An alternative pathway of nitric oxide production by rat astrocytes requires specific antigen and T cell contact

In the present study, we observed an alternative pathway in which nitric oxide (NO) production by rat astrocytes requires specific antigen and cell-cell contact. NO production by astrocytes was significantly inhibited by antibodies against CD40L, B7-1 or B7-2. Astrocyte-derived NO inhibited T cell proliferation and induced T cell apoptosis. In contrast, augmented astrocyte proliferation was correlated to the levels of NO production by astrocytes, implicating a role of NO in regulating local immune responses in the central nervous system. These results suggest that T cell-astrocyte interactions may regulate local immune responses via the NO pathway and influence the fate of infiltrating T cells.