Journal of Experimental Medicine最新文献

Inflammatory signal termination is critical for the maintenance of homeostasis. Cyclic dinucleotides (CDNs) are second messengers that trigger inflammatory responses through the activation of the stimulator of IFN genes (STING) signaling platform. No broad-acting direct regulator of intracellular CDNs has been identified in mammals to date. We show that the DNA-dependent protein kinase catalytic subunit (DNA-PKcs), a major DNA damage response actor, directly interacts with the intracellular 2'3'-cGAMP CDN through its kinase domain, tempering STING activation. DNA-PKcs also acts on the 3'3'-cGAMP bacterial CDN and pharmacological STING agonists, impacting their bioactivity and ability to mount optimal antiviral responses. STING agonism has been considered as a therapeutic avenue to alleviate immunosuppression in human pathologies. By uncovering DNA-PKcs as a CDN signaling modulator and CDNs as inhibitors of DNA-PKcs kinase activity, we provide critical insights into CDN regulation, with implications for the development of STING-targeting therapeutics.

COPA syndrome is a rare monogenic autoinflammatory disease due to heterozygous mutations in COPA, encoding the coatomer subunit α. COPA syndrome demonstrates phenotypic overlap with STING-associated vasculopathy with onset in infancy (SAVI), the latter due to gain-of-function mutations in STING1. Indeed, STING activation is a key driver of the pathogenesis of COPA syndrome, and a recent report suggested that the presence of the common HAQ STING allele confers complete protection against the development of clinical disease in the context of pathogenic heterozygous mutations in COPA. Given the potential significance of this result for patient management, we investigated the STING HAQ haplotype status of a separate cohort of individuals segregating pathogenic mutations in COPA. In doing so, we ascertained five HAQ-negative, clinically asymptomatic individuals aged 30, 39, 39, 42, and 43 years at last evaluation, and an HAQ-positive male with kidney disease that we consider most likely attributable to the recurrent R233H mutation in COPA. Our findings challenge the suggestion that STING haplotype status is the sole determinant of clinical penetrance in COPA syndrome.

In the tumor microenvironment (TME), "exhausted" CD8+ T cells are classified into progenitor (Tpex) and terminally exhausted (Ttex) populations. Tpex cells, critically regulated by zinc finger and BTB domain containing 27 (Zbtb27)/Bcl6 transcription factor, could be reinvigorated during immune checkpoint blockade (ICB) therapy, while Ttex cells, characterized by stronger proliferation and cytotoxicity, play an indispensable role in tumor control. However, the mechanisms governing the differentiation into Ttex and their function remain not well understood. In this study, we identified that Zbtb32, highly expressed in CD8+ Ttex subset, is crucial for CD8+ T cells within tumors. Zbtb32, regulated by CD28 signaling, promotes the differentiation of CD8+ T cells into Ttex subset, enhancing their cytotoxicity, proliferation, and anti-tumor capability. Importantly, we found a competitive DNA binding between Zbtb32 and Bcl6, especially in regulation of Id2 expression. Thus, our findings demonstrate the pivotal role of Zbtb32 in CD8+ T cell anti-tumor function, with implications in cancer immunotherapy.

Loss of the lariat debranching enzyme DBR1 causes cytoplasmic accumulation of intron lariats, but why this reduces cell-intrinsic immunity is unclear. Here, we show that intronic inverted repeats Alu (IR Alus), normally degraded after splicing, form long double-stranded RNA (dsRNA) structures when lariats escape recycling. Viral introns evolve under pressure to avoid dsRNA, whereas human introns are enriched for them. Using computational, immunostaining, and genomic approaches, we demonstrate that DBR1 deficiency elevates cytoplasmic dsRNA and attenuates RNase L and PKR signaling. Our data suggest high levels of IR Alu dsRNA titrate PKR, potentially providing a mechanistic explanation for viral susceptibility in DBR1-deficient cells. Cytoplasmic RIP-seq against dsRNA finds introns to be a more abundant source of IR Alus than 3' UTRs in WT cells. Our findings suggest the high load of IR Alus in introns creates a situation where the efficiency of lariat recycling is a powerful modulator of endogenous dsRNA levels in human cells.

Ly6Chigh monocytes, previously recognized as a pro-inflammatory subset, play critical roles in secondary neuroinflammation in the stroke brain. Growing evidence reveals increased infiltration of myeloid cells with substantial heterogeneity, raising the question of how Ly6Chigh monocyte-derived macrophages in the stroke brain adapt to the ischemic environment. Here, by combining analysis of stroke patient samples with in vivo and in vitro murine studies and single-cell transcriptomic profiling, we identify hypoxia-inducible lipid droplet-associated protein (Hilpda)/hypoxia-inducible protein 2 (HIG2) as a critical mediator of anti-inflammatory property of Ly6ChighLy6Glow monocyte-derived macrophages in the stroke brain. Mechanistically, HIG2 promotes phosphatidylcholine synthesis via Hif1α-dependent transcriptional regulation of choline kinase α, initiating lipid metabolism reprogramming that underpins the anti-inflammatory phenotype of Ly6ChighLy6Glow monocyte-derived macrophages in the ischemic brain after stroke. Intranasal delivery of recombinant HIG2 protein improves neurological outcomes after stroke. These findings suggest that targeting HIG2 might represent a novel immunometabolic strategy to mitigate poststroke neuroinflammation.

While inputs regulating CD4+ T helper (Th) cell differentiation are well defined, the integration of downstream signaling with transcriptional and epigenetic programs that define Th lineage identity remains incompletely resolved. PI3K signaling is a critical regulator of T cell function; activating mutations affecting PI3Kδ result in an immunodeficiency with multiple T cell defects. Using mice expressing activated PI3Kδ, we found aberrant expression of proinflammatory Th1 signature genes under Th2-inducing conditions, both in vivo and in vitro. This dysregulation was driven by a PI3Kδ-IL-2-Foxo1 signaling amplification loop, fueling Foxo1 inactivation, loss of Th2 lineage restriction, and extensive epigenetic reprogramming. Surprisingly, ablation of Fasl, a Foxo1-repressed gene, normalized both Th2 differentiation and TCR signaling. BioID and imaging revealed Fas interactions with TCR signaling components, which were supported by Fas-mediated potentiation of TCR signaling that could occur in the absence of FADD. Our results highlight Fas-FasL signaling as a critical intermediate in phenotypes driven by activated PI3Kδ, thereby linking two key pathways of immune dysregulation.

Many cancer patients do not benefit from current immunotherapies. This lack of efficacy may be, in part, due to insufficient priming and activation of T cells. Here, we show that activation of liver-X-receptors (LXRs) promotes adaptive anti-tumor immunity by enhancing priming of T cells. Genetic LXR deletion in the host and depletion of dendritic and CD8+ T cells, but not of macrophages, abrogated anti-tumor effects of LXR-agonistic therapy. In cross-presentation assays, LXR agonism promoted T cell activation upon DC/T cell cross talk. Genetic deletion of LXRs in T cells, but not in dendritic cells, blunted this effect. Dissection of the temporal dynamics of LXR-enhanced T cell effector function showed that LXR agonism rendered T cells more receptive to adopting effector states upon stimulation. Consistently, LXR agonist therapy elicited T cell expansion in cancer patients enrolled in a phase I trial. Our findings establish LXR activation as an effective approach for enhancing T cell priming.

Macrophages, as key sentinel cells of the innate immune system, can retain memory of prior stimulus exposure. IFNγ plays a central role in maintaining trained immunity in vivo and can induce potent memory in macrophages. Such memory is associated with the formation of de novo enhancers that alter gene expression responses to subsequent stimuli. However, how such enhancers are maintained after cytokine exposure remains unclear. We report that the mechanism underlying durable IFNγ-induced enhancers is not cell intrinsic. IFNγ-treated macrophages continue to exhibit JAK/STAT signaling days after cytokine removal. Blocking IFNγ signaling with a JAK inhibitor or anti-IFNγ neutralizing antibodies after cytokine removal is sufficient to reverse IFNγ-induced enhancers and erase the potentiated state of the treated macrophages. Our findings suggest that epigenetic changes in macrophages do not inherently encode innate immune memory or a "potentiated" macrophage state, but in fact are themselves dependent on ongoing signaling from cytokines sequestered at the cell surface.

The brain encodes and stores information about peripheral inflammation and can directly recapitulate prior inflammatory responses. However, whether individual cytokines activate specific neural circuits to produce distinct physiological responses remains unknown. To address this fundamental question, we mapped brain-wide responses to IL-1β and found prominent engagement of the bed nucleus of the stria terminalis (BNST). Using targeted recombination in active populations, snRNA sequencing, and circuit tracing, we discovered that corticotropin-releasing hormone-expressing BNST neurons encode IL-1β signals. Chemogenetic reactivation of these neurons precisely recapitulates the physiological signatures of IL-1β exposure with increased circulating IL-6 and corticosterone and tachycardia. These responses require a defined BNST→paraventricular nucleus→rostral ventrolateral medulla→β receptor adrenergic signaling pathway. Critically, restraint stress also activates these BNST IL-1β-encoding neurons to generate the same physiological responses. Our findings establish how a single inflammatory mediator uses a precise neural circuit to activate systemic responses and provide mechanistic insight into the neuroimmune interactions underlying stress-related psychiatric and inflammatory diseases.

Antibody-mediated immune responses in mucosal tissues are critical for defending against pathogens while maintaining homeostasis with commensals. Nasal vaccination aims to induce local protection in the upper airway mucosa. Although B cell-driven immunity is well characterized in gut-associated lymphoid tissues such as Peyer's patches and mesenteric LNs, much less is known about analogous processes in the upper airways. Here, we show that B cell receptor (BCR) affinity and CCR6 regulate germinal center (GC) seeding and class-switch recombination (CSR) to IgA in nasal-associated lymphoid tissue (NALT) following nasal vaccination. B cells bearing low-affinity BCRs failed to upregulate CCR6 and did not support T follicular helper cell differentiation or seed GCs in the NALT. CCR6-deficient B cells were unable to migrate to the NALT subepithelial dome or undergo IgA CSR and seed GC effectively in response to nasal vaccination or commensal bacteria signals. Thus, effective targeting of B cell clones to induce CCR6 expression is essential for nasal vaccine design.