Thymus-derived CD4+ CD25+ T cells suppress the development of murine allergic conjunctivitis

CD4+ CD25+ T cells regulate various kinds of immune-mediated diseases. Here, we sought to clarify whether CD4+ CD25+ T cells also regulate the development of experimental allergic conjunctivitis (EC). Thymectomized BALB/c mice, treated with anti-CD25 antibody (PC61), normal rat immunoglobulin G (nrIgG) or left untreated were immunized with short ragweed pollen (RW). Ten days later, the mice were challenged with RW in eye drops, and 24 h later, the conjunctivas, blood and spleens were harvested. The severity of EC, as evaluated by conjunctival eosinophil numbers, was significantly higher in the PC61-treated group as compared with the other two groups. The PC61-treated group also had significantly higher RW-specific IgE and IgG1 levels and displayed RW-specific splenocyte proliferation and RW-induced splenocyte T helper cell 2 cytokine production. However, PC61 treatment of unthymectomized mice did not affect the severity of EC. Thus, thymus-derived CD25+ T cells regulate the development of EC. Furthermore, transfer of Foxp3-expressing CD4+ CD25+ T cells from naïve mice into RW-sensitized mice suppressed the development of EC in these mice after RW challenge. Taken together, these results suggest that CD4+ CD25+ T cells regulate the development of EC.