Regulation of gamma delta (γδ) T cell effector programming by the SLAM/SAP signaling pathway 2310142

Introduction Gamma delta (γδ) T cells are innate-like T cells that shape the developing adaptive immune response through their ability to rapidly produce large amounts of cytokines such as IL-17 (γδT17) and IFN-γ (γδT1). Unlike conventional αβ T cells, γδ T cells acquire their effector function during thymic development through mechanisms that remain unclear. Previously, we reported that the SLAM/SAP signaling pathway regulates both thymic γδT17 and γδT1 development. Here, we investigated whether the SLAM/SAP signaling pathway regulates thymic γδ T cell developmental programming through its ability to modulate TCR signal strength. Methods Using a novel B6.Nur77GFP.SAP-/- reporter strain, we used multi-parameter flow cytometric analysis to compare the expression of canonical markers of γδ TCR signaling, Nur77 transcription and CD5 protein expression, between B6 and B6.SAP-/- mice during embryonic and adult thymic developmental stages. Results Ex vivo analysis of embryonic day 17 thymic γδ T cells revealed both decreased CD5 expression and increased Nur77-GFP expression in B6.Nur77GFP.SAP-/- γδ T cells. Re-analysis of our previously published E.17 scRNAseq dataset revealed enrichment of Nr4a1 in the γδT1 subsets and enrichment of Cd5 in the γδT17 subsets. In vitro co-stimulation of thymic B6.Nur77GFP γδ T cells with anti-TCRδ and anti-SLAMF antibodies revealed increased Nur77-GFP compared to anti-TCRδ alone. Further in vitro stimulations of B6.Nur77GFP and B6.Nur77GFP.SAP-/- thymocytes with anti-TCRδ revealed increased GFP expression in B6.Nur77GFP.SAP-/- γδ T cells. Conclusion All together, these data suggest that the SLAM/SAP signaling pathway can modulate the TCR signal strength of thymic γδ T cells. However, it may utilize fundamentally different modes of action in cells destined for the γδT17 and γδT1 effector fate, where SAP is co-stimulatory during γδT17 development, but is inhibitory during γδT1 development.