Deep Characterization of Human γδ T Cell Subsets Defines Lineage-Specific Traits

Abstract Human γδ T cells represent a small fraction of T cells in peripheral blood (1–10%). They constitute a unique subset of T lymphocytes that recognize non-peptide antigens through MHC-independent presentation. Major γδ T cell subsets, Vδ1 and Vδ2 possess distinct tissue localization, antigen recognition, and effector responses. We hypothesized that Vδ1 and Vδ2 T cells possess differences at the gene, phenotypic, and functional level that distinguish them as distinct lineages. Comparisons between each subset have been limited by challenges in isolating sufficient cell numbers for characterization. Through multiparametric flow cytometry we identified phenotypic signatures that defined memory and tissue homing properties specific for each subset. The immune checkpoint marker TIGIT marked a Vδ1 T cell population enriched for higher cytotoxic marker expression. Using a stringent FACS-based isolation method, we compared cytotoxicity and gene expression profiles of highly purified human Vδ1 and Vδ2 cells. Cytotoxicity assays revealed similar killing capacity of Daudi cells possibly through dissimilar mechanisms. Microarray analysis identified shared and subset-specific genetic programs including lower expression of CD3ζ in Vδ1 T cells. Analysis of transcription factors associated with subset-specific gene profiles implicated NFAT in Vδ1 and AhR in Vδ2 T cells as key regulators of ex vivo gene expression. In confirmatory assays, using TCR-dependent and independent stimuli we show higher sensitivity to calcium-mediated NFAT activity in Vδ1 T cells while Vδ2 T cells may require additional activating stimuli. These findings will facilitate further studies into the specific contributions of Vδ1 and Vδ2 T cells to the immune system. NIH NIAID R01 AI125097