REPERTOIRE OF RAT MBP-REACTIVE T-CELLS - DNA-SEQUENCING ANALYSIS FURTHER DEMONSTRATES THE CLONAL HETEROGENEITY OF RAT T-CELLS REACTIVE AGAINST ENCEPHALITOGENIC EPITOPES

Reports of the expression of very similar TCR structures by disparate rodent encephalitogenic T cells reactive with regions of MBP have arou sed much interest for both theoretical and practical reasons. To ascer tain the extent to which structural requirements of epitope recognitio n constrain TCR expression by MBP-reactive T cells, we set out to esti mate the size of the overall repertoire of TCR beta-chain V beta-D bet a-J beta (VDJ) assemblies in T cells of Lewis rats specific for MBP(68 -88) as well as those specific for MBP(87-99). We previously reported that such T cells can express a diversity of V beta genes as revealed by PCR analysis. In this study, we have used direct sequencing of PCR products amplified from encephalitogenic T-cell clones and pauciclonal T-cell lines to demonstrate that VDJ structures of the rat T cells sp ecific for either residues 68 to 88 or 87 to 99 of MBP are highly hete rogeneous. Our results showed that (1) no pattern is evident in the ut ilization of germline J gene segments by individual T-cell clones; fro m a total of over 100 successfully sequenced clones displaying in-fram e rearrangements, all the J beta segments have been demonstrated. (2) Even among the T-cell clones which share the V beta expression, J beta is variable. (3) Due to joining variations between the V beta, D beta , and J beta gene segments, no two of the T-cell clones examined share entire VDJ structures. Our study is the first report of nucleotide an d amino acid sequences of TCR beta-chains from rat encephalitogenic T cells expressing V beta genes other than V beta 8.2. It demonstrates t hat the TCR repertoire of the MBP-reactive as well as encephalitogenic T cells is heterogeneous, even though a certain T-cell subset frequen tly dominated by the mechanism needs to be clarified. (C) 1994 Academi c Press, Inc.