Joannou, K. | bioRxiv Science

bioRxiv2024

RasGRP1 Signalling Programs Developing γδ-Thymocytes towards the γδT17 Lineage Through Control of c-Maf Expression

The {gamma}{delta} TCR instructively directs both lineage specification and effector programming of developing {gamma}{delta} T cells. However, the manner in which different TCR signal strengths and other auxiliary signals coordinate downstream of the {gamma}{delta} TCR to regulate {gamma}{delta} T cell development remains unclear. In this study we characterized the role of Ras guanyl-releasing protein 1 (RasGRP1) in the development and effector programming of {gamma}{delta} T cells. While RasGRP1 was not necessary for bulk {gamma}{delta} T cell generation, we found it required for efficient generation of V{gamma}4+ thymocytes, and lineage-committed CD73+ {gamma}{delta} T cells in the thymus and periphery. Despite a decrease in immature CD73+ {gamma}{delta} thymocytes, we report an expansion of the perinatal wave of CD8+IFN{gamma}+ {gamma}{delta} T cell population in the absence of RasGRP1. IL-17 producing {gamma}{delta} T cells were significantly reduced in RasGRP1 KO mice, with a specific loss of V{gamma}2+ {gamma}{delta} T cells that corresponds to a loss of c-Maf expression as early as the DN1d thymocyte stage. Critically, these adult-programmed {gamma}{delta}T17s could express c-Maf in response to CCR9 stimulation, with RasGRP1 being required for CCR9-induced c-Maf expression. Thus, RasGRP1 activation serves as an important signalling hub in the effector programming of {gamma}{delta} T cells, which integrates signals from both non-TCR and TCR inputs to direct differentiation.

immunology↗

bioRxiv2021

γδ-Thymocyte Maturation and Emigration

The thymus is the site of both {beta} and {gamma}{delta}-T cell development. After several unique waves of {gamma}{delta}-T cells are generated in, and exported from, the fetal/neonatal thymus, the adult thymus continues to produce a stream of {gamma}{delta}-T cells throughout life. One intriguing feature of {gamma}{delta} T cell development is the coordination of differentiation and acquisition of effector function within the fetal thymus, however, it is less clear whether this paradigm holds true in adult animals. To investigate the relationship between maturation and time since V(D)J recombination in adult-derived {gamma}{delta}-thymocytes, we used the Rag2pGFP model. Immature (CD24+) {gamma}{delta}-thymocytes expressed high levels of GFP while only a small minority of mature (CD24-) {gamma}{delta}-thymocytes were GFP+. Similarly, most GFP+ {gamma}{delta}-splenocytes were immature, while some were mature. Analysis of {gamma}{delta}-recent thymic emigrants (RTEs) indicated that most {gamma}{delta}-T cell RTEs were CD24+ and GFP+ and adoptive transfer experiments showed that immature {gamma}{delta}-thymocytes could be maintained in the periphery for at least 3 days over which time they matured. With respect to the mature {gamma}{delta}-thymocytes that were GFP-, parabiosis experiments demonstrated that mature {gamma}{delta}-T cells did not recirculate from the periphery. Instead, a population of mature {gamma}{delta}-thymocytes remained resident in the thymus for at least 60 days while mature {gamma}{delta}-thymocytes derived solely from adult hematopoiesis were mostly lost from the thymus within 60 days. Collectively, these data demonstrate two streams of actively developing {gamma}{delta}-T cells in adult mice: an immature subset that quickly leaves the thymus and matures in the periphery, and one that completes maturation within the thymus over a longer period of time. Furthermore, there is a fetal-derived and heterogeneous population of resident {gamma}{delta}-thymocytes of unknown functional importance.

immunology↗