Journal of Experimental Medicine最新文献

Tumor necrosis factor α (TNFα) maintains homeostasis through promoting cell survival or cell death; however, how this process is regulated by metabolic pathways remains largely unknown. Here, we identify adenosine kinase (ADK), the key enzyme for catalyzing the conversion of adenosine to AMP, as an endogenous suppressor of RIPK1 kinase. ADK-mediated adenosine metabolic clearance is a prerequisite for transmethylation reactions on various cellular targets. We found that ADK licenses constitutive R606 symmetric dimethylation in RIPK1 death domain (DD), which is catalyzed by protein arginine methyltransferase 5. Upon TNFα stimulation, DD-mediated RIPK1 dimerization is inhibited by R606 methylation, preventing RIPK1 kinase activation and keeping cell death in check. Both hepatocyte-specific ADK knockout and systemic ADK inhibition cause spontaneous RIPK1-driven hepatocyte death, which leads to hepatic homeostasis disruption. Furthermore, ADK is reduced in hepatic ischemia-reperfusion, aggravating hepatic injury during liver surgery. Thus, this study reveals a mechanism of adenosine metabolism-dependent homeostasis maintenance that is implicated in both physiological and pathological conditions.

Antigen-specific oral tolerance prevents harmful immune responses in naïve animals but is difficult to induce in antigen-primed hosts. Here, we showed that feeding of antigen-containing diet generated peripherally derived regulatory T (pTreg) cells with tissue-adapted effector properties. They acquired Treg-specific epigenomic changes at Treg signature genes, including Foxp3, exhibiting stable suppressive function. Cessation of antigen feeding diminished pTreg cells, hampering tolerance induction. Notably, pTreg cells induced by antigen feeding predominantly expressed CD101. CD101+ Treg cells with similar phenotypic and epigenetic features could also be generated in vitro from antigen-primed naïve CD4+ T cells by blocking CD28-mediated costimulation during TGF-β-dependent Treg induction. Furthermore, in mice already antigen-sensitized by nonoral routes, in vivo blockade of CD28 signaling with CTLA4-Ig prior to antigen feeding promoted differentiation of antigen-specific T cells into CD101+ pTreg cells, facilitating oral tolerance. Thus, continuous oral antigen exposure combined with CD28 blockade generates functionally stable CD101+ pTreg cells, thereby establishing systemic antigen-specific tolerance even in antigen-presensitized hosts.

Ulcerative colitis (UC) is primarily characterized by inflammation-induced tissue damage, but impaired tissue repair also drives disease progression. This study demonstrates group 2 innate lymphoid cells (ILC2s), key players in tissue repair, are dysfunctional in UC and experimental colitis due to disrupted endoplasmic reticulum protein processing. We show that the pro-repair function of gut ILC2s depends on the IRE1α-Xbp1 branch of unfolded protein response (UPR), supported by IL-25 and suppressed by interferon-γ (IFN-γ). During colitis, loss of IL-25 and rise of IFN-γ hinder Xbp1 mRNA splicing, weakening ILC2s' ability to mediate tissue repair. Mechanistically, spliced Xbp1 drives folate-dependent one-carbon (1C) metabolism by promoting dihydrofolate reductase expression. Translationally, the 1C metabolite adenosine 5'-monophosphate alleviated colitis in both ILC2-specific Xbp1 knockout and wild-type mice. Our findings highlight the UPR's role in sensing gut environment to regulate ILC2 function and suggest folate-mediated 1C metabolism as a potential target for UC therapy.

Interferon regulatory factors (IRFs) are a family of transcription factors essential for immune system development and host defense. Beyond immunity, IRF6 plays an indispensable role in craniofacial development. Inborn errors of IRFs (IE-IRFs) are a group of rare monogenic disorders caused by damaging variants in the IRF family of genes. In this review, we comprehensively discuss known IE-IRFs and how they contribute to our understanding of human biology, and provide a framework for their diagnosis and treatment. The IRF transcription factors mediate a wide range of biological functions. Accordingly, genetic defects in individual IRFs give rise to diverse human phenotypes, including increased susceptibility to infection, impaired immune development, and even congenital anatomical anomalies. Our collective understanding of IE-IRFs is a powerful example of how integration of clinical care with mechanistic translational research can transform the lives of patients while simultaneously advancing our fundamental understanding of human biology.

Metastatic progression is a major cause of radiotherapy (RT) failure, yet the mechanisms linking RT to immune suppression and metastasis remain unclear. Here, we identify YTHDF2 as a radiation-induced immune checkpoint in dendritic cells (DCs). By analyzing patient biopsies from a clinical trial (NCT03223155), we discover that increased YTHDF2 expression in DCs after RT correlates with treatment failure after RT. Mechanistically, ionizing radiation induces SPI1, which drives transcription of Ythdf2 in DCs. Upregulated YTHDF2 promotes m6A-mediated degradation of Notch pathway regulators (Mfng, Aph1b, Aph1c), impairing MHC-I cross-presentation and CD8+ T cell activation, thereby facilitating tumor immune evasion and metastatic spread. Crucially, targeting YTHDF2 restores DC immunogenicity, enhances RT-induced tumor control, and improves DC-based cancer vaccines when combined with RT, providing a clinically actionable strategy to overcome RT resistance and metastasis.

Apoptotic cell (AC) corpses can be taken up by certain types of dendritic cell (DC), which cross-present dead cell-derived antigens. In this issue of JEM, Tam et al. (https://doi.org/10.1084/jem.20250887) reveal that GPR34, a lysophosphatidylserine receptor, promotes AC uptake and cross-presentation by type 1 DCs (cDC1s).

Currently, it remains largely unclear how MSI-H/dMMR tumors, despite heightened immune pathway activation and antigenic mutation accumulation, evade immune elimination and promote tumorigenesis. Our study showed that dMMR tumors accumulate cytosolic double-stranded DNA, activating the cGAS-IFN pathway and upregulating DNA-digesting enzyme TREX1. In immunocompetent mice, Trex1 depletion in MSI-H/dMMR tumors abolished tumor formation in a CD8+ T cell-dependent manner, suggesting its critical role in enabling these tumors to evade immune attack. Mechanistically, Trex1 loss amplified tumor-intrinsic cGAS-STING signaling, promoted the activation of CD8+ T cells, and triggered systemic antitumor immunity. Critically, ablating cGAS-STING signaling in MSI-H/dMMR tumors abolished the immune boost from TREX1 deletion, revealing the critical role MSI-H/dMMR tumor-intrinsic cGAS-STING pathway. Furthermore, Trex1 inhibition specifically reduced MSI-H/dMMR tumors growth in vivo, highlighting its clinical potential. Together, we identify the cGAS-STING-TREX1 loop as a key immune escape mechanism in MSI-H/dMMR cancers, suggesting TREX1 inhibition could enhance immunotherapy for these patients.

JAK2V617F causes >50% essential thrombocythemia (ET) and >90% polycythemia vera (PV). How such a single mutation causes distinct disorders remains a long-standing enigma. Here, we show that heterozygous JAK2V617F activates the transcription factor aryl hydrocarbon receptor (AhR), which biases MEP differentiation toward megakaryocytes in ET patients. In contrast, most PV patients' JAK2V617F exhibits a homozygous mutation that does not activate AhR. We found that JAK2V617F forms a heterodimer with JAK2 to recruit and activate STAT1, thereby inducing AhR activation and driving ET pathogenesis. However, JAK2 forms V617F homodimers in PV patients, which activate STAT5 and drive PV development. In addition to increasing platelet number, activated AhR may enhance platelet activity via the COX2-TXA2 axis. Importantly, targeting AhR inhibits thrombocytosis in JAK2V617F ET humanized mice. These findings not only elucidate the molecular mechanism of JAK2V617F ET but also provide a potential strategy for its treatment.