Adult thymus-derived cMaf+RORγt+γδ T cells lack Scart2 chromatin accessibility and do not reach periphery

T cell receptor (TCR) Vγ4+expressing γδT cells can be divided into IFN-γ and IL-17-producing effector T cell subsets. A bias towards γδ17 effector fate decisions is observed during early ontogeny. In contrast, the existence of Vγ4+γδ17 cells derived from adult thymus is still controversial. In the present work, we used a mouse model where T cells are exclusive generated within an adult thymus. Additionally, we employed single-cell chromatin state analysis from thymocytes of normal mice. A small, but considerable population of immatureCd24+Gzma+Vγ4 cells was found that exhibit molecular programs of γδ17 cells. These adult thymus-derived immatureCd24a+cMaf+Vγ4 cells secrete small amounts of IL-17A and IL-17F. Interestingly, do not reach the periphery under steady-state conditions. Furthermore,de novogenerated γδ17-like cells from adult thymus lack transcriptional activity of the Scart2 encoding gene, suggesting that Scart2 is a distinct trait of fetal γδT cell precursors. Together, this study provides valuable insights into developmental traits of Vγ4 cells during adulthood and raises the question on signals suppressing the full maturation and/or thymic export of γδ17-like cells within the adult thymus.HighlightsTranscriptional and epigenetic profiling identifies developmental plasticity ofGzma+Cd24a+Vγ4 cells in adult thymus.Thymic c-Maf+and RORγt+Vγ4 T cells can be generated during adulthood, but do not reach the periphery under steady-state conditions.Innate CD44highCD45RBnegγδ17 cells are completely absent upon induction of T cell development during adulthood.Scart2 expression might be a key molecule to track developmental traits of fetal-derived γδ17 cell precursors.