RESUMO
The immunosuppressive effects of high doses of ionizing radiation have long been known. Recently, in human and experimental animal models it has been reported that low dose radiation may have immunostimulatory effects. The aim of this study was to evaluate the effects of low doses of diagnostic X-ray on cell mediated and humoral immune responses in a Balb/c animal model. In this experimental study, three groups of male Balb/c mice were exposed once, twice and three times to 30 mGy X-ray radiation. Two to 4hrs after the irradiation, the delayed type hypersensitivity [DTH] and humoral responses to sheep red blood cell [SRBC] were measured and compared to the responses of sham and control groups. The mean titer of anti-SRBC antibodies in two-times irradiated [74.66 +/- 26.12] and three-times irradiated [128 +/- 70.1] groups were significantly higher than those of the control [26.66 +/- 8.26] and sham [28.8 +/- 20.86] groups [p<0.001]. However, no significant differences were observed between the mean titer of anti-SRBC antibodies in one-time irradiated [22.4 +/- 8.76] and either control or sham groups. Similarly, comparing DTH responses showed that the differences between either two-times irradiated [12.2 +/- 3.9] or three times-irradiated [6.9 +/- 3.7] and control [4 +/- 0.2] or sham [4.3 +/- 3] groups was statistically significant [p<0.001]. Theses results showed that twice and three-times irradiated mice demonstrated significant stimulatory effects on both DTH and antibody responses. However, one-time irradiated animals did not exhibit any bio-positive effect on DTH and humoral responses. Moreover, no statistically significant difference was observed between the DTH and antibody responses of two-times and three-times irradiated mice