T cells of multiple sclerosis patients target a common environmental peptide that causes encephalitis in mice

Multiple sclerosis (MS) is a chronic autoimmune disease triggered by unknow n environmental factors in genetically susceptible hosts. MS risk was linke d to high rates of cow milk protein (CMP) consumption, reminiscent of a sim ilar association in autoimmune diabetes. A recent rodent study showed that immune responses to the CMP, butyrophilin, can lead to encephalitis through antigenic mimicry with myelin oligodendrocyte glycoprotein. In this study, we show abnormal T cell immunity to several other CMPs in MS patients comp arable to that in diabetics. Limited epitope mapping with the milk protein BSA identified one specific epitope, BSA(193), which was targeted by most M S but not diabetes patients. BSA(193) was encephalitogenic in SJL/J mice su bjected to a standard protocol for the induction of experimental autoimmune encephalitis. These data extend the possible, immunological basis for the association of MS risk, CMP, and CNS autoimmunity. To pinpoint the same pep tide. BSA(193) in encephalitis-prone humans and rodents may imply a common endogenous ligand, targeted through antigenic mimicry.