The role of CD8+ T cells is less clear though several observations suggest their involvement in MS such as high abundance in MS lesions, low or transient expression of HLA class I molecules on the surface of microglia, oligodendrocytes and neurons (53, 54), and observations that EAE does not develop in B2-microglobulin knockout mice (55). This evidence concerns the gene CD8A and myeloid sarcoma.