Direct link between mhc polymorphism, T cell avidity, and diversity in immune defense

Altered CD8+ T cell responses to selected Epstein-Barr virus immunodominant epitopes in patients with multiple sclerosis

An increased frequency of antiviral CD8+ T cells is seen in chronic viral infections. During herpes virus infections the expanded CD8+ T cells are thought to control the reactivation of the latent infection. Because multiple sclerosis (MS), a presumed autoimmune disease of the central nervous system, has been associated with a late Epstein-Barr virus (EBV) infection, we wished to examine whether the CD8+ T cell response to EBV epitopes differed between MS patients and healthy controls. Here we report an increased frequency of CD8+ T cells responding to EBV epitopes from nuclear antigen 3 A (HLA-A2/CLG) and latent membrane protein 2 (HLA-B7/RPP) in MS patients. Noticeably, the altered CD8+ T cell response occurred to some but not all EBV epitopes and did not reach the high level seen during acute infection. The responses towards two immunodominant epitopes from human cytomegalovirus (HCMV) were similar in MS patients and normal controls. Together, our data demonstrate the presence of an increased frequency of CD8+ T cells reacting with two epitopes from EBV in patients with MS. The altered response to only two of the tested EBV epitopes would be consistent with the presence of cross-reactive epitopes.

Could TCR antagonism explain associations between MHC genes and disease?

Alleles of major histocompatibility complex (MHC) loci are associated with certain types of diseases, including those of infectious and autoimmune origin. MHC products can promote susceptibility or resistance to disease by stimulating or inhibiting immune responses. Recent evidence suggests that MHC-associated peptides derived from self-proteins can act as antagonists of T-cell activation, thereby inhibiting immune responses to antigens. We suggest that self-peptide-promoted antagonism might explain some associations between MHC alleles and particular chronic diseases.