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Summary: T helper (Th)17 cells mediate both protective anti-bacterial immune responses and autoimmune pathogenesis, but the distinct pathways regulating these Th17 responses remain unclear. Retinoid-related orphan receptor γ t (RORγt) is a master transcription factor that governs Th17 cell generation and effector functions. We found that a K256R mutation in RORγt impairs Th17-mediated experimental autoimmune encephalomyelitis (EAE) without affecting the clearance of Citrobacter rodentium. This indicates distinct RORγt roles in central nervous system pathogenesis versus gut-associated protective Th17 responses. Mechanically, RORγt/Runx1-dependent upregulation of galectin-3 (Lgals3) and chemokine receptor Ccr6 in CD4+ T cells is essential for EAE development but not for bacterial clearance. Moreover, Lgals3 is selectively required for recruiting macrophages to produce interleukin (IL)-1β, which in turn promotes Ccr6 expression on CD4+ T cells during EAE pathogenesis. Our findings highlight different RORγt-regulated Th17 pathways in autoimmunity and anti-bacterial immunity, with implications for therapies targeting Th17-mediated autoimmunity while preserving effective anti-bacterial responses.

Summary: Canonical NF-κB signaling is constitutively activated in acute myeloid leukemia (AML) stem cells and is required for maintenance of the self-renewal of leukemia stem cells (LSCs). However, any potential role for NF-κB non-canonical signaling in AML has been largely overlooked. Here, we report that stabilization of NF-κB-inducing kinase (NIK) suppresses AML. Mechanistically, stabilization of NIK activates NF-κB non-canonical signaling and represses NF-κB canonical signaling. In addition, stabilization of NIK-induced activation of NF-κB non-canonical signaling upregulates Dnmt3a and downregulates Mef2c, which suppresses and promotes AML development, respectively. Importantly, by querying the connectivity MAP using up- and downregulated genes that are present exclusively in NIK-stabilized LSCs, we discovered that verteporfin has anti-AML effects, suggesting that repurposing verteporfin to target myeloid leukemia is worth testing clinically. Our data provide a scientific rationale for developing small molecules to stabilize NIK specifically in myeloid leukemias as an attractive therapeutic option. : Xiu et al. identify a myeloid-leukemia-suppressive role of NIK, which is different from NIK’s tumor-promoting role in lymphoid neoplasms. They show that stabilization of NIK activates non-canonical but represses canonical NF-κB signaling, indicating that NF-κB non-canonical signaling has a role opposite to that of canonical signaling in AML. Keywords: NF-κB, NIK, RelB, RelA, DNMT3A, MEF2C, MLL-AF9, AML, leukemia stem cells, LSCs

Summary: CD4+ Foxp3+ T regulatory (Treg) cells are key players in preventing lethal autoimmunity. Tregs undertake differentiation processes and acquire diverse functional properties. However, how Treg’s differentiation and functional specification are regulated remains incompletely understood. Here, we report that gradient expression of TCF1 and LEF1 distinguishes Tregs into three distinct subpopulations, particularly highlighting a subset of activated Treg (aTreg) cells. Treg-specific ablation of TCF1 and LEF1 renders the mice susceptible to systemic autoimmunity. TCF1 and LEF1 are dispensable for Treg’s suppressive capacity but essential for maintaining a normal aTreg pool and promoting Treg’s competitive survival. As a consequence, the development of T follicular regulatory (Tfr) cells, which are a subset of aTreg, is abolished in TCF1/LEF1-conditional knockout mice, leading to unrestrained T follicular helper (Tfh) and germinal center B cell responses. Thus, TCF1 and LEF1 act redundantly to control the maintenance and functional specification of Treg subsets to prevent autoimmunity. : Transcriptional regulation of Treg differentiation and function remains incompletely understood. Yang et al. report that two TCF family transcription factors regulate the survival and functional specification of a subset of Treg cells to prevent autoimmunity. Keywords: regulatory T cells, TCF1, LEF1, autoimmunity, Tfr, homeostasis, competitive fitness

Selected CD8+ T cells must divide, produce differentiated effector cells, and self-renew, often repeatedly. We now show that silencing expression of the transcription factor TCF1 marks loss of self-renewal by determined effector cells and that this requires cell division. In acute infections, the first three CD8+ T cell divisions produce daughter cells with unequal proliferative signaling but uniform maintenance of TCF1 expression. The more quiescent initial daughter cells resemble canonical central memory cells. The more proliferative, effector-prone cells from initial divisions can subsequently undergo division-dependent production of a TCF1-negative effector daughter cell along with a self-renewing TCF1-positive daughter cell, the latter also contributing to the memory cell pool upon resolution of infection. Self-renewal in the face of effector cell determination may promote clonal amplification and memory cell formation in acute infections, sustain effector regeneration during persistent subclinical infections, and be rate limiting, but remediable, in chronic active infections and cancer.