[Radioresistant CD4+ T cells in normal, unprimed mice: with verification of the Bergonie-Tribondeau law]

This is the first report on radioresistant CD4+ T cells found in normal, unprimed mice. After sublethal whole body irradiation, regular CD4+ as well as primitive NK1.1 + CD4+ T cells were enriched in the spleen. Since it has been well established that virgin T and B cells are highly radiosensitive, these cells were once assumed to be a unique lymphocyte population for which radiosensitivity does not follow the general law of radiation sensitivity for mammalian cells (Bergonie-Tribondeau law). These cells exhibited higher proliferative response to accessory cells than the non-irradiated control cells in the syngeneic mixed leukocyte reaction (SMLR). This indicated that virgin CD4+ T cells sensitized to, and readily respond to self-MHC class II molecules are radioresistant, and that their radioresistance, as activated cells, is consistent with the Bergonie-Tribondeau law.