Clonotypic heterogeneity of lewis rat T cells specific for the encephalitogenic 68–86 region of myelin basic protein

Abstract

Experimental autoimmune encephalomyelitis was induced in a Lewis rat by sensitization with synthetic peptide GP68-86, representing the 68–86 sequence of guinea pig myelin basic protein (GPMBP). To delineate T cell determinants of GP68-86, lymph node cells from this rat were activated in culture with GP68-86 and were fused with cells of the mouse thymoma BW5147. The resultant hybrids were cloned by limiting dilution and screened for GP68-86-evoked secretion of IL 2 in the presence of rat splenocytes. Twelve T cell hybrids derived in this manner were tested for reactivity to different heterologous species of MBP as well as to substituted or truncated analogs of GP68-86. The hybrids generally exhibited potent reactivity to GPMBP but differed markedly in their reactivity to autologous rat MBP (RMBP). A few exceptional hybrids exhibited crossreactivity with peptides in which native serine 75 or serine 80 residues of GPMBP were substituted with either alanine 75 (A 75) or proline 80 (P 80) residues. These cross-reactive hybrids also possessed high levels of anti-RMBP reactivity. The remaining hybrids were unresponsive to the A 75 and P 80 substituted peptides and, with one exception, had relatively low levels of anti-RMBP reactivity. Unique reactivity patterns were also revealed by hybrid responses to peptides having modified C-terminal 84–86 residues. In summary, the contrasting fine specificities of different hybrids indicated that several distinct clones of T cells mediate the immune response of Lewis rats against the 68–86 region of GPMBP. Furthermore, heterogeneity in the hybrid response to “self” RMBP may reflect substantial differences in encephalitogenic potency of the T cell clones from which these hybrids were derived.