Abstract
Forkhead box protein 3-expressing (FOXP3(+)) regulatory T cells (T(reg) cells) suppress conventional T cells and are essential for immunological tolerance. FOXP3, the master transcription factor of T(reg) cells, controls the expression of multiples genes to guide T(reg) cell differentiation and function. However, only a small fraction (<10%) of T(reg) cell-associated genes are directly bound by FOXP3, and FOXP3 alone is insufficient to fully specify the T(reg) cell programme, indicating a role for other accessory transcription factors operating upstream, downstream and/or concurrently with FOXP3 to direct T(reg) cell specification and specialized functions. Indeed, the heterogeneity of T(reg) cells can be at least partially attributed to differential expression of transcription factors that fine-tune their trafficking, survival and functional properties, some of which are niche-specific. In this Review, we discuss the emerging roles of accessory transcription factors in controlling T(reg) cell identity. We specifically focus on members of the basic helix-loop-helix family (AHR), basic leucine zipper family (BACH2, NFIL3 and BATF), CUT homeobox family (SATB1), zinc-finger domain family (BLIMP1, Ikaros and BCL-11B) and interferon regulatory factor family (IRF4), as well as lineage-defining transcription factors (T-bet, GATA3, RORγt and BCL-6). Understanding the imprinting of T(reg) cell identity and specialized function will be key to unravelling basic mechanisms of autoimmunity and identifying novel targets for drug development.