Journal of immunology最新文献

Blood coagulation and immune responses have long been considered as discrete processes. However, recent studies have revealed that mammalian platelets play a critical role in immune regulation in addition to their well-established role in hemostasis. This dual functionality suggests an evolutionary link between platelets and invertebrate blood cells that contributes to both immune responses and wound healing. However, megakaryocytes, the precursor cells of platelets, are unique to mammals. It is widely believed that invertebrates lack a mechanism for producing anucleate cell fragments similar to platelets. Here, we report the discovery of anucleate cell fragments in the coelomic fluid of the sea star Patiria pectinifera. Detailed scanning electron microscopy revealed that the anucleate cell fragments exhibit both morphological and functional similarities to mammalian platelets. These cell fragments, which are derived from immune cells (coelomocytes), accumulate at wound sites, aggregate with coelomocytes, and serve as major sources of extracellular vesicles. Furthermore, extracellular vesicles released by these fragments not only promote aggregate formation in response to foreign substances but also transfer their contents into coelomocytic cytoplasm. Our findings suggest that a mechanism for generating anucleate cell fragments with platelet-like functions already exists in invertebrate immune cells. This study provides new insights into the evolutionary origins and broader immunological significance of platelets.

Dendritic cells (DCs) and B lymphocytes produce major histocompatibility complex class II molecules (MHCIIs) in large amounts to maximize the display of peptides and fulfill their antigen-presentation functions. The surface expression of MHCIIs in these cells is regulated via the ubiquitination of a single conserved lysine residue in the cytoplasmic tail of all known β-chains. This modification is carried out mainly by the MARCH1 E3 ubiquitin ligase. In MARCH1-deficient DCs, the lack of MHCII ubiquitination results in its excessive accumulation at the plasma membrane, disorganizing lipid rafts and tetraspanin webs. These membrane structures regulate numerous biological processes, allowing the interactions between signaling molecules, such as the B-cell receptor (BCR) and CD19. Nevertheless, the full impact of MARCH1 and the ubiquitin-dependent MHCII turnover on the development, activation, and functions of B cells remains to be explored. Here, we show that the absence of MHCII ubiquitination negatively affected the marginal zone (MZ) B-cell pool in mice. We provide evidence that this alteration of B-cell responses may, at least in part, be due to the proteotoxicity of MHCIIs on the CD81-containing tetraspanin web, which impacted the surface dynamics of CD19 and its capacity to activate the PI3K/Akt cascade during tonic BCR signaling. The reduced MZ B-cell pool impaired the immune response to a type 2 T-independent antigen. Interestingly, the germinal center (GC) response against a T-dependent antigen was also negatively affected. Altogether, our results demonstrate the importance of the ubiquitin-dependent control of MHCII proteostasis for B-cell functions.

Influenza is a significant public health and economic threat around the world. Although pneumonia is the most common complication associated with influenza, there are several clinical reports showing an increased risk for cardiovascular disease. Studies have shown that influenza infection correlates with increased incidence of myocardial infarction. Atherosclerosis is a common cause of coronary artery disease including myocardial infarction, stroke, and heart failure. Here, we analyzed the effect of influenza infection in high-fat diet-induced atherosclerosis in Apoe-/- mice. We found increased weight loss and decreased survival, increased numbers of CD11b+Ly6C+ cells (inflammatory monocytes) and CD11b+Ly6G+ cells (neutrophils), increased levels of CCL3, CCL4, and CCL5, increased lung pathology, and increased atherosclerotic lesions in the aorta in influenza-infected Apoe-/- mice when compared to influenza-infected wild-type (WT) and control (PBS-treated) Apoe-/- mice. An increased percentage of RORγt+ and IL-17+ cells were identified in influenza-infected Apoe-/- mice compared with influenza-infected WT mice and PBS-treated Apoe-/- mice. Bone marrow macrophages from influenza-infected Apoe-/- mice showed increased expression of Th17 polarizing cytokines. Influenza-infected Color-flu (Venus)-positive cells were identified in inflammatory monocytes and neutrophils in the lungs, spleen, blood, aorta, and vascular endothelial cells. These results suggest that influenza infection increases arterial inflammation by directly infecting endothelial cells, and indirectly through recruitment of inflammatory monocytes and neutrophils. Increased Th17 responses in influenza-infected Apoe-/- mice may be a possible mechanism involved in increased lung pathology and exacerbation of high-fat diet-induced atherosclerosis.

Tristetraprolin (TTP) is an anti-inflammatory protein that mediates messenger RNA (mRNA) decay of certain transcripts, especially those encoding proinflammatory cytokines. TTP modulates various pathological outcomes in diverse inflammatory diseases; however, its role in ozone (O3)-induced acute lung injury (ALI) has never been tested. Here, we hypothesized that the loss of TTP would exacerbate O3-induced ALI and that the systemic overexpression of TTP would mitigate O3-induced ALI. Accordingly, TTP-knockout (TTPKO), airway epithelial cell-specific TTP-deficient (EpiKO), myeloid cell-specific TTP-deficient (MyeKO), and systemic TTP-overexpressing (TTPΔARE) adult male and female mice, along with their respective littermate control TTP-sufficient mice, were exposed to either O3 (3 ppm) or filtered air for 3 h. The endpoints, including bronchoalveolar lavage fluid cellularity, cytokine levels, and histopathological changes, were assessed 21 to 24 h after O3 or filtered air exposure. As compared with the O3-exposed TTP-sufficient mice, the O3-exposed TTPKO and O3-exposed cell-specific TTP-deficient mice exhibited a significant worsening of ALI outcomes (i.e., neutrophil infiltration, cytokine/chemokine production, and lung pathology). The severity of these outcomes was comparatively milder in O3-exposed EpiKO and O3-exposed MyeKO mice than in O3-exposed TTPKO mice. Conversely, the O3-exposed TTPΔARE mice were protected against O3-induced ALI, as indicated by relatively reduced levels of inflammatory cytokines/chemokines, reduced neutrophil infiltration, and mitigated lung pathology. Collectively, our data suggest that TTP is a critical regulator of inflammation in O3-induced ALI. These findings indicate that enhancing TTP expression could be a potential therapeutic strategy for simultaneously targeting multiple inflammatory cytokines in O3-induced ALI and possibly other inflammatory diseases.

Coronin family proteins are involved in various cellular processes, such as actin cytoskeleton reorganization, cell motility, and vesicular trafficking. Coronin-1, encoded by Coro1a, is specifically expressed in immune cells, and its defect causes severe immunodeficiencies. However, the regulatory mechanisms of Coro1a expression in immune cells remain unknown. Here, we aimed to elucidate the regulatory mechanisms of Coro1a expression. A reporter assay revealed that the promoter region alone was insufficient for Coro1a transcription; both the promoter and gene body regions were required. Promoter deletion analysis revealed that the 85-base fragment of the 5'-flanking region is required for Coro1a transcription in RAW264.7 cells. We identified 5 consensus sequences of GC boxes within this region, and the Sp3 transcription factor was found to bind to the GC box 4 most involved in coronin-1 expression. Sp3 binding regulation likely depended on chromatin accessibility. Further, DNase sequencing analysis revealed several open chromatin regions in the gene body region, including introns, in immune cells. Higher levels of active histone modifications, H3K4me3 and H3K27ac, were also detected in the gene body regions. Five ETS-binding sequences existed in introns 1 and 2, and mutations at these sequences decreased Coro1a transcription. Furthermore, active histone modifications at the intronic region were decreased during differentiation of bone marrow-derived macrophages into bone marrow-derived osteoclasts, which was accompanied by a reduction in Coro1a expression. These results demonstrate that Coro1a transcription is regulated by both the promoter and intronic regions, and this dual regulation could be important for Coro1a transcription in immune cells.

Type 1 diabetes (T1D) results from immune-mediated destruction of pancreatic beta cells. B cells serve as critical antigen-presenting cells whose autoreactive specificities drive disease progression. Conversely, IL-10 producing regulatory B cells (Bregs) exert immunosuppressive functions and have been shown to protect against autoimmunity in mouse models of rheumatoid arthritis and multiple sclerosis, where microenvironmental cues promote their differentiation. In particular, signaling through hypoxia-inducible factor 1α (HIF-1α) induces glycolytic flux that supports Breg expansion. Defects in Breg development and function have been identified in both human T1D and the non-obese diabetic (NOD) mouse, but whether these impairments reflect intrinsic B-cell abnormalities or microenvironmental changes associated with hyperglycemia and inflammation remains unclear. Moreover, the mechanisms by which B cells suppress pathogenic T-cell responses likely vary across disease states. Here, we examine how B cell differentiation, metabolism, and HIF-1α signaling interact to shape immune regulation in autoimmune diabetes. We show that B cells undergo dynamic metabolic remodeling during disease progression. B cells from NOD mice are characterized by exaggerated glucose uptake and elevated IL-10 expression compared with non-autoimmune B6 B cells, despite reduced HIF-1α levels and attenuated induction of HIF-dependent glycolytic genes. These findings indicate that HIF-1α plays a diminished role in controlling IL-10 production in NOD B cells and that IL-10 alone is insufficient to maintain immune tolerance. Together, our results highlight how genetic and microenvironmental factors reprogram B cell metabolism and underscore the need to explore IL-10 independent pathways and B-cell extrinsic mechanisms when developing immunomodulatory therapies for T1D.

Previous studies have reported that African swine fever virus (ASFV) infection can induce inflammatory responses through the activation of the NLRP3 inflammasome, resulting in the release of IL-1β and the cleavage of gasdermin D. However, the mechanism by which pattern recognition receptors in target cells recognize ASFV genomic DNA (gDNA) to activate the NLRP3 inflammasome remains unclear. In this study, we demonstrate that ASFV infection and the transfection of ASFV gDNA can trigger NLRP3-dependent inflammasome activation. Additionally, vimentin was identified as a binding partner for viral gDNA and was found to interact with NLRP3, playing a role in the activation of the NLRP3 inflammasome. Furthermore, we discovered that the knockdown of endogenous vimentin expression inhibited NLRP3 inflammasome activation, leading to a reduction in caspase-1 activation and IL-1β secretion in ASFV-infected or viral DNA-stimulated porcine alveolar macrophages. Our findings reveal a mechanism involving the interaction between vimentin and viral gDNA that mediates the activation of the NLRP3 inflammasome during ASFV infection.

The SARS-CoV-2 pandemic underscored the need for innovative approaches to study humoral immunity and isolate monoclonal antibodies (mAbs) with diagnostic and therapeutic potential. Current methods for repertoire analysis at the clonal level require large-scale recombinant mAb production, limiting accessibility and delaying functional insight. We developed a single-cell culture (SCC) platform that enables profiling of human memory B cells and direct recovery of functional mAbs. Using samples from COVID-19 convalescent and vaccinated donors, we optimized SCCs with NB21 feeder cells, R848, and IL-2, achieving efficient clonal expansion and antibody secretion in short-term cultures. Screening and pseudovirus neutralization assays were performed directly with culture supernatants, bypassing the need for early recombinant antibody production. Antigen-baited cytometry sorting enriched spike-specific memory B cells by ∼30-fold. Among 592 isolated mAbs, 53% bound the Wuhan spike, targeting the receptor-binding domain (28%), N-terminal domain (15%), or other regions (57%). Cross-reactivity analysis revealed that 40% of anti-spike mAbs recognized all tested variants of concern. VH/VL sequencing uncovered convergent rearrangements, including public V3-30 and V3-53/V3-66 clones, consistent with global findings. Two public receptor-binding domain-specific antibodies demonstrated broad neutralization when produced recombinantly. Together, these results validate the SCC system as a streamlined approach for unbiased repertoire analysis and functional mAb isolation. More broadly, the platform provides a practical framework for linking B cell clonal composition with antigen specificity and serum antibody responses. By reducing costs and simplifying workflows, it expands opportunities for antibody discovery and immunoepidemiological studies, fostering wider global participation in therapeutic antibody research.

The innate immune system of teleost fish, such as Takifugu obscurus, depends on pattern recognition receptors to detect microbes and mount immune responses. In this study, a new collectin gene was identified in T. obscurus, designated ToCL-11. The full-length cDNA of ToCL-11 encodes a 266-amino acid protein featuring a signal peptide, a collagen-like domain, and a carbohydrate-recognition domain (CRD). Subcellular localization analysis revealed that ToCL-11 is secreted and undergoes pathogen-specific redistribution upon bacterial stimulation. Expression of ToCL-11 was highest in immune tissues (liver, intestine, and kidney) and was upregulated following bacterial challenge. Recombinant ToCL-11 (rToCL-11) and its CRD (rToCL-11-CRD) exhibited broad-spectrum antibacterial activities, including bacterial binding, agglutination, growth inhibition, and biofilm suppression, with rToCL-11 showing stronger activity. rToCL-11 was also found to interact with recombinant calreticulin (rToCRT) via its collagen domain (rToCL-11-Collagen). RNAi-mediated knockdown of ToCRT and ToCL-11 suppressed nuclear translocation of nuclear factor-kappa B (ToNF-κB), leading to reduced expression of pro-inflammatory cytokines, including interleukin-1β (ToIL-1β), ToIL-6, ToIL-8, and tumor necrosis factor-α (ToTNF-α), and impaired bacterial clearance. Luciferase reporter assays and in vivo studies confirmed that TomiR-194b-3p directly targets ToCL-11 and acts as a negative regulator. Overexpression of TomiR-194b-3p downregulated ToCL-11, inhibited ToNF-κB nuclear translocation, and suppressed cytokine expression, whereas its knockdown elicited opposite effects. These results elucidate the immune regulatory function of ToCL-11 and its modulation by TomiR-194b-3p, underscoring their potential as therapeutic targets for enhancing immunity in aquaculture.

B cells play critical roles in humoral immunity to infection, vaccination, and autoimmunity. The differentiation of B cells into antibody-producing plasma cells (PCs) has been extensively studied, but the role of metabolic transporters that mediate nutrient uptake during PC differentiation is not well-understood. Here, we characterized the dependence of B cells and PC differentiation on the neutral amino acid transporter SLC7A5. We demonstrate that SLC7A5 promotes B cell functions including proliferation and PC differentiation in vitro and in vivo after immunization with T dependent and independent antigens. Deletion of SLC7A5 in B cells suppressed the function of mTORC1 and enforced mTORC1 activity rescued PC differentiation. The role of SLC7A5 in B cells appears to be unrelated to leucine uptake because B cells were insensitive to extracellular leucine depletion. Defects in SLC7A5-deficient B cells could, however, be rescued by extracellular methionine supplementation, suggesting a role for methionine in SLC7A5-dependent B cell function and PC differentiation. Our study provides evidence for a leucine-independent role of SLC7A5 in B cell function and PC differentiation.