Thymic central tolerance is crucial for preventing autoimmunity, but its contribution to tumor immune evasion remains poorly understood. Here, we demonstrate that plasmacytoid dendritic cells (pDCs) in the thymus have two distinct subsets, accumulating in the thymus of tumor-bearing mice, contributing to immune tolerance through clonal deletion of tumor-specific T cells and reducing newly generated T cells. Mechanistically, common dendritic cell progenitor-derived pDCs (CDP-pDCs) capture tumor antigens and migrate to the thymus in a CCR9-dependent manner, where they present these antigens to induce clonal deletion of tumor-specific T cells. Concurrently, tumor progression inhibits T cell generation by promoting the accumulation of common lymphoid progenitor-derived pDCs (CLP-pDCs) within the thymus, which further produce type I interferon to alter thymic function. CCR9 deficiency prevents thymic accumulation of both pDCs, enhancing antitumor immunity and reducing tumor growth. Our findings reveal a previously unrecognized mechanism by which tumors hijack the physiological system to establish central tolerance against peripheral antigens, thereby promoting tolerance against themselves.

BACKGROUND:Pulmonary hypertension (PH) is a progressive cardiopulmonary disorder characterized by vascular remodeling, abnormal vasoconstriction of small lung arteries, and right heart failure. Hypoxia causes vascular damage, leading to vessel stenosis or occlusion by aberrant endothelial cells, hypertrophy of the tunica media, and thrombus formation. But the precise molecular mechanisms underlying the pathology of PH have been uncertain. METHODS:To investigate the pathogenic role of Myl (myosin light chain) 9/12 in PH, we utilized the Sugen/hypoxia mouse model, generated by administration of the VEGF (vascular endothelial growth factor) receptor inhibitor SU5416 under hypoxic conditions (10% O2). Lung tissues of patients with PH and human lung microvascular endothelial cells were used to examine their endothelial changes. Platelet-specific Myl9-deficient mice were generated to determine the contribution of platelet-derived Myl9 to the development of PH. The therapeutic efficacy of the anti-Myl9/12 antibody was evaluated by hemodynamics, histological analyses, and single-cell RNA sequencing. Furthermore, serum MYL9, MYL12A, and MYL12B levels were measured in patients with PH and analyzed for clinical correlation. RESULTS:We identified microthrombi containing Myl9/12 in both patients with PH and the PH mouse model. Platelet-derived Myl9 partially contributed to PH development by promoting cellular infiltration. Furthermore, hypoxia upregulated the expression of Myl9/12 through EPAS1 (endothelial PAS domain protein 1) in proliferated lung vascular endothelial cells and induced the release of Myl9/12 into the extracellular space. Anti-Myl9/12 antibody treatment attenuated PH in the mouse model by reducing microthrombus formation, inflammatory cell infiltration, tissue hypoxia, and vascular remodeling. The established PH in Sugen/hypoxia mice was also attenuated by the treatment with anti-Myl9/12 antibody. Moreover, serum levels of Myl9 but not MYL12A or MYL12B levels reflected the severity of PH in patients. CONCLUSIONS:These findings reveal that Myl9/12 play a pathogenic role in developing vascular lesions of PH and could be a new therapeutic target for PH.

Invariant natural killer T (iNKT) cells, upon activation, exhibit antitumor roles by bridging innate and acquired immunity. To overcome the challenges in producing iNKT cells from patients with cancer, we previously developed allogeneic human induced pluripotent stem cell-derived iNKT (iPSC-iNKT) cells. However, the activation of iPSC-iNKT cells by glycolipid ligands remains a critical step for iNKT cell-mediated cancer therapy. To show the effect of iPSC-iNKT cell-mediated antitumor immunity, in this preclinical study, by taking advantage of a human immune cell-transplanted patient-derived xenograft model using human IL-7/15 knock-in NSG mice, we demonstrate that a combination of iPSC-iNKT cells and α-galactosylceramide-pulsed antigen-presenting cells (αGalCer/APC) induces robust antitumor effects. Single-cell analysis of tumor-infiltrating lymphocytes revealed that this combination therapy uniquely expanded tumor-reactive memory-phenotype CD4 and CD8 T cells. Taken together, upon activation by αGalCer/APC, iPSC-iNKT cells are capable of effectively inducing antitumor T cell immunity, making them a promising tool for generating personalized antitumor T cell immunity.

Hepatosteatosis is a common metabolic disorder. Bile acids influence hepatosteatosis, immune function, and incretin secretion. However, whether bile acids mediate hepatosteatosis through these immune or endocrine pathways remain unknown. Here, we identify supplementation with hyodeoxycholic acid (HDCA) in high-fat diet-fed mice increases hepatic iNKT cells and elevates circulating GLP-1, both upregulating fatty acid oxidation genes in a PPARα-dependent manner. Mechanistically, HDCA increases iNKT cells and IFN-γ production that promotes hepatic lipid catabolism, thereby attenuating triglyceride accumulation in wild-type (WT) mice, but not in iNKT cell-deficient (Ja18-/-) and PPARα knockout (Ppara-/-) mice. By contrast, the GLP-1 receptor agonist suppresses high-fat diet-induced steatosis in WT and Ja18-/- mice, but not in Ppara-/- and GLP-1 receptor knockout (Glp1r-/-) mice. Furthermore, anti-steatotic effect of HDCA is nullified in Glp1r-/- mice. Consequently, HDCA alleviates hepatosteatosis through dual mechanisms; an iNKT cell/IFN-γ immunometabolic- and GLP-1-dependent pathways. These findings highlight HDCA as a promising multi-target therapeutic strategy for hepatosteatosis.

Tissue-resident memory T cells (TRM cells) reside in nonlymphoid tissues and provide the first line of defense against pathogens. A subset of TRM cells can egress from nonlymphoid tissues into the circulation. However, the functional consequences and the extent of epigenetic imprinting in recirculating TRM cells remain unknown. We herein demonstrate that in CD4+ TRM cells, the CD69-S1PR1 axis controls tissue residency and that interrupting this axis results in ablation of lung CD4+ TRM cells. A subpopulation of CD69+CD4+ TRM cells reentered circulation via lymphatic vessels, where they epigenetically maintained the characteristics of TRM cells in both mice and humans. Circulating Ex-lung-TRM cells in mice caused enhanced skin inflammation compared to circulating memory cells. Furthermore, we identified GPR183 and CD161 as potential markers of Ex-TRM in human peripheral blood mononuclear cells. In chronic inflammatory diseases, the transposition of allergic inflammation to multiple tissues may therefore occur via recirculation of tissue-imprinted memory CD4+ T cells.

Tumor-specific CD8+ T cells play a pivotal role in anti-tumor immunity. Here, we review the heterogeneity of CD8+ T cell subsets during tumor progression. While both acute and chronic viral infections induce distinct CD8+ T cell responses, chronic responses are also observed during tumor development. Chronic immune responses have traditionally been considered to represent a dysfunctional state of CD8+ T cells, whereas the identification of TCF1+ stem-like CD8+ T cells has highlighted their importance in anti-tumor immunity. During tumor progression, TCF1+ stem-like CD8+ T cells differentiate into cytotoxic Tim-3+ terminally differentiated CD8+ T cells through mechanisms that remain largely unknown. We recently identified CD69 as an important regulator of chronic CD8+ T cell responses and showed that blocking CD69 function, either through the administration of anti-CD69 antibody (Ab) or genetic knockout, enhanced the generation of cytotoxic Tim-3+ terminally differentiated CD8+ T cells in both tumor-draining lymph nodes (TDLNs) and the tumor microenvironment (TME), thereby enhancing the anti-tumor immune response. These findings suggest that CD69 is an attractive therapeutic target that controls the chronic anti-tumor CD8+ T cell response.

A unique subpopulation of memory T helper 2 (TH2) cells expressing the interleukin-33 (IL-33) receptor ST2 drives allergic disease pathogenesis. However, the immunometabolic mechanisms that induce ST2hi memory TH2 cells remain unclear. We show using a mouse model of chronic allergic airway inflammation that long-chain unsaturated fatty acids (LC-UFAs) accumulate in the inflammatory milieu during chronic airway inflammation. Activated TH2 cells take up LC-UFAs, transiently store them in lipid droplets (LDs), and catabolize LDs through lipolysis and microlipophagy. LD catabolism regulated by adipose triglyceride lipase (ATGL) activates peroxisome proliferator-activated receptor γ (PPARγ). PPARγ then binds the Il1rl1 locus encoding ST2 and induces ST2hi effector and memory TH2 cells. In eosinophilic chronic rhinosinusitis, CD45RO+ CD4 T cells in nasal polyps exhibit microlipophagy and an accessible IL1RL1 enhancer, indicating that these mechanisms are conserved in humans. Thus, the storage and catabolism of inflammatory milieu-derived LC-UFAs direct pathogenic adaptive type 2 immunity, offering potential therapeutic strategies for persistent allergic inflammation.

Invariant natural killer T (iNKT) cells differentiate into at least three distinct subsets within the thymus, with each subset's frequency varying considerably among mouse strains; however, the molecular mechanisms involved remain unclear. We herein report that iNKT cell lineage diversity results from the significant expansion of iNKT2 cells with limited T cell receptor (TCR) diversity in BALB/c mice and the selection of iNKT1 cells with significantly diverse TCRs in B6 mice. Furthermore, signaling lymphocytic-activation molecule family 6 (SLAMF6) expression on immature thymocytes significantly differs among mouse strains, with the low expression of SLAMF6 on BALB/c immature thymocytes resulting in high "basal TCR signaling" in preselected DP thymocytes, associated with iNKT cell expansion. Our data suggest that the expression level of SLAMF6 on immature thymocytes affects basal TCR signaling in preselected DP thymocytes, which may influence thymocyte development in a T-cell subset.

Glomerular inflammation and podocyte loss are the hallmarks of chronic kidney disease (CKD) progression. Understanding how podocytes and their microenvironment regulate inflammation is critical for developing effective therapies. In this study, we identified C-C chemokine ligand 5 (CCL5) as an inflammatory mediator elevated in injured podocytes, based on analyses of both human kidney biopsies and mouse models of CKD. We discovered that CCL5 exerts paradoxical effects in nephropathy; while it protects podocytes in vitro, it exacerbates glomerular injury in vivo. Recombinant CCL5 and podocyte-specific CCL5 overexpression promoted cell survival and reduced apoptosis in cultured podocytes. However, in adriamycin-induced nephropathy, CCL5 worsened glomerular injury, increasing proteinuria, glomerulosclerosis, and podocyte loss. Bone marrow (BM) transplantation experiments revealed that CCL5 in BM-derived cells - not kidney-resident cells - drove disease progression. CCL5 deficiency in BM-derived cells conferred protection by increasing reparative M2 macrophages, whereas endogenous CCL5 promoted M1 polarization, inhibited M2 differentiation, and triggered M2-to-M1 transition. These findings demonstrate that while CCL5 supports podocyte survival, its expression in BM-derived cells promotes inflammatory macrophage phenotypes and glomerular injury. The harmful immune effects of CCL5 in BM-derived cells outweigh its podocyte-protective role, highlighting the importance of cell-targeted strategies to mitigate kidney damage.

Figure S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11

This year at JEM, we are highlighting women in science by sharing their stories and amplifying their voices. In this Viewpoint, we hear from a cross section of women, across multiple research fields, discussing their science and the process of setting up a lab as an independent researcher.

Theiler’s murine encephalomyelitis virus (TMEV) infection has been used as a mouse model for two virus-induced organ-specific immune-mediated diseases. TMEV-induced demyelinating disease (TMEV-IDD) in the central nervous system (CNS) is a chronic inflammatory disease with viral persistence and an animal model of multiple sclerosis (MS) in humans. TMEV infection can also cause acute myocarditis with viral replication and immune cell infiltration in the heart, leading to cardiac fibrosis. Since platelets have been reported to modulate immune responses, we aimed to determine the role of platelets in TMEV infection. In transcriptome analyses of platelets, distinct sets of immune-related genes, including major histocompatibility complex (MHC) class I, were up- or downregulated in TMEV-infected mice at different time points. We depleted platelets from TMEV-infected mice by injecting them with platelet-specific antibodies. The platelet-depleted mice had significantly fewer viral antigen-positive cells in the CNS. Platelet depletion reduced the severities of TMEV-IDD and myocarditis, although the pathology scores did not reach statistical significance. Immunologically, the platelet-depleted mice had an increase in interferon (IFN)-γ production with a higher anti-TMEV IgG2a/IgG1 ratio. Thus, platelets may play roles in TMEV infection, such as gene expression, viral clearance, and anti-viral antibody isotype responses.

PURPOSE:Auto-antibodies (auto-abs) to type I interferons (IFNs) have been identified in patients with life-threatening coronavirus disease 2019 (COVID-19), suggesting that the presence of auto-abs may be a risk factor for disease severity. We therefore investigated the mechanism underlying COVID-19 exacerbation induced by auto-abs to type I IFNs. METHODS:We evaluated plasma from 123 patients with COVID-19 to measure auto-abs to type I IFNs. We performed single-cell RNA sequencing (scRNA-seq) of peripheral blood mononuclear cells from the patients with auto-abs and conducted epitope mapping of the auto-abs. RESULTS:Three of 19 severe and 4 of 42 critical COVID-19 patients had neutralizing auto-abs to type I IFNs. Patients with auto-abs to type I IFNs showed no characteristic clinical features. scRNA-seq from 38 patients with COVID-19 revealed that IFN signaling in conventional dendritic cells and canonical monocytes was attenuated, and SARS-CoV-2-specific BCR repertoires were decreased in patients with auto-abs. Furthermore, auto-abs to IFN-α2 from COVID-19 patients with auto-abs recognized characteristic epitopes of IFN-α2, which binds to the receptor. CONCLUSION:Auto-abs to type I IFN found in COVID-19 patients inhibited IFN signaling in dendritic cells and monocytes by blocking the binding of type I IFN to its receptor. The failure to properly induce production of an antibody to SARS-CoV-2 may be a causative factor of COVID-19 severity.

To meet the energetic requirements associated with activation, proliferation, and survival, T cells switch their metabolic signatures from energetically quiescent to activated. However, little is known about the role of metabolic pathway controlling the development of invariant natural killer T (iNKT) cells. In the present study, we found that acetyl-CoA carboxylase 1 (ACC1), a rate-limiting enzyme for the fatty acid biosynthesis pathway, plays an essential role in the development of iNKT cells in the thymus. Mice lacking T-cell specific ACC1 showed a reduced number of iNKT cells with an increased proportion of iNKT cells at immature stages 0 and 1. Furthermore, mixed bone marrow (BM) chimera experiments revealed that T-cell intrinsic ACC1 expression was selectively important for the development of thymic iNKT cells, especially for the differentiation of the NKT1 cell subset. Our single-cell RNA-sequencing (scRNA-seq) data and functional analysis demonstrated that ACC1 is responsible for survival of developing iNKT cells. Thus, these findings highlighted a novel role of ACC1 in controlling thymic iNKT cell development mediated by the control of cell survival.

Allergic diseases arise from a complex interplay between immune system and environmental factors. A link between the pathogenesis of allergic diseases and type 2 immune responses has become evident, with conventional and pathogenic type 2 helper T (Th2) cells involved in both. Recently, there has been a significant development in therapeutic agents for allergic diseases: IL-5 and IL-5 receptor antagonists, Janus kinase (JAK) inhibitors, and sublingual immunotherapy (SLIT). Mepolizumab, an IL-5, and Benralizumab, an IL-5 receptor antagonist, modulate eosinophilic inflammation mediated by IL-5-producing Th2 cells. Delgocitinib shows that JAK-associated signaling is essential for the inflammatory reaction in atopic dermatitis, one of the common allergic diseases. SLIT has a significant effect on allergic rhinitis by reducing pathogenic Th2 cell numbers. More recently, novel molecules that are involved in pathogenic Th2 cell-mediated allergic diseases have been identified. These include calcitonin gene-related peptide (CGRP), reactive oxygen species (ROS) scavenging machinery regulated by the Txnip-Nrf2-Blvrb axis, and myosin light chain 9 (Myl9), which interacts with CD69. This review provides an updated view of the recent research on treatment of allergic diseases and their cause: conventional and pathogenic Th2 cells.

Introduction Kawasaki disease (KD) is an acute systemic vasculitis that predominantly afflicts children. KD development is known to be associated with an aberrant immune response and abnormal platelet activation, however its etiology is still largely unknown. Myosin light chain 9 (Myl9) is known to regulate cellular contractility of both non-muscle and smooth muscle cells, and can be released from platelets, whereas any relations of Myl9 expression to KD vasculitis have not been examined. Methods Plasma Myl9 concentrations in KD patients and children with febrile illness were measured and associated with KD clinical course and prognosis. Myl9 release from platelets in KD patients was also evaluated in vitro. Myl9 expression was determined in coronary arteries from Lactobacillus casei cell wall extract (LCWE)-injected mice that develop experimental KD vasculitis, as well as in cardiac tissues obtained at autopsy from KD patients. Results and discussion Plasma Myl9 levels were significantly higher in KD patients during the acute phase compared with healthy controls or patients with other febrile illnesses, declined following IVIG therapy in IVIG-responders but not in non-responders. In vitro, platelets from KD patients released Myl9 independently of thrombin stimulation. In the LCWE-injected mice, Myl9 was detected in cardiac tissue at an early stage before inflammatory cell infiltration was observed. In tissues obtained at autopsy from KD patients, the highest Myl9 expression was observed in thrombi during the acute phase and in the intima and adventitia of coronary arteries during the chronic phase. Thus, our studies show that Myl9 expression is significantly increased during KD vasculitis and that Myl9 levels may be a useful biomarker to estimate inflammation and IVIG responsiveness to KD.

AbstractTumor-specific CD8+ T cells play a pivotal role in antitumor immunity and are a key target of immunotherapeutic approaches. Intratumoral CD8+ T cells are heterogeneous; Tcf1+ stemlike CD8+ T cells give rise to their cytotoxic progeny—Tim-3+ terminally differentiated CD8+ T cells. However, where and how this differentiation process occurs has not been elucidated. We herein show that terminally differentiated CD8+ T cells can be generated within tumor-draining lymph nodes (TDLN) and that CD69 expression on tumor-specific CD8+ T cells controls its differentiation process through regulating the expression of the transcription factor TOX. In TDLNs, CD69 deficiency diminished TOX expression in tumor-specific CD8+ T cells, and consequently promoted generation of functional terminally differentiated CD8+ T cells. Anti-CD69 administration promoted the generation of terminally differentiated CD8+ T cells, and the combined use of anti-CD69 and anti–programmed cell death protein 1 (PD-1) showed an efficient antitumor effect. Thus, CD69 is an attractive target for cancer immunotherapy that synergizes with immune checkpoint blockade.