Interleukin (IL)-10 is known to be a multifunctional cytokine. This study was designed to evaluate the role of IL-10 during respiratory syncytial virus (RSV) infection using a C57BL/6 transgenic (TG) mouse model in which the expression of murine IL-10 cDNA was regulated by a human salivary amylase promoter (IL-10 TG mice). These mice expressed a large amount of IL-10 in the nasal mucosa and in salivary glands. Viral replication in the respiratory tract after intranasal infection with RSV was suppressed significantly in IL-10 TG mice compared to non-transgenic controls. This suppression was IL-10 specific, because it was prevented by treating mice with neutralizing anti-IL-10 antibodies. We also found that IL-10-stimulated T cells displayed cytotoxic activity against infected murine nasal epithelial cells. Previous data indicated that IL-10 induces Fas ligand (L) expression on mouse T cells. Taken together, these data suggest that Fas/Fas L mediated cytotoxicity is involved in the suppression of RSV replication observed in IL-10 TG mice after intranasal infection.
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