Abstract Long-lived plasma cells have traditionally been viewed through the lens of bone marrow-resident IgG-secreting cells that maintain systemic serological memory. However, recent timestamping approaches and isotype-specific analyses have revealed diverse trajectories toward plasma-cell longevity. Plasma-cell longevity is not specified at a single developmental checkpoint, but emerges through a multi-step process involving the timing and site of plasma-cell generation, migratory competence, entry into and adaptation to tissue niches, and progressive maturation. Moreover, emerging studies of non-IgG plasma cells indicate that distinct antibody isotypes use different anatomical and molecular strategies to sustain antibody production. In particular, the recent identification of IgE long-lived plasma cells in secondary lymphoid tissues suggests that the bone marrow is not the only anatomical site capable of supporting durable plasma-cell survival. Together, these findings argue against a single, universal model of plasma-cell longevity and instead support a framework in which antibody persistence is achieved through isotype-specific and tissue-specific logic.
Recent pandemics, the increasing incidence of cancer and an inversion of the age pyramid towards an older society fuels the need for an in depth understanding of the field of inflammaging and changes in the immune system, in particular of the T cell compartment, which is the most impacted during ageing. Starting from quantitative and qualitative changes that occur in T cells during ageing, this review discusses pathophysiological factors that lead to or accelerate these processes. Furthermore, it highlights emerging strategies aimed at overcoming age-related T-cell dysfunction, with a focus on recent advances in the field. Together, these insights may contribute to a better understanding of how healthy ageing can be promoted through the preservation or rejuvenation of T-cell "youthfulness", which is central for healthy ageing.
Primary sclerosing cholangitis (PSC) is a chronic autoimmune cholestatic liver disease characterized by progressive inflammation and fibrosis, but the role of neutrophils in PSC remains poorly understood. To define neutrophil states in the PSC liver microenvironment, we performed single-cell RNA sequencing of leukocytes isolated from liver perfusate obtained from healthy donor grafts and explanted PSC livers. We identified a marked expansion of transcriptionally diverse neutrophil subclusters in PSC liver perfusate. Importantly, PSC livers were enriched for four neutrophil subclusters: RHOB-high, immediate early gene-high, heat shock protein-high, and CXCL8-high liver neutrophil-like subclusters. These PSC-associated neutrophil subclusters showed increased activity of the TNF and IL-17 signaling pathways, consistent with current views of PSC pathogenesis. They also displayed activation of inflammatory transcriptional regulators, including CEBPB, JUN, FOS, and RELA. Pseudotime analysis suggested that RHOB and immediate early gene subsets were derived from immature neutrophils, whereas liver neutrophil-like and heat shock protein-high subsets exhibited more mature and tissue-adapted features. Together, these data reveal previously unrecognized heterogeneity of liver neutrophils in PSC and identify inflammatory neutrophil programs that may contribute to sustained hepatic inflammation and represent potential therapeutic targets.
Vaccine reactogenicity refers to the capacity of a vaccine to induce transient local and systemic adverse reactions (ARs). Although these ARs are often attributed to vaccine-induced innate inflammation, accumulating evidence indicates that the inflammatory pathways causing symptoms are not necessarily identical to those required for protective immunity. mRNA-lipid nanoparticle (LNP) vaccines provide a valuable framework for examining this relationship, because both the mRNA cargo and the LNP delivery system can contribute to innate immune activation. Early inflammatory responses following mRNA-LNP vaccination appear to reflect the interplay of multiple signals, including ionizable lipid-driven signaling, mRNA-associated interferon (IFN) responses, endosomal membrane perturbation, and tissue-derived danger signals. These upstream events can be amplified through cytokine networks that promote systemic symptoms. Interleukin-1 (IL-1) has emerged as a major contributor to this process, although IL-6, tumor necrosis factor-alpha (TNF-α), type I IFN, and prostaglandin-related pathways also contribute, depending on the experimental model and context. In this review, we summarize recent evidence linking upstream sensing pathways to local and systemic ARs, and discuss how these pathways intersect with vaccine-induced adaptive immunity. We also consider booster-associated amplification of ARs as an example in which immune memory may reshape innate cytokine responses after repeated vaccination. Understanding these relationships will help delineate the shared and distinct inflammatory circuits underlying ARs and protective immunity. These mechanistic insights may also inform the rational design of low-reactogenic mRNA-LNP formulations that retain sufficient immunogenicity.
Humans possess various blood cell types, such as T cells, B cells, monocytes/macrophages, neutrophils, dendritic cells, erythrocytes, and platelets/thrombocytes, and these lineages are shared by nearly all vertebrates. Although invertebrates such as tunicates, sea urchins, flies, and sponges possess different blood cell lineages, some homology exists between vertebrate and invertebrate blood cells. Comparing cell lineages between different species can help estimate the evolution of blood cell lineages and immune systems across more than 600 million years of animal history. Studies on blood cells in vertebrate and invertebrate species have put some mile stones in the roads of blood cell evolution, but a comprehensive map has not been drawn. Recent advances in sequencing and bioinformatic technologies and the accumulation of genomic information for various animal species enabled us to develop an analytical method to compare cell lineages between far different species. Our recent work suggested one probable evolutionary history of blood cell lineages, in which T cells, NK cells, ILC, mast cells, erythrocytes, and thrombocytes evolved from prototypic mast cells. In addition, a vestige of this history was detected in our body as a linage restriction process in blood cell differentiation. Thus, studying evolution can help clarify current biological systems, and vice versa.
Aging is the primary risk factor for a wide spectrum of chronic diseases, ranging from infectious diseases and cancer to autoimmunity and neurodegeneration. One of the key drivers of this increased susceptibility is the progressive decline in immune function-immunosenescence that reshapes the host's inflammatory landscape. Emerging evidence points to an age-associated expansion of cytotoxic CD4+ T cells (CD4 CTLs), which can play context-dependent protective or pathogenic roles in host homeostasis and disease, reflecting their unique integration of helper and cytotoxic programs as well as their preferential expansion during aging. On the protective side, CD4 CTLs contribute to immune surveillance and host defense against viral infections and malignancies. Conversely, in selected settings, they can function as pathogenic effectors in autoimmune and neurodegenerative disorders. In this review, we synthesize the emerging biology of CD4 CTLs, highlighting their differentiation and dual roles in protection and pathology. Beyond a descriptive overview, we propose a conceptual framework that places age-associated CD4 CTL expansion at the intersection of aging and age-associated disease. Rather than viewing late-life pathologies as fully independent events, we suggest that at least a subset may be partially interconnected by recurrent CD4 CTL programs, while emphasizing that the strength of evidence and the degree of causality differ substantially by disease context. This framework provides a basis for asking when CD4 CTLs should be enhanced, restrained, or more precisely redirected to promote healthy longevity.
Regulatory T cells (Tregs) play an essential role in maintaining immune tolerance and controlling excessive inflammation. Although traditionally viewed as a stable lineage dedicated to broad immunosuppression, accumulating evidence has revealed that Tregs exhibit remarkable heterogeneity and functional adaptability, allowing them to undergo specialization in response to local inflammatory environments. Among these specialized subsets, Th1-type Tregs (Th1-Tregs), characterized by the co-expression of Foxp3 and the transcription factor T-bet, have emerged as key regulators of type 1 immune responses. By expressing the chemokine receptor CXCR3, these cells localize to IFN-γ-rich inflammatory sites and selectively modulate Th1-driven immune circuits. Recent studies have demonstrated that Th1-Tregs play context-dependent roles across diverse pathological conditions. In the tumor microenvironment, they suppress cytotoxic immunity and contribute to tumor immune evasion. In contrast, during autoimmune diseases and acute infections, Th1-adapted regulatory programs protect host tissues by restraining excessive inflammation. These findings highlight how regulatory T cells dynamically adapt to local inflammatory environments to control type 1 immune responses in different tissues. In this review, we summarize the molecular mechanisms underlying Th1-Treg differentiation and discuss how these specialized regulatory programs shape immune responses across different disease contexts.
Psmb11-encoded β5t is a proteolytic subunit of thymoproteasomes expressed in cortical thymic epithelial cells (cTECs). β5t-containing thymoproteasomes are essential for the thymic generation of CD8-lineage cytotoxic T cells. Here, we outline the current understanding of the mechanisms underlying thymoproteasome-dependent CD8 T cell development. We focus on the cTEC-specific expression of β5t, highlighting its unique expression in comparison with the transcription factor Foxn1, which is expressed in both thymic and skin epithelial cells. Additionally, we discuss our recent engineering of monoclonal antibodies that are specific for mouse and human β5t. β5t not only provides an important machinery for CD8 T cell development but also serves as a valuable tool for further study of the biology of thymic epithelial cells in health and disease.
This review summarizes key topics discussed in the session "Biology within the Thymus" at the 54th Annual Meeting of the Japanese Society for Immunology, which highlighted recent advances in our understanding of T-cell development and fate determination. In particular, the session focused on transcriptional regulation of T-lineage commitment and the mechanisms by which T-cell receptor (SP) signaling governs thymocyte differentiation. Early T-lineage commitment is established through the integration of thymic microenvironmental cues and intrinsic transcription factors, including Bcl11b, PU.1, and Runx family proteins. Among these, Runx transcription factors play essential roles throughout thymocyte development, not primarily through changes in expression but through dynamic regulation of their molecular interactions and genomic occupancy. Following commitment, αβTCR-expressing CD4+CD8+ double-positive (DP) thymocytes undergo MHC-dependent selection and differentiate into CD4+ helper or CD8+ cytotoxic T cells. Although the core components of proximal TCR signaling are largely shared, accumulating observations suggest that qualitative and quantitative differences in signaling-shaped by signal strength, duration, and subcellular context-may contribute to lineage specification. In this regard, recent studies discussed in this session highlighted the role of co-receptor-free Lck as an active signaling pool capable of initiating TCR signaling independently of CD4 or CD8 association, thereby adding an additional layer of complexity to MHC-dependent thymic selection. In addition, post-translational modification of Runx proteins, particularly within the conserved WRPY motif, has emerged as a molecular link between proximal TCR signaling mediated by kinases such as Lck and lineage-specific transcriptional repression. Together with advances in thymic culture systems, genome editing, and proteomic approaches, these findings underscore the tight coupling between proximal TCR signaling-including both co-receptor-dependent and co-receptor-independent Lck activity-and transcriptional regulation, and highlight Runx transcription factors as key integrators that translate MHC-specific TCR signals into transcriptional programs determining thymocyte fate.
Group 2 innate lymphoid cells (ILC2s) play critical roles in type 2 airway inflammation. 17,18-epoxyeicosatetraenoic acid (17,18-EpETE), an eicosapentaenoic acid metabolite, is generated from dietary omega-3 fatty acids, and may have anti-inflammatory activities. We evaluated the effect of 17,18-EpETE and its metabolite, 17,18-dihydroxy-eicosa-5,8,11,14-tetraenoic acid (17,18-diHETE), on IL-33-induced airway inflammation involving ILC2s. We evaluated the in vitro effects of 17,18-EpETE and 17,18-diHETE on the IL-33-induced production of IL-5 and IL-13 by human ILC2s (isolated from peripheral blood) using ELISA. Expression of the corresponding fatty acid receptors and the GATA-3 transcription factor were examined using flow cytometry and quantitative RT-PCR. Additionally, we examined the in vivo effects of 17,18-EpETE or 17,18-diHETE in a mouse model of type 2 airway inflammation induced by intranasal (i.n.) instillation of IL-33. 17,18-EpETE or 17,18-diHETE inhibited IL-33-induced production of IL-5 and IL-13, and IL-33-induced expression of GATA-3 in human ILC2s. GW1100, an antagonist of G protein-coupled receptor (GPR) 40, or GW9662, an antagonist of peroxisome proliferator-activated receptor γ (PPARγ), counteracted the inhibitory effects of 17,18-EpETE or 17,18-diHETE on the IL-33-induced production of IL-5 and IL-13 by ILC2s. I.n. administration of 17,18-EpETE or 17,18-diHETE attenuated IL-33-induced eosinophil infiltration and mucus production in mouse nasal mucosa, and production of IL-5 and IL-13 in lung tissue and bronchoalveolar lavage fluid. The present study demonstrated the anti-inflammatory effects of 17,18-EpETE and 17,18-diHETE on IL-33-induced airway inflammation involving ILC2s. I.n. administration of 17,18-EpETE may be a new therapeutic approach for the treatment of intractable type 2 airway inflammation.
The IgM Fc receptor (FcμR), the sole receptor specific for IgM, is crucial for B cell survival and humoral immunity. Yet, its role in memory B cells (MBCs) has remained unclear. Here, we show that FcμR-/- mice immunized with the T-dependent antigen 4-hydroxy-3-nitrophenyl acetyl-chicken γ-globulin (NP-CGG) generate normal numbers of IgG1+ MBCs with long-term survival comparable to that of WT mice. However, the IgG1+ MBCs in FcμR-/- mice contained a reduced proportion of mature CD80+PD-L2+ cells, a subset associated with potent recall responses and plasma cell differentiation. Consistently, adoptive transfer of NP-specific MBCs and CGG-specific memory T cells into Rag1-/- mice revealed significantly diminished memory B cell responses in recipients of FcμR-/- MBCs. Mechanistically, FcμR-/- IgG1+ MBCs exhibited impaired B cell receptor signaling and reduced activation of transcription factors essential for plasma cell differentiation upon antigen re-challenge both in vivo and in vitro. Together, these findings establish FcμR as a previously unrecognized key regulator of CD80+PD-L2+ MBC formation and recall responses.
The tumor microenvironment (TME) is a complex landscape where metabolic interactions significantly dictate antitumor immunity. Immune evasion in cancer is typically discussed in terms of inhibitory receptors and ligands, suppressive cytokines, defective antigen presentation, and metabolic competition. However, recent evidence reveals that intercellular mitochondrial transfer adds a new mechanism of immune evasion in the TME. The mitochondrial fitness of T cells is central to sustained effector function, memory formation, and responsiveness to immune checkpoint blockade. Tumor cells can act as pathogenic mitochondrial donors, transferring functional or dysfunctional mitochondria to neighboring T cells via tunneling nanotubes and extracellular vesicles. This process involves a mitophagy imbalance that leads to the homoplasmic replacement of endogenous mitochondria, thereby driving T-cell senescence, impairing memory formation and long-term antitumor function, and ultimately weakening cancer immunosurveillance. Overall, mitochondrial transfer should be considered a new part of the tumor immune evasion framework. It also provides new therapeutic opportunities for improving cancer immunotherapy.
Neutrophils and eosinophils have long been regarded as terminal effectors of innate immunity. Technical advances in single-cell RNA sequencing define transcriptome-based granulocyte subsets beyond classical density- and surface marker-based classifications. These approaches reveal substantial heterogeneity in granulocyte differentiation states, activation programs, and tissue adaptation across human diseases. In microscopic polyangiitis, type II interferon pathways shape a pathogenic neutrophil activation state, and serum IFNγ levels at disease onset may serve as a potential biomarker for subsequent relapse. In infectious diseases, including COVID-19 and sepsis, the expansion of immunosuppressive ARG1- and IL1R2-expressing neutrophils is reported in severe disease and may reflect altered immune responses. MMP9-high neutrophils are enriched in cardiovascular disorders and may be linked to thrombosis and ischemic injury. In allergic diseases, spatial and single-cell analyses identify tissue-specific eosinophil states and their interactions with epithelial and macrophage compartments, highlighting context-dependent eosinophil activation within inflamed tissues. Despite emerging evidence for disease-associated granulocyte heterogeneity, whether these populations causally contribute to disease pathophysiology remains largely unclear. Experimentally validated functions and clinically applicable surrogate markers, such as surface markers or circulating proteins, are still needed. This review summarizes recent advances and current limitations in understanding granulocyte heterogeneity across immune-mediated and inflammatory diseases, and discusses how integrative single-cell approaches may support the development of clinically relevant biomarkers and targeted therapeutic strategies.
How tissue damage cues and regulated cell death programs instruct antigen-specific mucosal IgA after vaccination remains incompletely defined. Using a mouse model of intranasal whole-virion inactivated influenza vaccination, we identify two proximal inputs that shape antibody output and virologic control: epithelial necroptosis-associated interleukin-33 release and a macrophage death-program switch that unmasks interleukin-1α. Immunization was accompanied by lung cell death, interleukin-33 release, and the induction of antigen-specific mucosal immunoglobulin A. In alveolar macrophages, vaccine uptake required phagocytosis and was associated with lysosomal destabilization and cathepsin B activity, which were linked to interleukin-1α release under conditions that favored regulated necrotic cell death. Consistent with this, pharmacologic inhibition of caspases shifted the dominant death program in alveolar macrophages and was associated with enhanced B cell activation in the cervical lymph nodes and increased immunoglobulin A-producing cell-like populations. At the functional level, caspase inhibition augmented vaccine-elicited protection, including reduced lung viral titers and attenuated pathology after homologous challenge and improved control of a within-subtype drift influenza A virus challenge strain; these enhancements were partly dependent on interleukin-1α. Together, these data support a model in which alarmin cues and regulated cell death pathways in the lung modulate the magnitude of mucosal immunoglobulin A responses and contribute to virologic control after intranasal whole-virion inactivated influenza vaccination. Limitations include reliance on pharmacologic pathway modulation and a mouse intranasal whole-virion inactivated influenza vaccine model; thus, mechanistic generalization beyond this context should be made cautiously.
Recent studies identified that the dysregulation of fibroblast activity, in addition to impairment in epithelial integrity and uncontrolled immune response, is implicated in the pathogenesis of inflammatory bowel disease (IBD). The anti-inflammatory cytokine IL-10 and its receptors IL-10Rα and IL-10Rβ have IBD-associated single nucleotide polymorphisms. In the intestine, IL-10 signaling is essential for maintaining an anti-inflammatory state of myeloid cells and inducing regulatory T cells, thereby preventing intestinal inflammation linked to IBD development. However, its impact on the physiology and pathophysiology of intestinal fibroblasts is poorly understood. Here, we show that Il10ra deficiency leads to increased expression of a subset of genes in colonic fibroblasts, most of which are associated with the type I interferon (IFN) and type II IFN signaling pathways. In addition, Pdgfra-cre; Il10raf/f mice aged 16 weeks or older develop chronic spontaneous colitis and subsequent fibrosis accompanied by enhanced infiltration of myeloid cells and effector CD4+ T cells in the lamina propria of the colon. Moreover, Pdgfra-cre; Il10raf/f mice at 12 weeks of age exhibit more severe clinical symptoms than those of Il10raf/f mice during dextran sodium sulfate-induced colitis that can be suppressed by the administration of anti-IFNAR1 antibody but not anti-IFNGR1 antibody. Therefore, inhibition of type I IFN pathway via IL-10Rα signaling in fibroblasts is one of the IL-10-dependent mechanisms underlying the prevention of large intestinal pathology.
Several regulatory B-cell (Breg) subsets have been implicated in autoimmune diseases. We investigated Breg subsets in non-infectious uveitis (NIU) and in mouse models of experimental autoimmune uveitis (EAU). Blood samples from NIU patients with active disease (n = 13), in remission (n = 37) and healthy controls (n = 10) were immunophenotyped for CD19(+)CD24(hi)CD38(lo) memory B cells, CD19(+)CD24(hi)CD38(hi)-immature Bregs (iBregs), and CD19(+)CD38(int)CD24(int)-mature Bregs. In NIU, levels of peripheral blood iBregs and serum interleukin-10 (IL-10) were decreased in active disease vs. remission (P < .01). In quiescent NIU, iBregs were isolated and, when added at increasing ratios to autologous CD3(+) T cells, downregulated T-cell proliferation. In an EAU model, at peak disease, CD19(+)CD1d(hi)CD5(+) B10, CD19(+)CD5(+) B1, CD19(+)CD21(hi)CD24(hi)CD23(+) transitional two marginal-zone precursor (T2-MZP) and CD19(+)CD21(hi)CD23(-) marginal-zone B (MZB) Breg subsets were analysed both phenotypically and functionally. In EAU spleens, all Breg subsets investigated were detectable, but the IL-10-expressing B10-Breg subset was immunosuppressive and inversely correlated with disease severity (P = .048, R-2 = 0.47). Blood-derived IL-10-expressing B10 and B1 Bregs were increased in both adjuvant controls and EAU but were significantly reduced in clinically milder EAU. In dissociated retinal cells, only the B10-Breg subset was detectable and increased in EAU. Selective Breg subsets may be immunosuppressive, with iBregs in NIU and IL-10-expressing B10 Bregs in EAU.
STAT (signal transducers and activators of transcription) transcription factors are activated by tyrosine phosphorylation after cytokine stimulation and are critical for the differentiation of T-helper (Th) cells into particular Th lineage subsets. How STAT-mediated Th cell differentiation is negatively regulated, however, is not fully understood. Here, we report that PDLIM4 binds to STAT3, 4, and 6 and suppresses gene activation mediated by these STATs. PDLIM4 acts as an adaptor that recruits PTP-BL, a protein tyrosine phosphatase, through its LIM (abnormal cell lineage 11-islet 1-mechanosensory abnormal 3) domain, facilitating dephosphorylation of STAT proteins. PDLIM4-deficiency in CD4+ T cells resulted in augmented tyrosine phosphorylation of these STAT proteins and consequently enhanced Th1, Th2, and Th17 cell differentiation, suggesting that PDLIM4 regulates the differentiation of multiple lineages of Th cells by suppressing STAT signaling. We further found that a non-synonymous single-nucleotide polymorphism in PDLIM4, which causes the substitution of a glycine residue with a cysteine in the LIM domain, is associated with susceptibility to rheumatoid arthritis and Graves' disease, both of which are known to be Th17 cell-driven autoimmune diseases. Notably, PDLIM4 containing this amino acid substitution in the LIM domain showed reduced binding to PTP-BL and was therefore partially impaired in its ability to dephosphorylate STAT3 and suppress STAT3 signaling. Our findings define an essential role of PDLIM4 in negatively regulating STAT-mediated Th-cell differentiation and preventing the onset of human autoimmune diseases.
Pulmonary fibrosis has a poor prognosis because of challenges in early diagnosis and therapeutic intervention. Current treatments remain largely ineffective due to an incomplete understanding of the complex pathology, including the interactions between fibroblasts and profibrotic immune cells within fibrotic lungs. To elucidate the dynamics of fibrosis, we performed single-cell RNA sequencing on bronchoalveolar lavage fluid obtained from patients with interstitial lung disease (ILD). We identified the SPP1- and APOE-expressing macrophage population that is commonly present across ILDs. Histological analysis showed that this macrophage population accumulated at the center of fibrotic foci. Furthermore, the ratio of this macrophage population was increased in both progressive pulmonary fibrosis and idiopathic pulmonary fibrosis. Transcriptomic analysis further divided this macrophage population into two subsets: SLC40A1⁺ or HAMP⁺ fibrosis-associated macrophages. We found that the relative balance of IL-10 and IL-8 regulated SLC40A1 and HAMP expression within fibrosis-associated macrophages. Additionally, histological analysis revealed that bronchial epithelium expressed IL-8, while type II alveolar epithelial cells expressed IL-10 in the fibrotic lung. SLC40A1⁺ fibrosis-associated macrophages localized to CD31⁺ perivascular regions and mediated the uptake and degradation of the hemoglobin-haptoglobin complex. This dual pathway-providing iron via SLC40A1 and intracellular iron accumulation via HAMP-facilitated the transition of fibroblasts into SPP1⁺ myofibroblasts. Moreover, ferroptotic fibroblasts secreted transforming growth factor-beta 1 (TGF-β1), which further contributes to fibrotic progression. In conclusion, aberrant iron metabolism orchestrated by fibrosis-associated macrophages may contribute to fibrosis by facilitating the transition of myofibroblasts. These findings provide mechanistic insight into the progression of autonomous pulmonary fibrosis.
Adaptive immunity is often viewed as a defining innovation of vertebrates, characterized by somatically diversified antigen receptors and clonal lymphocyte lineages. Yet the evolutionary origins of such systems remain incompletely understood. In this review, we examine adaptive immunity from a comparative perspective across Metazoa, focusing on the design principles that link molecular diversification, immune cell differentiation, and proliferative dynamics. We first outline the two adaptive immune architectures found in vertebrates. Jawed vertebrates employ immunoglobulin-based and T-cell receptor-based recognition generated through recombination-activating gene (RAG)-mediated V(D)J recombination, whereas jawless vertebrates assemble variable lymphocyte receptors using cytidine-deaminase-dependent diversification of leucine-rich repeat modules. Despite their distinct molecular entities, these systems converge on shared design principles, including somatic diversification, developmental restriction of genome editing, immune cell differentiation, and specialized microenvironments for immune education. To introduce evolutionarily more ancient systems, several diversification mechanisms of antigen receptors in invertebrates will be subsequently surveyed. These systems generate substantial molecular diversity without canonical clonal selection, suggesting that immune recognition and diversification can be achieved through multiple evolutionary strategies. Particular attention is given to emerging insights into invertebrate immune cell diversification, where single-cell transcriptomics is revealing complex hematopoietic lineages and regulatory programs. These observations suggest that adaptive immunity did not emerge abruptly but rather represents one solution within a broader evolutionary landscape of immune diversification strategies. Understanding how diversification, proliferation, and cellular organization interact across animal lineages will help clarify the fundamental design constraints that shaped the evolution of vertebrate adaptive immune systems.
Moyamoya disease (MMD) is a cerebrovascular disorder that predominantly affects East Asian populations. It is characterized by progressive stenosis or occlusion of terminal internal carotid arteries. Although inflammatory and autoimmune responses have been implicated in MMD pathogenesis, the precise molecular mechanisms underlying the disease remain poorly understood. RNF213, a key susceptibility gene for MMD, has been linked to inflammatory signaling; however, its role in NF-κB-driven inflammation remains unclear. Here, we identify RNF213 as a critical regulator of the IL-6 amplifier (IL6-Amp), a mechanism that enhances NF-κB-mediated inflammation in the presence of IL-6-STAT3 in non-immune cells. RNF213 knockdown reduced IL-6 expression in H4 cells, a model for IL6-Amp induction via tumor necrosis factor (TNF)-α and IL-6 co-stimulation, selectively suppressing NF-κB target genes. In vivo, RNF213 depletion attenuated inflammation in an NF-κB-dependent imiquimod-induced ear swelling model. The MMD-associated RNF213 p.R4810K variant enhanced NF-κB activation by strengthening the interaction between RNF213 and TRAF2, a key adaptor in TNF-α-NF-κB signaling. Consistent with these findings, histopathological analysis of superficial temporal arteries from MMD patients revealed genotype-dependent IL6-Amp activation, with pronounced phosphorylation of NF-κB p65 and STAT3 in homozygous carriers. In contrast, heterozygous and wild-type vessels showed minimal basal activation, but in vitro stimulation of arachnoid cells from a heterozygous patient recapitulated IL6-Amp responsiveness. Collectively, these findings establish RNF213 as a pivotal regulator of NF-κB-driven inflammation and suggest that the p.R4810K variant amplifies inflammatory signaling, thereby contributing to MMD pathogenesis. This study not only advances our understanding of MMD pathophysiology but also highlights potential therapeutic strategies targeting inflammation.
