T cell lines specific for an immunodominant epitope of human basic protein define an encephalitogenic determinant for experimental autoimmune encephalomyelitis-resistant LOU/M rats

The LOU/M rat (RT-1^w) haplotype, although resistant to an encephalitogenic challenge of guinea pig myelin basic protein (Gp-BP)/CFA and unresponsive to Gp-BP, responded strongly to human (Hu)-BP. Both T cell and antibody responses focused on the 110-129 determinant of Hu-BP, and T cells specific for this epitope transferred clinical and histologic experimental autoimmune encephalomyelitis (EAE) to naive LOU/M rats. Moreover, EAE could be induced actively with Hu-BP and a synthetic Hu-S110-129 peptide in CFA, but only with co-immunomodulation by pertussis toxin or cyclophosphamide. Analysis of TCR V region genes revealed the predominant use of the Vβ8.5-Jβ2.3 gene combination, with extensive N region additions to both Dβ1 and Dβ2. These results define the Hu-BP 110-129 peptide sequence as the major encephalitogenic epitope for the LOU/M strain of rat previously considered resistant to EAE, and support the idea that the encephalitogenic property of BP and other CNS Ag for a given MHC is encompassed within immunodominant T cell epitopes. Furthermore, the TCR sequence data indicate the predominant use of a different Vβ8 subfamily member (Vβ8.5) than the Vβ8.2 gene used preferentially by several other rat strains and the PL/J mouse in the T cell response to BP.