Effects of low-dose irradiation on enhancement of immunity by dendritic cells

Low-doses of irradiation have been reported to have beneficial effects, particularly anti-tumor effects. In this paper, we show the effects of the low-dose irradiation on T cell activation induced by dendritic cells (D Cs). D Cs, which had been pre-irradiated at 0.02-1.0 Gy from a 137Cs source, were cultured with allogeneic T cells, and the proliferation of T cells was then examined. The 0.05 Gy-pre-irradiated D Cs showed the highest proliferation capacity of T cells. The 0.05 Gy-irradiation does not augment the expression of major histocompatibility complexes (MHC s) or co stimulatory molecules on D Cs, as with non-irradiated D Cs or 1 Gy-irradiated D Cs, but does augment the production of Il-2, Il-12 and interferon (If)-γ D Cs. These results suggest that the low-dose irradiation augments T cell-activation capacity through cytokine production by D Cs, which might shift naive helper T cells to Th1 cells. (author)