A clonotypic Vγ4Jγ1/Vδ5Dδ2Jδ1 innate γδ T-cell population restricted to the CCR6+CD27- subset

Here we investigate the TCR repertoire of mouse V gamma 4(+) gamma delta T cells in correlation with their developmental origin and homeostasis. By deep sequencing we identify a high frequency of straight V delta 5D delta 2J delta 1 germline rearrangements without P- and N-nucleotides within the otherwise highly diverse Trd repertoire of V gamma 4(+) cells. This sequence is infrequent in CCR6(-)CD27(+) cells, but abundant among CCR6(+)CD27(-) gamma delta T cells. Using an inducible Rag1 knock-in mouse model, we show that gamma delta T cells generated in the adult thymus rarely contain this germline-rearranged V delta 5D delta 2J delta 1 sequence, confirming its fetal origin. Single-cell analysis and deep sequencing of the Trg locus reveal a dominant CDR3 junctional motif that completes the TCR repertoire of invariant V gamma 4(+)V delta 5(+) cells. In conclusion, this study identifies an innate subset of fetal thymus-derived gamma delta T cells with an invariant V gamma 4(+)V delta 5(+) TCR that is restricted to the CCR6(+)CD27(-) subset of gamma delta T cells.