| Research Abstract |
While the recognition of peptide antigens by T cells via the TCR has exquisite specificity, many studies have shown flexibility in such recognition. Even certain peptides minimally homologous with a wild-type peptide, exhibit stronger proliferation-inducing activity than did a wild-type on relevant T cells, thereby designated peptide superagonists. We synthesized a set of X9 combinatorial peptide libraries with flanking residues of the core sequence recognized by a K-ras-reactive CD4+ T cell clone. Based on the results for each position of the antigenic peptide, we synthesized several artificial peptides and tested their potential to induce proliferation of the T cell clone. Unexpectedly, none of such peptides induced stronger proliferative responses than did the wild-type. We then used mass spectrometry to overcome drawbacks, and we identified two peptide species that exhibit markedly potent stimulation, as compared with the wild-type.
T cells of unknown specificity are not readily cloned nor are they expanded in sufficient numbers, for full-scale analyses. To overcome these drawbacks, we synthesized Xn (n=9-19) peptides consisting of 9 to 19 residues with random sequences, and found that X19 is effective for the propagation of single CD4T cells, when IL-4, IL-7, IL-9, IL-15 and agonistic Ab to CD29 were included in the culture. Use of combinatorial peptide libraries and pattern-match search on a T cell clone resulted in peptide ligand candidates, one of which induced proliferation, as did protein molecules carrying the corresponding sequence. These strategies combined will contribute to the identification of mimicry peptides, for T cells in autoimmunity.
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