Identification for human TCRgamma/delta‐recognized epitopes/proteins via CDR3delta peptide‐based immuno‐biochemical strategy

To identify antigenic epitopes/proteins recognized by TCR gamma/delta, we established a new immuno‐biochemical strategy, which is mainly based on binding activity of complementarity determining region 3 in TCR delta (CDR3delta). CDR3delta peptides were firstly synthesized. After validations for their binding specificity to target cells/tissues, the CDR3¦Ä peptides were employed as probes to pan putative epitopes in a 12‐mer random peptide phage‐displayed library, or to identify putative protein ligands within ovarian tumor protein extracts by CDR3¦Ä peptide‐mediated affinity chromatography and the analysis of LC ESI‐MS/MS. We identified nine peptides and two proteins for TCR gamma/delta, including human mutS homolog 2 (hMSH2) and heat shock protein 60. All nine tested epitope peptides could not only bind to gamma/deltaT cells, but also functionally activate gamma/deltaT cells in vitro. The hMSH2 on ovarian tumor cells was recognized by Vdelta2 T cells, suggesting that hMSH2 might be a new protein ligand for TCRdelta. Taken together, our findings provide a novel and facilitative immuno‐biochemical technical strategy to find epitopes/proteins recognized by gamma/deltaT cells.