MHC Class I-Restricted Myelin Epitopes Are Cross-Presented by Tip-DCs That Promote Determinant Spreading to CD8(+) T Cells

Myelin presentation to T cells within the central nervous system (CNS) sustains inflammation in multiple sclerosis (MS). CD4(+) and CD8(+) T cells contribute to MS; however, only cells that present myelin to CD4(+) T cells have been identified. We show that MHC class I-restricted myelin basic protein (MBP) was presented by oligodendrocytes and cross-presented by Tip-dendritic cells (DCs) during experimental autoimmune encephalomyelitis (EAE), an animal model of MS initiated by CD4(+) T cells. Tip-DCs activated naïve and effector CD8(+) T cells ex vivo, and naïve MBP-specific CD8(+) T cells were activated within the CNS during CD4(+) T cell-induced EAE. These results demonstrate that CD4(+) T cell-mediated CNS autoimmunity leads to determinant spreading to myelin-specific CD8(+) T cells that are capable of direct recognition of oligodendrocytes.