Sequential and interwoven requirements for HEB and Id3 in fetal gamma-delta T cell commitment and functional programming

• Published in: The Journal of immunology (1950) Vol. 210; no. 1_Supplement; pp. 220 - 220.01
• Main Authors: Anderson, Michele K, Selvaratnam, Johanna, Rocha, Juliana, Rajan, Vinothkumar, Wang, Helen, Reddy, Emily, Guidos, Cynthia, Zuniga-Pflucker, Juan Carlos
• Format: Journal Article
• Language: English
• Published: 01.05.2023
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.210.Supp.220.01

Abstract Two major developmental steps are necessary for the generation of innate IL-17 producing γδ T cells. First, T cell precursors in the fetal thymus commit to either the αβ or the γδ T cell lineage. This is followed by a second stage of differentiation into subsets that can produce either IL-17 (γδT17) or IFNγ (γδT1) cells. Both developmental events are dependent on TCR signal strength, but how this is interpreted at the molecular level has been unclear. Id3, which antagonizes the activity of HEB transcription factors, is upregulated in proportion to TCR signal strength, providing an important link between TCR signaling and gene expression. We previously found that γδ T cells in mice lacking HEB were impaired in IL-17 production. To better understand the molecular basis of this defect, we conducted single cell RNA-sequencing on fetal thymic γδ T cells. In WT cells, the ratio of HEB to Id3 was highest in populations undergoing γδ T cell commitment, whereas later populations were dominated by Id3. Comparing scRNA-seq datasets from WT and HEB-deficient γδ T cells revealed a profound shift in TCRγ and TCRδ chain expression. This was accompanied by a decrease in key regulators of early γδ T cell development. Id3 expression was also severely decreased. Accordingly, Id3-deficient mice were impaired in their ability to generate γδT17 cells. However, γδ T cells from Id3-deficient mice showed a decrease in second stage γδT17 regulators, rather than the first stage regulators defective in HEB-deficient mice. Therefore, distinct ratios of HEB and Id3 are required during the γδ T cell commitment, and HEB is instrumental in inducing Id3 to enable functional programming of γδT17 cells in the fetal thymus. Supported by grants from CIHR (201610PJT), NSERC (RGPIN-2020-05596) and NIH (1P01AI102853-06)