Innate immune system thymus

The effect of low-dose irradiation of the immune system was investigated in mice (Ren et al, 2006). When a 0.2 Gy (20 rad) dose of x-irradiation was administered every other day for a total of four times, the number of lymphocytes yielded by the liver, spleen, and thymus decreased by 10 days, but increased above the level of the control mice by day 28. The population of NK cells dramatically expanded, especially in the liver where primordial lymphocytes were present. Functional and phenotypic activation of these cells occurred at the recovery stage, raising the possibility that an initial activation of macrophages by low-dose irradiation mediated the innate immune system (Ren et al., 2006). 

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