Single-cell analysis of γδ T cells reveals limited TCR delta chain diversity in mouse lung Vγ4 γδ T cells

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Abstract γδ T cells are innate-like T cells that are one of the first responders in the defense against pathogens through their rapid production of pro-inflammatory cytokines like IL-17 and IFN-γ. Currently, the mechanisms that direct γδ T cells to exert these distinct effector functions are unknown. The limited TCR diversity of tissue-specific γδ T cells is often associated with specific effector functions. We have recently found that IL-17- and IFN-γ-producing Vγ4 γδ T cells in the lung are marked by SLAM1 and SLAM6 cell surface receptors, respectively. Our long-term goal is to investigate the link between γδ T cell effector function, specific SLAM family receptor expression, and TCR clonotype usage. The objective of this study was to identify the major Vγ4 γδ TCR clonotype(s) in the mouse lung. Vγ4 γδ T cells were single cell-sorted and paired TCR clonotypes were identified using next-generation sequencing of TCR amplicon libraries. Out of 789 sorted lung C57BL/6 Vγ4 T cells, we obtained paired TCR γ and δ chain sequences from 396 cells. These data revealed that Vδ5 and Vδ2 chains accounted for 56.20% and 35.77% of the productive TCRδ chain rearrangements, respectively. A significant fraction of the Vδ5 sequences were characterized by invariant germline-encoded (28.57%) or highly restricted (9.10%) Vδ5Dδ2Jδ1 sequences. Likewise, 55.10% of the Vδ2 sequences were characterized by a highly restricted Vδ2Dδ2Jδ1 sequence. These data reveal that the lung Vγ4 γδ T cell population is characterized by extremely limited delta chain usage. Since lung Vγ4 T γδ cells are programmed to be SLAM1+IL-17+ or SLAM6+IFN-γ+, future studies will determine whether there is a link between this limited TCRδ chain usage, cytokine production, and SLAM receptor expression.