Role of CD4+CD25+ immunoregulatory T cells in the induction of autoimmune gastritis

A number of experimental models of organ-specific autoimmunity involve a period of peripheral lymphopenia prior to disease onset. There is now considerable evidence that the development of autoimmune disease in these models is due to the absence of CD4(+)CD25(+) regulatory T cells. However, the role of CD4(+)CD25(+) regulatory T cells in the prevention of autoimmune disease in normal individuals has not been defined. Here we have assessed the affect of depletion of CD4(+)CD25(+) regulatory T cells in BALB/c mice on the induction of autoimmune gastritis. The CD4(+)CD25(+) T cell population was reduced to 95% of the original population in adult thymectomized mice by treatment with anti-CD25 mAb. By 48 days after the anti-CD25 treatment, the CD4(+)CD25(+) regulatory T cell population had returned to a normal level. Treatment of thymectomized adult mice for up to 4 weeks with anti-CD25 mAb did not result in the development of autoimmune gastritis. Furthermore, we have demonstrated that depletion of CD4(+)CD25(+) regulatory T cells, together with transient CD4(+) T lymphopenia, also did not result in the development of autoimmune gastritis, indicating that peripheral expansion of the CD4(+) T cell population, per se, does not result in autoimmunity in adult mice. On the other hand, depletion of CD4(+)CD25(+) T cells in 10-day-old euthymic mice resulted in a 30% incidence of autoimmune gastritis. These data suggest that CD4(+)CD25(+) regulatory T cells may be important in protection against autoimmunity while the immune system is being established in young animals, but subsequently other factors are required to initiate autoimmunity.