Female predominance of extrathymic T cells in mice: statistical analysis

Female predominance of autoimmune diseases is widely known in humans and animals. To elucidate one of the underlying mechanisms, we examined whether sex differences exist at the level of extrathymic T cells in various organs of mice under physiological conditions. This attempt came from previous experimental results showing that estrogen administration to mice activates extrathymic T cells in the liver. Extrathymic T cells expressing TCR (and CD3) of intermediate intensity (i.e., intermediate TCR cells) and a high level of IL-2 receptor beta-chain (IL-2R beta), and thymus-derived T cells expressing TCR of bright intensity (i.e., bright TCR cells) and lacking IL-2R beta, were identified by immunofluorescent tests using mAbs. Three groups of different strains were examined. It was demonstrated that intermediate TCR cells were much more predominant in the liver and some other organs tested of female mice than of male mice, of each strain tested.