Individual T-Cell Receptors of γ9δ2T-Cells Mediate Differential Anti-Tumor-reactivity

Abstract 4312

Immunotherapy with innate immune cells has recently evoked a broad interest as a novel treatment option for cancer patients. γ9δ2T-cells are an emerging innate cell population with strong anti-tumor-reactivity and a promising candidate for immune interventions. However, the molecular basis of recognition remains unclear as well as whether individual γ9δ2 clones have an advantage as compared to the bulk population in terms of anti-tumor-reactivity. Therefore, bulk γ9δ2T-cells were cloned and tested for reactivity against a broad panel of tumor cells. Between different clones a high variability in recognition pattern was observed in terms of specificity and functional avidity. A number of clones were more potent in tumor recognition while others were weaker than the original bulk population. Thus, we intent to elucidate the molecular basis of observed differences among anti-tumor-reactive clones. The contribution of NK-receptors to γδT-cell activation was verified but could not fully explain their reactive abilities. Therefore, we hypothesized that the diversity within the γ9δ2T-cell receptor (TCR) itself contributes to the differential activity of examined γ9δ2T-cell clones. Hence, clone derived γ9δ2TCRs were expressed in Jurkat- and peripheral blood T cells and indeed: individual γ9δ2TCRs mediated a distinct specificity and functional avidity. By exchanging δ-chains among TCR-transduced T-cell clones with constant γ-chain we demonstrate that distinct δ-chains mediate different functional avidity. Sequence alignments revealed that this phenomenon is selectively caused by differences in the δCDR3 region. Accordingly, alanine-scanning-mutations within δCDR3 were performed. Structurally important residues were identified as well as residues involved in regulating functional avidity, suggesting their importance in antigen-recognition.