Interferon α/β mediates early virus-induced expression of H-2D and H- 2K in the central nervous system

Cells of the central nervous system (CNS) normally do not express detectable levels of major histocompatibility complex (MHC) Class I antigens. However, MHC Class I expression can be induced after virus infection. We tested the hypothesis that virus-induced Class I expression is mediated by lymphocytes or cytokines using lymphocyte- and cytokine-deficient mice. We used Theiler's murine encephalomyelitis virus (TMEV), which induces CNS demyelination that maps genetically to the D region of MHC Class I and is associated with high levels of Class I products. TMEV infection of severe combined immunodeficiency (SCID) and recombination activation gene-1- deficient mice, which lack B and T lymphocytes, resulted in equivalent H-2D and H-2K expression in brain and spinal cord, according to analysis of the area and intensity of immunoperoxidase staining. Class I antigens were demonstrated as early as 6 hours after infection, and they were more widely distributed than vital RNA, indicating that expression was induced indirectly via a soluble factor. To determine whether cytokines induced the expression, we infected mice lacking receptors for interferon-α/β (IFN-α/βR(-/-)), interferon-γ (IFN-γR(-/-)), and tumor necrosis factor-α (TNFRp55(-/-)). TMEV-infected IFN-γR(-/-) and TN-FRp55(-/-) mice expressed Class I antigens in the CNS, whereas IFN-α/βR(-/-) mice did not, establishing that IFN- α/β mediated the expression. In contrast to the equivalent expression in SCID mice, we observed greater area and higher intensity of H-2D versus H-2K antigens in infected SCID mice reconstituted with normal spleen cells. Collectively, the data indicate that after TMEV infection, early generalized MHC Class I expression is mediated by IFN-α/β independently of lymphocytes, but the differential regulation of H-2D over H-2K may be controlled by B and/or T lymphocytes.