Objective\ To explore the characteristics of intestinal mucosal immunity after gamma irradiation. Methods The number, proliferation activity, cytotoxic activity of small intestinal intraepithelial lymphocytes (IELs),and the TNF α and TGF β concentrations in supernatant of cultured IELs were studied using IELs freshly isolated from whole small intestine of Kunming strain mice after 3,8 and 12 Gy total body 60 Co γ irradiation. Results (1)The number of IELs in small intestinal mucosa of all irradiated mice significantly decreased at 8h,reaching the lowest level at 48 72h post irradiation,then began to rise,but it still did not return to its normal level on day 15.(2)The proliferation activity and cytotoxic activity of IELs isolated from irradiated mice were reduced sharply.They followed the same pattern of decreasing at 8h,reaching the lowest level at 48 72h post irradiation,then began to rise,but it did not return to their normal levels on day 15.(3)The TNF α and TGF β concentrations in supernatant of cultured IELs isolated from irradiated mice were elevated at 8h,reaching their peak at 48 72h. Conclusion The decrease in number and important functions of IELs is one of the factors damaging the intestinal mucosal immunity barrier after total body irradiation.