In vivo expression of major histocompatibility complex molecules on oligodendrocytes and neurons during viral infection

Demyelination hi multiple sclerosis and in animal models is associated with infiltrating CD8+ and CD4+ T cells. Although oligodendrocytes. and axons a re damaged in these diseases, the roles T cells play in the demyelination p rocess are not completely understood. Antigen-specific CD8+ T cell lysis of target cells is dependent on interactions between the T cell receptor and major histocompatibility complex (MHC) class I-peptide complexes on the tar get cell. In the normal central nervous system, expression of MHC molecules is very low but often increases during inflammation. We set out to precise ly define which central nervous system cells express MHC molecules in vivo during infection with a strain of murine hepatitis virus that causes a chro nic, inflammatory demyelinating disease. Using double immunofluorescence la beling, we show that during acute infection with murine hepatitis virus, MH C class I is expressed in Vivo by oligodendrocytes, neurons, microglia, and endothelia, and MHC class H is expressed only by microglia. These data ind icate that oligodendrocytes. and neurons have the potential to present anti gen to T cells and thus be damaged by direct antigen-specific interactions with CD8+ T lymphocytes.