B7-H3 regulates the development of experimental allergic conjunctivitis in mice.

B7-H3 negatively regulates Th1-mediated immune responses. Here, we aimed to investigate whether B7-H3 is involved in the development of murine experimental allergic conjunctivitis (EC), which is predominantly mediated by Th2 cells. Intraperitoneal injection of anti-B7-H3 Ab during the induction phase of EC significantly augmented the severity of EC evaluated as conjunctival eosinophil numbers and Ag-induced IL-5 production by splenocytes. Injection of anti-B7-H3 Ab during the effector phase of EC did not significantly affect the severity of EC. In addition, transfer of Ag-primed splenocytes treated with anti-B7-H3 Ab in vitro did not significantly affect the severity of EC, compared to the splenocytes treated with the control Ab. Thus, regulation of EC by blocking of B7-H3 was observed during the induction phase but not the effector phase. Moreover, this study provides a new notion that B7-H3 regulates not only Th1-mediated but also Th2-mediated immune reactions.