ENHANCED MITOGEN-INDUCED PROLIFERATION OF RAT SPLENOCYTES BY LOW-DOSEWHOLE-BODY X-IRRADIATION

To elucidate the stimulative effect on the immune system, we studied t he effect of acute low-dose whole-body X-irradiation on the mitogen-in duced proliferative responses of rat splenocytes and thymocytes. Conca navalin A (Con A)-induced mitogen response of rat splenocytes 4 hours after 5 cGy irradiation was significantly higher (by 80%, p < 0.02) th an that in sham-irradiated controls; whereas that of rat thymocytes di d not show change after irradiation of 1-10 cGy. In the rats X-irradia ted with doses greater than 25 cGy, Con A-induced mitogen responses of splenocytes and thymocytes were reduced. In a way similar to the Con A-induced mitogen response of splenocytes, the mitogen response of spl enocytes induced by phytohemagglutinin (PHA) or lipopolysaccharide (LP S) was significantly increased by X-irradiation with 5 cGy (by 50%, p < 0.02). The enhancement of mitogen response of splenocytes was observ ed within a few hours after irradiation, being a temporary effect. Aft er 5 cGy irradiation the level of leukotriene Bq (LTB(4)) in the super natant fraction of the splenocyte suspension showed a significant incr ease (by 40%, p < 0.05).