Runx3 drives a tissue residency program that is absent in CD4+ T cells [ATAC-seq]

Tissue-resident memory T (TRM) cells provide rapid and superior control of localized infections. The transcription factor Runx3 was recently identified as a master regulator of CD8+ T cell tissue residency. However, Runx3 also drives CD8+ T cell lineage commitment and is repressed in CD4+ T cells, raising the possibility that this transcription factor defines a form of tissue residency unique to the CD8+ T cell subset. Here, we show that as a direct consequence of Runx3-deficiency, CD4+ TRM cells in epithelia lack the TGFb-responsive transcriptional network that underpins CD8+ TRM cell residency. Ectopic Runx3 expression in CD4+ T cells rescued this transcriptional program to promote prolonged survival, decreased tissue egress and a microanatomical redistribution towards epithelial layers that combined, resulted in superior local immune protection. Our results thus reveal a mechanistic discordance between CD4+ and CD8+ TRM cell formation in barrier tissues that is controlled by Runx3. Consequently, CD4+ TRM cells are unable to adopt a type of tissue residency that is intrinsically accessible to the CD8+ TRM cell subset. Bulk ATAC-seq was performed on mouse CD4 and CD8 T cells with and without Runx3 over expression and with or without TGFB Expression