A clonotypic V g 4 J g 1 / V d 5 D d 2 J d 1 innate gd T-cell population restricted to the CCR 6 þ CD 27 subset

Here we investigate the TCR repertoire of mouse Vg4þ gd T cells in correlation with their developmental origin and homeostasis. By deep sequencing we identify a high frequency of straight Vd5Dd2Jd1 germline rearrangements without Pand N-nucleotides within the otherwise highly diverse Trd repertoire of Vg4þ cells. This sequence is infrequent in CCR6 CD27þ cells, but abundant among CCR6þCD27 gd T cells. Using an inducible Rag1 knock-in mouse model, we show that gd T cells generated in the adult thymus rarely contain this germline-rearranged Vd5Dd2Jd1 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 Vg4þVd5þ cells. In conclusion, this study identifies an innate subset of fetal thymus-derived gd T cells with an invariant Vg4þVd5þ TCR that is restricted to the CCR6þCD27 subset of gd T cells. DOI: 10.1038/ncomms7477