A TCR V-ALPHA CDR3-SPECIFIC MOTIF ASSOCIATED WITH LEWIS RAT AUTOIMMUNE ENCEPHALOMYELITIS AND BASIC PROTEIN-SPECIFIC T-CELL CLONES

To investigate TCR V alpha gene expression in the Lewis rat model of e xperimental autoimmune encephalomyelitis, we obtained V alpha chain se quences from two V beta 8.2(+)-encephalitogenic, BP72-89-specific T ce ll clones. Two different V alpha genes, a V alpha 2 gene and a V alpha 23 gene, are utilized, but both were found to contain an asparagine r epeat (Asn(3+)) sequence present in the V alpha CDR3 region. This Asn( 3+) motif is also present in the previously reported sequence of a BP6 8-88-specific hybridoma, 510, which utilizes a different V alpha 2 gen e family member, In further experiments, spinal cord T cells were isol ated at the onset of basic protein (BP)-induced disease and sorted for the OX-40 activation marker, which we have previously used to enrich for specifically activated T cells. Analysis of V alpha expression in the OX-40(+) population revealed the biased use of three V alpha genes , V alpha 1, V alpha 2, and V alpha 23. The Asn(3+) motif was present in the V alpha CDR3 region of V alpha 1, V alpha 2, and V alpha 23 cDN A derived from OX-40(+) spinal cord T cells but found to be generally absent in the OX-40(-) spinal cord population, Since these Asn(3+) mot if-bearing V alpha chain sequences are nearly identical to those utili zed by the BP-specific encephalitogenic clones described, it is likely that these V alpha sequences are derived from disease-associated T ce lls in the spinal cord, Thus, we demonstrate that the Asn(3+) V alpha CDR3 motif is strongly associated with experimental autoimmune encepha lomyelitis in the Lewis rat and propose that it plays a role in TCR re cognition of a specific BP peptide/MHC complex.