Enhancement of concanavalin A-induced proliferation of spleno-lymphocytes by low-dose-irradiated macrophages.

The effect of whole-body irradiation with low doses of gamma-rays was investigated for the Con A-induced proliferation of splenocytes. Proliferation was enhanced by 0.02 Gy irradiation, but was inhibited by 0.2 Gy. The enhanced proliferation produced by low-dose irradiation also was studied using co-cultures of spleno-lymphocytes and peritoneal macrophages (M phi s) instead of spleno-M phi s. The proliferative response of spleno-lymphocytes was not affected by low doses of gamma-ray irradiation; whereas, the responses of unirradiated spleno-lymphocytes cultured with the peritoneal M phi s that had been irradiated at 0.02 and 0.04 Gy respectively were about 120 and 145% of the control. Proliferative enhancement was found when peritoneal M phi s collected 4 h after whole-body irradiation were used, but not with those collected at 1 and 12 h. No enhancement took place when in vitro irradiation was used. These results suggest that the enhancement in Con A-induced proliferation of splenocytes by low-dose irradiation was caused not by the activation of spleno-lymphocytes, but by activation of spleno-M phi s, and that the M phi s were activated indirectly.