effect of low-dose whole-body X-irradiation on the immune system, in vivo, we studied its effects on some immune functions of mouse splenocytes. Results show that Concanavalin A (Con A) and phytohemagglutinin (PHA) responses of splenocytes were significantly increased by irradiation of 2.5 cGy and 5 cGy, whereas lipopolysaccharide (LPS) response was significantly depressed by irradiation of 5 cGy. By irradiation of 2.5 cGy, Con A response was significantly accelerated at each concentration of Con A, but the optimum concentration of Con A shifted to a higher value of 4 micrograms/ml from 2 micrograms/ml in the control group. When blood plasma obtained from 2.5 cGy irradiated mice was added into the medium at 0.005-1%, the Con A response of splenocytes in another un-irradiated mouse was significantly accelerated over that where the plasma added came from the sham-irradiated control mice. Furthermore, 2.5 cGy whole-body irradiation also enhanced the biological activity of intracellular interleukin-1 (IL-1) of LPS-stimulated splenocytes.