Abstract: STAT6 (signal transducer and activator of transcription 6) is a transcription factor that plays a central role in the pathophysiology of allergic inflammation. We have identified 16 patients from 10 families spanning three continents with a profound phenotype of early-life onset allergic immune dysregulation, widespread treatment-resistant atopic dermatitis, hypereosinophilia with esosinophilic gastrointestinal disease, asthma, elevated serum IgE, IgE-mediated food allergies, and anaphylaxis. The cases were either sporadic (seven kindreds) or followed an autosomal dominant inheritance pattern (three kindreds). All patients carried monoallelic rare variants in STAT6 and functional studies established their gain-of-function (GOF) phenotype with sustained STAT6 phosphorylation, increased STAT6 target gene expression, and TH2 skewing. Precision treatment with the anti–IL-4Rα antibody, dupilumab, was highly effective improving both clinical manifestations and immunological biomarkers. This study identifies heterozygous GOF variants in STAT6 as a novel autosomal dominant allergic disorder. We anticipate that our discovery of multiple kindreds with germline STAT6 GOF variants will facilitate the recognition of more affected individuals and the full definition of this new primary atopic disorder.

Abstract: Neutrophil infiltration is a hallmark of periodontitis, a prevalent oral inflammatory condition in which Th17-driven mucosal inflammation leads to destruction of tooth-supporting bone. Herein, we document that neutrophil extracellular traps (NETs) are early triggers of pathogenic inflammation in periodontitis. In an established animal model, we demonstrate that neutrophils infiltrate the gingival oral mucosa at early time points after disease induction and expel NETs to trigger mucosal inflammation and bone destruction in vivo. Investigating mechanisms by which NETs drive inflammatory bone loss, we find that extracellular histones, a major component of NETs, trigger upregulation of IL-17/Th17 responses, and bone destruction. Importantly, human findings corroborate our experimental work. We document significantly increased levels of NET complexes and extracellular histones bearing classic NET-associated posttranslational modifications, in blood and local lesions of severe periodontitis patients, in the absence of confounding disease. Our findings suggest a feed-forward loop in which NETs trigger IL-17 immunity to promote immunopathology in a prevalent human inflammatory disease.

Abstract: Clodronate liposomes (Clo-Lip) have been widely used to deplete mononuclear phagocytes (MoPh) to study the function of these cells in vivo. Here, we revisited the effects of Clo-Lip together with genetic models of MoPh deficiency, revealing that Clo-Lip exert their anti-inflammatory effects independent of MoPh. Notably, not only MoPh but also polymorphonuclear neutrophils (PMN) ingested Clo-Lip in vivo, which resulted in their functional arrest. Adoptive transfer of PMN, but not of MoPh, reversed the anti-inflammatory effects of Clo-Lip treatment, indicating that stunning of PMN rather than depletion of MoPh accounts for the anti-inflammatory effects of Clo-Lip in vivo. Our data highlight the need for a critical revision of the current literature on the role of MoPh in inflammation.

Abstract: Harker and Lloyd review the multifaceted roles of Th2 cells in human asthma, highlighting their influence of tissue location and disease severity. They also explore how Th2 cells and their cytokines have been targeted for biologic therapies for asthma patients.

Abstract: In cancer, persistent antigens drive CD8+ T cell differentiation into exhausted progenitor (Texprog) and terminally exhausted (Texterm) cells. However, how the extrinsic and intrinsic regulatory mechanisms cooperate during this process still remains not well understood. Here, we found that STAT3 signaling plays essential roles in promoting intratumor Texterm cell development by enhancing their effector functions and survival, which results in better tumor control. In tumor microenvironments, STAT3 is predominantly activated by IL-10 and IL-21, but not IL-6. Besides, STAT3 also plays critical roles in the development and function of terminally differentiated effector CD8+ T cells in acute infection. Mechanistically, STAT3 transcriptionally promotes the expression of effector function-related genes, while it suppresses those expressed by the progenitor Tex subset. Moreover, STAT3 functions in collaboration with BATF and IRF4 to mediate chromatin activation at the effector gene loci. Thus, we have elucidated the roles of STAT3 signaling in terminally differentiated CD8+ T cell development, especially in cancer, which benefits the development of more effective immunotherapies against tumors.

Abstract: Gervais et al. show that auto-Abs neutralizing type I IFNs and pre-existing infection underlie ∼40% of cases of West Nile virus (WNV) encephalitis. Blood and cerebrospinal fluid auto-Abs neutralize the protective activity of type I IFNs against WNV in vitro.

Abstract: Retinitis pigmentosa (RP) is an inherited retinal dystrophy causing progressive and irreversible loss of retinal photoreceptors. Here, we developed a genome-editing tool characterized by the versatility of prime editors (PEs) and unconstrained PAM requirement of a SpCas9 variant (SpRY), referred to as PESpRY. The diseased retinas of Pde6b-associated RP mouse model were transduced via a dual AAV system packaging PESpRY for the in vivo genome editing through a non-NGG PAM (GTG). The progressing cell loss was reversed once the mutation was corrected, leading to substantial rescue of photoreceptors and production of functional PDE6β. The treated mice exhibited significant responses in electroretinogram and displayed good performance in both passive and active avoidance tests. Moreover, they presented an apparent improvement in visual stimuli-driven optomotor responses and efficiently completed visually guided water-maze tasks. Together, our study provides convincing evidence for the prevention of vision loss caused by RP-associated gene mutations via unconstrained in vivo prime editing in the degenerating retinas.

Abstract: Combining whole-tissue imaging and single-cell RNA sequencing datasets, Tauber et al. present a pan-organ analysis of mast cells in mice and humans at steady state, revealing an unexpected heterogeneity of mast cell populations across tissues and species.

Abstract: Age-associated B cells (ABCs) are formed under inflammatory conditions and are considered a type of memory B cell (MBC) expressing the transcription factor T-bet. In SLE, ABC frequency is correlated with disease, and they are thought to be the source of autoantibody-secreting cells. However, in inflammatory conditions, whether autoreactive B cells can become resting MBCs is uncertain. Further, the phenotypic identity of ABCs and their relationship to other B cell subsets, such as plasmablasts, is unclear. Whether ABCs directly promote disease is untested. Here we report, in the MRL/lpr SLE model, unexpected heterogeneity among ABC-like cells for expression of the integrins CD11b and CD11c, T-bet, and memory or plasmablast markers. Transfer and labeling studies demonstrated that ABCs are dynamic, rapidly turning over. scRNA-seq identified B cell clones present in multiple subsets, revealing that ABCs can be plasmablast precursors or undergo cycles of reactivation. Deletion of CD11c-expressing B cells revealed a direct role for ABC-like B cells in lupus pathogenesis.

Abstract: STING signaling is at the center of multiple autoinflammatory and neurodegenerative diseases. The authors review how STING trafficking influences signaling, propose a model of tonic STING signaling, and discuss an emerging link between dysregulated STING trafficking and neurodegenerative disease.

Abstract: Both DCs and monocytes capture antigen for presentation to lymph node T cells. Here, Rawat et al. show that DCs use the chemokine receptor CCR7, while monocytes follow chemokines secreted by migratory DCs to reach the nodes and control immunity.

Abstract: The meningeal lymphatic network enables the drainage of cerebrospinal fluid (CSF) and facilitates the removal of central nervous system (CNS) waste. During aging and in Alzheimer's disease, impaired meningeal lymphatic drainage promotes the buildup of toxic misfolded proteins in the CNS. Reversing this age-related dysfunction represents a promising strategy to augment CNS waste clearance; however, the mechanisms underlying this decline remain elusive. Here, we demonstrate that age-related alterations in meningeal immunity underlie this lymphatic impairment. Single-cell RNA sequencing of meningeal lymphatic endothelial cells from aged mice revealed their response to IFNγ, which was increased in the aged meninges due to T cell accumulation. Chronic elevation of meningeal IFNγ in young mice via AAV-mediated overexpression attenuated CSF drainage-comparable to the deficits observed in aged mice. Therapeutically, IFNγ neutralization alleviated age-related impairments in meningeal lymphatic function. These data suggest manipulation of meningeal immunity as a viable approach to normalize CSF drainage and alleviate the neurological deficits associated with impaired waste removal.

Abstract: ZBP1 is an innate immune sensor for double-stranded nucleic acids adopting the Z conformation. Z-RNA/DNA is generated during viral infections and in autoinflammation and cancer. By inducing regulated cell death and proinflammatory signaling, ZBP1 plays multifaceted roles in disease pathology.

Abstract: In the DONIMI trial, a baseline IFN-γ signature enables prospective selection of patients who can benefit from anti-PD-1 monotherapy. In contrast to results of our murine melanoma model, domatinostat (a class I HDAC inhibitor) does not add benefit to neoadjuvant anti-PD-1 ± anti-CTLA-4 in patients.

Abstract: MyD88- and IRAK-4–deficient patients have a higher risk of hypoxemic COVID-19 pneumonia than individuals of similar age in the general population, due to impaired TLR7-dependent type I IFN production.

Abstract: Petkova et al. identify a new Ptx3-positive immune-interacting subtype of lymphatic endothelial cells, iLECs, that drive oncogenic PI3K-driven lymphatic malformations. These cells produce chemokines that recruit pro-lymphangiogenic macrophages, which in turn promote pathological lymphatic vessel growth.

Abstract: The functional role of CD8+ lymphocytes in tuberculosis remains poorly understood. We depleted innate and/or adaptive CD8+ lymphocytes in macaques and showed that loss of all CD8α+ cells (using anti-CD8α antibody) significantly impaired early control of Mycobacterium tuberculosis (Mtb) infection, leading to increased granulomas, lung inflammation, and bacterial burden. Analysis of barcoded Mtb from infected macaques demonstrated that depletion of all CD8+ lymphocytes allowed increased establishment of Mtb in lungs and dissemination within lungs and to lymph nodes, while depletion of only adaptive CD8+ T cells (with anti-CD8β antibody) worsened bacterial control in lymph nodes. Flow cytometry and single-cell RNA sequencing revealed polyfunctional cytotoxic CD8+ lymphocytes in control granulomas, while CD8-depleted animals were unexpectedly enriched in CD4 and γδ T cells adopting incomplete cytotoxic signatures. Ligand-receptor analyses identified IL-15 signaling in granulomas as a driver of cytotoxic T cells. These data support that CD8+ lymphocytes are required for early protection against Mtb and suggest polyfunctional cytotoxic responses as a vaccine target.

Abstract: There is unprecedented spread of highly pathogenic avian influenza A H5N1 viruses in bird species on five continents, and many reports of infections in mammals most likely resulting from consumption of infected birds. As H5N1 viruses infect more species, their geographical range increases and more viral variants are produced that could have new biological properties including adaptation to mammals and potentially to humans. This highlights the need to continually monitor and assess mammalian-origin H5N1 clade 2.3.4.4b viruses for the presence of mutations that could potentially increase their pandemic risk for humans. Fortunately, to date there have been a limited number of human cases, but infection of mammals increases the opportunity for the virus to acquire mutations that enhance efficient infection, replication, and spread in mammals, properties that have not been seen in these viruses in the past.

Abstract: The fundamental importance of the role of human B cells in host defense against infectious diseases has been established by the discovery of inborn errors of immunity that disrupt B cell development, differentiation, or function. These findings have laid the groundwork for understanding mechanisms of disease and revealing pathways to improve humoral immunity and treat disease.

Abstract: CD8 tissue-resident memory T (TRM) cells provide frontline protection at barrier tissues; however, mechanisms regulating TRM cell development are not completely understood. Priming dictates the migration of effector T cells to the tissue, while factors in the tissue induce in situ TRM cell differentiation. Whether priming also regulates in situ TRM cell differentiation uncoupled from migration is unclear. Here, we demonstrate that T cell priming in the mesenteric lymph nodes (MLN) regulates CD103+ TRM cell differentiation in the intestine. In contrast, T cells primed in the spleen were impaired in the ability to differentiate into CD103+ TRM cells after entry into the intestine. MLN priming initiated a CD103+ TRM cell gene signature and licensed rapid CD103+ TRM cell differentiation in response to factors in the intestine. Licensing was regulated by retinoic acid signaling and primarily driven by factors other than CCR9 expression and CCR9-mediated gut homing. Thus, the MLN is specialized to promote intestinal CD103+ CD8 TRM cell development by licensing in situ differentiation.

Abstract: Phagocytosis is a key macrophage function, but how phagocytosis shapes tumor-associated macrophage (TAM) phenotypes and heterogeneity in solid tumors remains unclear. Here, we utilized both syngeneic and novel autochthonous lung tumor models in which neoplastic cells express the fluorophore tdTomato (tdTom) to identify TAMs that have phagocytosed neoplastic cells in vivo. Phagocytic tdTompos TAMs upregulated antigen presentation and anti-inflammatory proteins, but downregulated classic proinflammatory effectors compared to tdTomneg TAMs. Single-cell transcriptomic profiling identified TAM subset-specific and common gene expression changes associated with phagocytosis. We uncover a phagocytic signature that is predominated by oxidative phosphorylation (OXPHOS), ribosomal, and metabolic genes, and this signature correlates with worse clinical outcome in human lung cancer. Expression of OXPHOS proteins, mitochondrial content, and functional utilization of OXPHOS were increased in tdTompos TAMs. tdTompos tumor dendritic cells also display similar metabolic changes. Our identification of phagocytic TAMs as a distinct myeloid cell state links phagocytosis of neoplastic cells in vivo with OXPHOS and tumor-promoting phenotypes.

Abstract: Inhibition of CDK4/6 and lysosome function overcomes c-MYC–mediated cell cycle entry in the face of trametinib and chloroquine co-treatment in pancreatic cancer.

Abstract: The ZAKα-driven ribotoxic stress response (RSR) is activated by ribosome stalling and/or collisions. Recent work demonstrates that RSR also plays a role in innate immunity by activating the human NLRP1 inflammasome. Here, we report that ZAKα and NLRP1 sense bacterial exotoxins that target ribosome elongation factors. One such toxin, diphtheria toxin (DT), the causative agent for human diphtheria, triggers RSR-dependent inflammasome activation in primary human keratinocytes. This process requires iron-mediated DT production in the bacteria, as well as diphthamide synthesis and ZAKα/p38-driven NLRP1 phosphorylation in host cells. NLRP1 deletion abrogates IL-1β and IL-18 secretion by DT-intoxicated keratinocytes, while ZAKα deletion or inhibition additionally limits both pyroptotic and inflammasome-independent non-pyroptotic cell death. Consequently, pharmacologic inhibition of ZAKα is more effective than caspase-1 inhibition at protecting the epidermal barrier in a 3D skin model of cutaneous diphtheria. In summary, these findings implicate ZAKα-driven RSR and the NLRP1 inflammasome in antibacterial immunity and might explain certain aspects of diphtheria pathogenesis.

Abstract: The microbiome influences response to immunotherapy, including immune-related adverse events (irAEs) with checkpoint inhibitors. Wang, Jenq, et al. discuss microbiome contributions to irAEs by focusing on major bacterial taxa, potential immune mechanisms, and clinical opportunities for microbiome modulation to treat irAEs.

Abstract: The field of asthma has undergone a dramatic change in recent years. Advances in our understanding of type 2 airway inflammation have driven the discovery of monoclonal antibodies targeting specific aspects of the immune pathway. In landmark trials, these drugs have shown efficacy in reducing asthma attacks and exposure to oral corticosteroids, important causes of morbidity in people with asthma. Our review explores the key features of type 2 inflammation in asthma and summarizes the clinical trial evidence of the novel monoclonal antibody treatments and future avenues for treatment.

Abstract: The hallmark of tuberculosis (TB) is the formation of immune cell-enriched aggregates called granulomas. While granulomas are pathologically diverse, their tissue-wide heterogeneity has not been spatially resolved at the single-cell level in human tissues. By spatially mapping individual immune cells in every lesion across entire tissue sections, we report that in addition to necrotizing granulomas, the human TB lung contains abundant non-necrotizing leukocyte aggregates surrounding areas of necrotizing tissue. These cellular lesions were more diverse in composition than necrotizing lesions and could be stratified into four general classes based on cellular composition and spatial distribution of B cells and macrophages. The cellular composition of non-necrotizing structures also correlates with their proximity to necrotizing lesions, indicating these are foci of distinct immune reactions adjacent to necrotizing granulomas. Together, we show that during TB, diseased lung tissue develops a histopathological superstructure comprising at least four different types of non-necrotizing cellular aggregates organized as satellites of necrotizing granulomas.

Abstract: Commensal bacteria, such as Bacteroides fragilis, triggers type I IFN and IL-27 in DCs to influence Tregs through IL27RA signaling. The IFN gene signature in Tregs during inflammation highlights the role of the microbiota in maintaining tonic IFN to promote immune tolerance.

Abstract: Recent studies suggest that training of innate immune cells such as tissue-resident macrophages by repeated noxious stimuli can heighten host defense responses. However, it remains unclear whether trained immunity of tissue-resident macrophages also enhances injury resolution to counterbalance the heightened inflammatory responses. Here, we studied lung-resident alveolar macrophages (AMs) prechallenged with either the bacterial endotoxin or with Pseudomonas aeruginosa and observed that these trained AMs showed greater resilience to pathogen-induced cell death. Transcriptomic analysis and functional assays showed greater capacity of trained AMs for efferocytosis of cellular debris and injury resolution. Single-cell high-dimensional mass cytometry analysis and lineage tracing demonstrated that training induces an expansion of a MERTKhiMarcohiCD163+F4/80low lung-resident AM subset with a proresolving phenotype. Reprogrammed AMs upregulated expression of the efferocytosis receptor MERTK mediated by the transcription factor KLF4. Adoptive transfer of these trained AMs restricted inflammatory lung injury in recipient mice exposed to lethal P. aeruginosa. Thus, our study has identified a subset of tissue-resident trained macrophages that prevent hyperinflammation and restore tissue homeostasis following repeated pathogen challenges.

Abstract: Obesity is characterized by chronic systemic inflammation and enhances cancer metastasis and mortality. Obesity promotes breast cancer metastasis to lung in a neutrophil-dependent manner; however, the upstream regulatory mechanisms of this process remain unknown. Here, we show that obesity-induced monocytes underlie neutrophil activation and breast cancer lung metastasis. Using mass cytometry, obesity favors the expansion of myeloid lineages while restricting lymphoid cells within the peripheral blood. RNA sequencing and flow cytometry revealed that obesity-associated monocytes resemble professional antigen-presenting cells due to a shift in their development and exhibit enhanced MHCII expression and CXCL2 production. Monocyte induction of the CXCL2-CXCR2 axis underlies neutrophil activation and release of neutrophil extracellular traps to promote metastasis, and enhancement of this signaling axis is observed in lung metastases from obese cancer patients. Our findings provide mechanistic insight into the relationship between obesity and cancer by broadening our understanding of the interactive role that myeloid cells play in this process.