Moreover, Tregs were discovered as a group of cells with self‐protective roles in suppressing the attack on autoantigens, through experiments in which T cells from the spleens of mice were transplanted into nude mice; the removal of CD25+ cells from CD25+/CD4+ T cells prior to transplantation resulted in the development of various autoimmune diseases, whereas the transplantation of CD25+/CD4+ T cells suppressed the development of autoimmune diseases (Sakaguchi et al., 1995). This evidence concerns the gene CD4 and autoimmune disease.