International Immunology[JOURNAL]
Sun
200 papers
Immune responses underpinning acute co-infections with unrelated viruses: timing and location matter.
Foo IJH, Kedzierski L, Kedzierska K
Int Immunol · 2025 Aug · PMID 40127041 · Full text
Immunity to viral infections is generally studied in isolation by measuring immune responses towards a single virus. However, concurrent or sequential viral co-infections can occur in a single host. Viral co-infections c...
Immunity to viral infections is generally studied in isolation by measuring immune responses towards a single virus. However, concurrent or sequential viral co-infections can occur in a single host. Viral co-infections can impact anti-viral immunity by altering protective responses and driving immunopathology. Understanding immune mechanisms towards co-infections with unrelated viruses is highly relevant to treatment and prevention. There is, however, a paucity of data on immune responses towards viral co-infections, especially with unrelated viruses. Most commonly studied viral co-infections include chronic viruses, such as hepatitis B, hepatitis C, and human immunodeficiency virus, as well as viruses infecting the same tissues, including respiratory viral co-infections. However, the immunological consequences of co-infections with unrelated acute viruses are less understood, especially for viruses affecting different anatomical sites. As co-infecting viruses can have a more pronounced impact on human health compared to infection with a single virus, understanding immune responses and, especially, the impact of timing, sequence, and location of viral co-infections is of key importance. This review provides an overview of the current knowledge on acute viral co-infections with unrelated viruses, underpinning immune mechanisms, and implications for vaccination regimens.
Single-cell multiomic analysis revealed the differentiation, localization, and heterogeneity of IL10+ Foxp3- follicular T cells in humans.
Fujioka S, Fujioka M, Imoto Y … +5 more , Harada Y, Yoshitomi H, Kubo M, Hiraoka Y, Ueno H
Int Immunol · 2025 Jul · PMID 40117325 · Publisher ↗
Germinal center (GC) reactions are tightly regulated to generate high-affinity antibodies. Although IL10+ Foxp3- follicular T cells have recently been described as contributing to the suppression of GC reactions, their d...
Germinal center (GC) reactions are tightly regulated to generate high-affinity antibodies. Although IL10+ Foxp3- follicular T cells have recently been described as contributing to the suppression of GC reactions, their differentiation, localization, and heterogeneity remain incompletely understood. Additionally, it remains unclear whether IL10+ Foxp3- follicular T cells represent a transient status or an independent subset. To address these gaps, we performed integrative single-cell analysis of transcriptomes, epigenomes, surface proteomes, and TCR repertoires in human tonsillar CD4+ T cells. Unbiased clustering revealed IL10+ Foxp3- follicular T cells as a transcriptionally and epigenetically unique subset. This subset exhibited features of both T follicular helper (Tfh) and T regulatory type 1 (Tr1) cells, and accordingly, hereafter, we call them T follicular regulatory type 1 (Tfr1) cells. Analysis using imaging mass cytometry and spatial RNA-TCR sequencing demonstrated their presence within GCs in humans. Bioinformatic analysis suggested that Tfr1 cells differentiate from GC-Tfh cells upon strong TCR stimulation, a finding corroborated by mouse in vivo experiments and time-series single-cell RNA-TCR sequencing of human in vivo CD4+ T cells. Of note, our bioinformatic analysis suggested that Tfr1 cells receive strong TCR signals from ICOS-Lhigh GC-B cells, likely representing high-affinity GC-B cells. Finally, we show that Tfr1 cells acquire a resident memory phenotype following an effector phase. Together, our findings suggest that high-affinity ICOS-Lhigh GC-B cells transform follicular T cells from GC-Tfh cells to Tfr1 cells, which likely become memory cells and reside in the lymphoid organ to support effective antibody production.
Effect of prevaccination blood and T-cell phenotypes on antibody responses to a COVID-19 mRNA vaccine.
Hidaka Y, Jo N, Kikuchi O … +10 more , Fukahori M, Sawada T, Shimazu Y, Yamamoto M, Kometani K, Nagao M, Nakajima TE, Muto M, Morita S, Hamazaki Y
Int Immunol · 2025 Jun · PMID 40110889 · Full text
Despite the high effectiveness of the coronavirus disease 2019 (COVID-19) mRNA vaccines, both immunogenicity and reactogenicity show substantial interindividual variability. One key challenge is predicting high and low r...
Despite the high effectiveness of the coronavirus disease 2019 (COVID-19) mRNA vaccines, both immunogenicity and reactogenicity show substantial interindividual variability. One key challenge is predicting high and low responders using easily measurable parameters. In this study, we performed multivariate linear regression analysis, which allows adjustment for confounding, to explore independent predictive factors for antibody responses. Using data from 216 healthy vaccinated donors aged 23-81 years, we evaluated baseline characteristics, prevaccination blood and T-cell phenotypes, and post-vaccination T-cell responses as variables, with anti-receptor-binding domain (RBD) immunoglobulin G (IgG) titers following two doses of BNT162b2 vaccination as the primary outcome. Consistent with previous reports, higher age, a history of allergic disease, and autoimmune disease were associated with lower peak IgG titers. Additionally, the frequencies of interferon-γ+ spike-specific CD4+ T cells (T-cell response) following the first vaccination strongly correlated with higher IgG responses, while those of pre-existing spike-reactive T cells showed no association with peak IgG titers. Furthermore, we identified lower percentages of naïve CD8+ T cells, lower hemoglobin levels, lower lymphocyte counts, and higher mean corpuscular volume as independent pre-vaccination predictors of lower peak IgG levels. Notably, the frequency of naïve CD8+ T cells showed a positive correlation with the peak IgG levels even in univariate analysis. These findings contribute to the individualized prediction of mRNA vaccine efficacy and may provide insights into the mechanisms underlying individual heterogeneity in immune responses.
Roles of fibroblasts in the pathogenesis of inflammatory bowel diseases and IBD-associated fibrosis.
Ito T, Kayama H
Int Immunol · 2025 Jun · PMID 40110813 · Publisher ↗
Ulcerative colitis and Crohn's disease, the principal forms of inflammatory bowel disease (IBD), are chronic relapsing inflammatory disorders of the gastrointestinal tract. The incidence and prevalence of IBD have been i...
Ulcerative colitis and Crohn's disease, the principal forms of inflammatory bowel disease (IBD), are chronic relapsing inflammatory disorders of the gastrointestinal tract. The incidence and prevalence of IBD have been increasing worldwide, but their etiology remains largely unknown. Although anti-TNF agents can be highly effective in IBD patients, 10%-40% of patients do not respond to primary anti-TNF therapy. Furthermore, anti-TNF therapy for IBD does not prevent the incidence and progression of fibrosis. A growing body of evidence suggests that IBD pathogenesis is associated with epithelial barrier dysfunction, inappropriate immune responses to luminal microorganisms, and environmental factors as well as host genetics. Recently, a variety of mesenchymal stromal cell populations, including fibroblasts and myofibroblasts, have been characterized in individual tissues under homeostatic and inflammatory conditions. The compositions of fibroblasts and myofibroblasts are altered in the intestinal mucosa of IBD patients, and diverse properties of these cells, such as the production of pro-inflammatory cytokines and extracellular matrix components, are remodeled. Several studies have demonstrated that IBD-specific fibroblasts are involved in anti-TNF therapy refractoriness. Therefore, a better understanding of the interaction among fibroblasts, epithelial cells, immune cells, and microbes associated with the maintenance and perturbation of intestinal homeostasis may facilitate the identification of novel therapeutic targets for IBD. This review presents the key findings obtained to date regarding the pathological and homeostatic mechanisms by which functionally distinct fibroblasts and myofibroblasts regulate epithelial barrier integrity, immunity, and tissue regeneration in health and in gastrointestinal disorders.
B10 cells promote pro-resolving macrophage function through direct cell-cell contact and IL-10 secretion in Raw 264.7 cells.
Memida T, Abdolahinia ED, Cao G … +7 more , Ruiz S, Huang S, Shindo S, Nakamura S, Lin J, Kawai T, Han X
Int Immunol · 2025 Jul · PMID 40056161 · Full text
It is well known that regulatory B cells (Breg), especially IL-10-producing regulatory cells (B10), play an important role in immune regulation during inflammatory and infectious diseases. Although it has been revealed t...
It is well known that regulatory B cells (Breg), especially IL-10-producing regulatory cells (B10), play an important role in immune regulation during inflammatory and infectious diseases. Although it has been revealed that the immune regulatory function of B10 can be exerted through cognate cell-cell contact with T cells, more research is needed to delineate its impact on other key cellular immune components within the immune microenvironment. In this study, we evaluated the effect of B10 on the phenotypic change of macrophages and their pro-resolving functional activities using various co-culture systems. The roles of cell-cell contact and the IL-10 secretion by B10 on macrophage differentiation and function were determined. Splenocyte-derived B10 cells from wild-type or IL-10 knockout (KO) mice were co-cultured with RAW 264.7 cells in the presence or absence of trans-well inserts. Macrophage polarization, programmed cell death 1 (PD-1) expression, production of specialized pro-resolving mediators (SPMs), and phagocytic activity were evaluated. The results showed that direct B10-macrophage co-culture enhanced the macrophage polarization towards a pro-resolving phenotype and their PD-1 expression, which was diminished when the cultured B10 and macrophages were separated by trans-well inserts, or when B cells from IL-10 KO mice were used for the co-culture. In addition, B10 was found to promote the release of specific SPM [resolvin D series 5 (RvD5)] and phagocytic activity by macrophages after co-culture. These effects were compromised in trans-well co-culture or co-cultures with IL-10-deficient B cells. Our results suggest that B10 promotes pro-resolving macrophage differentiation and function through direct cell-cell contact and IL-10 secretion.
The TET-TDG axis in T cells and biological processes.
Suzuki K, Rao A, Onodera A
Int Immunol · 2025 May · PMID 39921704 · Full text
Ten-eleven translocation (TET) proteins are dioxygenases that sequentially oxidize the methyl group of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC). All t...
Ten-eleven translocation (TET) proteins are dioxygenases that sequentially oxidize the methyl group of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC). All three epigenetic modifications are intermediates in DNA demethylation. In the "passive" (replication-dependent) DNA demethylation pathway, sequential oxidation reactions by TETs are essential and modified cytosines (C) are diluted at each cycle of DNA replication. In the "active" (replication-independent) DNA demethylation pathway, both thymine DNA glycosylase (TDG) and TETs play important roles. TDG removes 5fC and 5caC from 5fC:G and 5caC:G base pairs and these modified bases are replaced by unmodified C via base excision repair. Through epigenetic regulation of DNA demethylation, TETs and TDG are involved in cell development, differentiation, and homeostasis. The interplay between TDG and TETs is involved in embryo development, stem cell differentiation, neural development, immune responses, and tumorigenesis. Loss-of-function mutations of TET proteins in immune cells are associated with a variety of abnormalities, including inflammation, cancer, and clonal hematopoiesis, a condition related to aging. Loss of TETs also has a significant impact on the plasticity and differentiation of T cells, which contributes to inflammation and cancer. In this review, we describe recent findings in functions of TETs in T cell plasticity and differentiation and the TET-TDG axis in selected biological processes.
Correlation of interferons and autoimmune aspects in long COVID-19 patients.
Hattori F, Nishiyama J, Hasuo H
Int Immunol · 2025 May · PMID 39921694 · Full text
Long COVID, or post-acute sequelae of COVID-19 (PASC), represents a major global health challenge, with its underlying mechanisms remaining poorly understood despite substantial research and clinical trials. This study i...
Long COVID, or post-acute sequelae of COVID-19 (PASC), represents a major global health challenge, with its underlying mechanisms remaining poorly understood despite substantial research and clinical trials. This study investigates the role of the interferon (IFN) axis in the pathogenesis of PASC, drawing parallels to systemic lupus erythematosus (SLE). The potential pathogenic role of IFNs was detected by meta-analyses of mRNA sequencing data comparing PASC patients to healthy controls. We analyzed serum samples from 39 PASC patients and found significant correlations among multiple IFN sub types, including IFN alpha-2, beta, gamma, lambda-1, and lambda-2/3. The biological activity of IFNs in the serum was positively correlated with levels of both total and type III IFNs. Notably, we detected the widespread presence of anti-double-stranded DNA (anti-dsDNA) and anti-Smith (anti-Sm) antibodies in these patients, with anti-dsDNA levels showing a strong correlation with IFN activity. On the basis of these findings, we propose a hypothetical autoimmune pathogenesis for PASC highlighting the crucial role of IFN signaling.
CD20 and CD19 promote proliferation driven by the IgM-TLR9-L265P MyD88 complex.
Kobayashi Y, Sato R, Shimizu Y … +5 more , Fukui R, Shibata T, Tsukamoto H, Tsubata T, Miyake K
Int Immunol · 2025 May · PMID 39868594 · Full text
The cancer driver mutation L265P MyD88 is found in approximately 30% of cases in the activated B cell-like subgroup of diffuse large B cell-like lymphoma (ABC DLBCL). L265P MyD88 forms a complex with TLR9 and IgM, referr...
The cancer driver mutation L265P MyD88 is found in approximately 30% of cases in the activated B cell-like subgroup of diffuse large B cell-like lymphoma (ABC DLBCL). L265P MyD88 forms a complex with TLR9 and IgM, referred to as the My-T-BCR complex, to drive proliferation. We here show that the B cell surface molecules CD19 and CD20 enhance proliferation mediated by the My-T-BCR complex. Using the interleukin 3 (IL-3)-dependent Ba/F3 line transduced to express the IgM complex (IgM, CD79a, and CD79b) and TLR9, we observed proliferation in the presence of anti-IgM antibody and the TLR9 ligand CpG-B. TLR9 was constitutively associated with IgM and L252P MyD88. CD19 promoted proliferation with anti-IgM and CpG-B specifically in L252P MyD88-expressing Ba/F3 cells, while CD20 enhanced the proliferation in both wild-type- and L252P MyD88-expressing Ba/F3 cells. Additionally, CD20 uniquely enabled IgM-mediated proliferation in L252P MyD88-expressing Ba/F3 cells. Although CpG-B was not required for this proliferation, TLR9 expression remained indispensable. In the ABC DLBCL line TMD8, anti-IgM antibody-mediated growth was impaired by the lack of CD20 and CD19 or of TLR9. Mechanistically, CD19 promoted IgM-dependent AKT phosphorylation, whereas CD20 increased expression of cell surface IgM, thereby enhancing the formation of the IgM-TLR9 complex. These findings suggest that CD19 and CD20 differentially contribute to the proliferation driven by the My-T-BCR complex.
Beneficial effects on T cells by photodynamic therapy with talaporfin enhance cancer immunotherapy.
Ezzaldeen EM, Yaguchi T, Imagawa R … +7 more , Soltan MA, Hirata A, Murakami K, Tsukamoto H, Muto M, Honjo T, Chamoto K
Int Immunol · 2025 May · PMID 39842944 · Full text
Photodynamic therapy (PDT), a local cancer treatment using photosensitizers, has been reported to enhance antitumor immune responses by inducing immunogenic cell death. Although several studies have demonstrated the syne...
Photodynamic therapy (PDT), a local cancer treatment using photosensitizers, has been reported to enhance antitumor immune responses by inducing immunogenic cell death. Although several studies have demonstrated the synergistic antitumor effects of PDT and immune checkpoint blockage (ICB), the detailed underlying mechanisms remain poorly understood. In this study, we investigated the immunological effects of PDT with talaporfin (Tal-PDT), a clinically approved photosensitizer, using bilateral tumor-bearing mouse models. Treatment with Tal-PDT on the tumor on one side of the mouse resulted in tumor growth inhibition on the untreated opposite side. This phenomenon, accompanied by tumor antigen-specific immune reactions, is indicative of an abscopal effect. When combined with anti PD-L1 antibody, synergistic antitumor effects were observed on both the laser-treated and untreated sides. Mechanistically, Tal-PDT enhanced the induction of XCR-1+ dendritic cells in the proximal draining lymph node likely through the induction of ferroptosis in tumor cells. This, in turn, led to the systemic generation of precursor-exhausted CD8+ T cells. Moreover, talaporfin was selectively incorporated into tumor cells rather than into tumor-infiltrating T cells in vivo, leading to targeted tumor killing while preserving T cells. These beneficial effects of Tal-PDT on antitumor immunity collectively enhance ICB cancer immunotherapy. Our study demonstrates the potential of combining Tal-PDT with ICB therapy for clinical applications.
Cancer immunotherapy in progress-an overview of the past 130 years.
Ikeda H
Int Immunol · 2025 Apr · PMID 39792088 · Full text
Since the first approval of an immune checkpoint inhibitor, we have witnessed the clinical success of cancer immunotherapy. Adoptive T-cell therapy with chimeric antigen receptor T (CAR-T) cells has shown remarkable effi...
Since the first approval of an immune checkpoint inhibitor, we have witnessed the clinical success of cancer immunotherapy. Adoptive T-cell therapy with chimeric antigen receptor T (CAR-T) cells has shown remarkable efficacy in hematological malignancies. Concurrently with these successes, the cancer immunoediting concept that refined the cancer immunosurveillance concept underpinned the scientific mechanism and reason for past failures, as well as recent breakthroughs in cancer immunotherapy. Now, we face the next step of issues to be solved in this field, such as tumor heterogeneity, the tumor microenvironment, the metabolism of tumors and the immune system, and personalized approaches for patients, aiming to expand the population benefitted by the therapies.
Intestinal Foxl1+ cell-derived CXCL12 maintains epithelial homeostasis by modulating cellular metabolism.
Yagita-Sakamaki M, Ito T, Sakaguchi T … +12 more , Shimma S, Li B, Okuzaki D, Motooka D, Nakamura S, Hase K, Fukusaki E, Kikuchi A, Nagasawa T, Kumanogoh A, Takeda K, Kayama H
Int Immunol · 2025 Mar · PMID 39774647 · Publisher ↗
Several mesenchymal cell populations are known to regulate intestinal stem cell (ISC) self-renewal and differentiation. However, the influences of signaling mediators derived from mesenchymal cells other than ISC niche f...
Several mesenchymal cell populations are known to regulate intestinal stem cell (ISC) self-renewal and differentiation. However, the influences of signaling mediators derived from mesenchymal cells other than ISC niche factors on epithelial homeostasis remain poorly understood. Here, we show that host and microbial metabolites, such as taurine and gamma-aminobutyric acid (GABA), act on PDGFRαhigh Foxl1high sub-epithelial mesenchymal cells to regulate their transcription. In addition, we found that CXC chemokine ligand 12 (CXCL12) produced from Foxl1high sub-epithelial mesenchymal cells induces epithelial cell cycle arrest through modulation of the mevalonate-cholesterol synthesis pathway, which suppresses tumor progression in ApcMin/+ mice. We identified that Foxl1high sub-epithelial cells highly express CXCL12 among colonic mesenchymal cells. Foxl1-cre; Cxcl12f/f mice showed an increased number of Ki67+ colonic epithelial cells. CXCL12-induced Ca2+ mobilization facilitated phosphorylation of AMPK in intestinal epithelial cells, which inhibits the maturation of sterol regulatory element-binding proteins (SREBPs) that are responsible for mevalonate pathway activation. Furthermore, Cxcl12 deficiency in Foxl1-expressing cells promoted tumor development in the small and large intestines of ApcMin/+ mice. Collectively, these results demonstrate that CXCL12 secreted from Foxl1high mesenchymal cells manipulates intestinal epithelial cell metabolism, which links to the prevention of tumor progression in ApcMin/+ mice.
IL-5-producing Group 2 innate lymphoid cells promote T cell-independent IgA production in cooperation with eosinophils.
Yanagibashi T, Ikutani M, Nagai T … +4 more , Arita M, Watanabe Y, Nagai Y, Takatsu K
Int Immunol · 2025 Apr · PMID 39656643 · Publisher ↗
Intestinal bacteria play a critical role in the regulation of the host immune system and an imbalance in the intestinal bacterial composition induces various host diseases. Therefore, maintaining a balance in the intesti...
Intestinal bacteria play a critical role in the regulation of the host immune system and an imbalance in the intestinal bacterial composition induces various host diseases. Therefore, maintaining a balance in the intestinal bacterial composition is crucial for health. Immunoglobulin A (IgA), produced through T cell-dependent and T cell-independent (TI) pathways, is essential for host defense against pathogen invasion and maintaining the balance of intestinal symbiotic bacteria. Interleukin (IL)-5 is constitutively produced by Group 2 innate lymphoid cells (ILC2s) and plays a critical role in the survival and proliferation of B cells and eosinophils. Here, we show the role of IL-5-producing ILC2s in intestinal TI IgA production at steady state using T cell receptor α deficient mice. In this mouse model, ILC2s increased fecal TI IgA levels in a non-inflammatory state in an IL-5-dependent manner. The administration of recombinant IL-33 (rIL-33) increased the amount of TI IgA production, accompanied by an increase in the number of IL-5-producing ILC2s in the large intestine. In addition, rIL-33 treatment increased IL-5-dependent IgA+ cells in isolated lymphoid follicles, the site of TI IgA production. Furthermore, eosinophils recruited by ILC2s were required for the maximal production of IgA in the TI pathway. Moreover, IL-5 increased the frequency of TI IgA-binding intestinal bacteria and was involved in the maintenance of intestinal bacterial composition. These findings indicate that IL-5-producing ILC2s together with eosinophils contribute to TI IgA production. In addition to their role in TI IgA production, IL-5-producing ILC2s may contribute to the homeostasis of intestinal commensal bacteria.
A complex of NLRP3 with caspase-4 is essential for inflammasome activation by Tannerella forsythia infection.
Hsu CW, Okano T, Niinuma Y … +6 more , Leewananthawet A, Iida T, Onsoi P, Boonyaleka K, Ashida H, Suzuki T
Int Immunol · 2025 Apr · PMID 39673522 · Publisher ↗
Periodontitis, a chronic inflammatory disease of periodontal tissue, is often associated with a group of pathogenic bacteria known as the "red complex", including Tannerella forsythia. Previous papers showed that T. fors...
Periodontitis, a chronic inflammatory disease of periodontal tissue, is often associated with a group of pathogenic bacteria known as the "red complex", including Tannerella forsythia. Previous papers showed that T. forsythia induces many kinds of inflammatory cytokines including interleukin (IL)-1β regulated by inflammasome activation. However, the physiological function of periodontitis and the mechanism to induce inflammasome activation by T. forsythia infection are poorly understood. In this study, we demonstrate that the Nod-like receptor pyrin domain containing 3 (NLRP3) and caspase-4 are essential for inflammasome activation by T. forsythia infection, playing a crucial role in IL-1β maturation in THP-1 cells. We also showed that the knockout of ASC or Gasdermin D suppresses pyroptotic cell death. Moreover, co-immunoprecipitation assays confirmed the formation of a complex involving caspase-4, NLRP3, and ASC following T. forsythia infection. Additionally, reactive oxygen species production was identified as a key factor in caspase-4-mediated NLRP3 inflammasome activation by T. forsythia infection. These results enhance our understanding of inflammasome activation in response to T. forsythia infection and provide new insights into the pathogenic mechanisms of periodontitis.
Analysis of antigen specificity of Treg clonotypes expanded upon SARS-CoV-2 infection.
Takeuchi Y, Ishikawa E, Sato T … +4 more , Shinkai M, Takahashi Y, Lu X, Yamasaki S
Int Immunol · 2025 Apr · PMID 39665863 · Publisher ↗
The pandemic outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has threatened human health worldwide. Among protective immune reactions, T cell responses are diverse among individuals, which is rel...
The pandemic outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has threatened human health worldwide. Among protective immune reactions, T cell responses are diverse among individuals, which is related to the differences in severity. A T cell subset, regulatory T (Treg) cells, is crucial for limiting excessive immune responses. If SARS-CoV-2-specific Tregs are developed during infection, they may counteract antiviral immunity and cause severe symptoms. To address this possibility, we conducted single-cell TCR-RNA-sequencing of peripheral blood mononuclear cells from convalescent Coronavirus disease 2019 (COVID-19) patients. Among 13 donors, one with severe symptoms had substantially more FOXP3-expressing Treg clonotypes activated in the presence of SARS-CoV-2 virion or other major antigen proteins. To define the reactivity of these Treg clonotypes, 15 highly expanded Treg clonotypes were reconstituted into reporter cells and stimulated with 27 distinct peptide pools that cover all SARS-CoV-2 proteins. However, none of these clonotypes react to any SARS-CoV-2 antigens. Instead, the reporter cells expressing one TCR clonotype (23599) were activated in the presence of Epstein-Barr virus-transformed B cells without adding exogenous antigens. Furthermore, 23599 TCR-expressing cells were activated by non-transformed naïve syngeneic B cells in a DQA1*03:03-DQB1*04:01-dependent manner, suggesting that clonotype 23599 may be autoreactive. This Treg clonotype, 23599, was also detected in a public TCR database and significantly expanded in COVID-19 patients compared to healthy donors. These results suggest that SARS-CoV-2 is not the dominant antigen inducing Treg cells during infection.
The immune memory of innate immune systems.
Kato Y, Kumanogoh A
Int Immunol · 2025 Mar · PMID 39588905 · Publisher ↗
Immune memory has long been considered a function specific to adaptive immune systems; however, adaptive immune memory alone has not fully explained the mechanism by which vaccines exert their protective effects against...
Immune memory has long been considered a function specific to adaptive immune systems; however, adaptive immune memory alone has not fully explained the mechanism by which vaccines exert their protective effects against nontarget pathogens. Recently, trained immunity, in which human monocytes vaccinated with bacillus Calmette-Guérin become highly responsive to pathogens other than Mycobacterium tuberculosis, has been reported. However, a phenomenon called endotoxin tolerance is also known, in which monocyte responsiveness is attenuated after the first lipopolysaccharide stimulation. These phenomena represent an altered innate immune response after the initial exposure to the stimulus, indicating that memories are formed in the innate immune system. In this review, we discuss trained immunity and endotoxin tolerance, known as innate immune memory, and innate immune memory formation by mRNA vaccines, which have been newly used in the coronavirus disease 2019 (COVID-19) pandemic and are considered important vaccine modalities in the future.
The role of polyreactive memory B cells in systemic lupus erythematosus.
Fujio K, Ushijima T, Okamura T … +1 more , Ota M
Int Immunol · 2025 Mar · PMID 39514642 · Full text
In systemic lupus erythematosus (SLE), the production of autoantibodies is a crucial characteristic, and B cells play a significant role in its pathogenesis. B cells are the immune cells most associated with the genetic...
In systemic lupus erythematosus (SLE), the production of autoantibodies is a crucial characteristic, and B cells play a significant role in its pathogenesis. B cells are the immune cells most associated with the genetic predispositions of SLE, and recent clinical studies showing that anti-CD19 chimeric antigen receptor (CAR)-T cell therapy induces drug-free remission have underscored the importance of B cells in SLE. Meanwhile, various B-cell subsets exist across different stages of differentiation, from naive B cells to plasma cells, and identifying the important subpopulations within SLE remains a critical future challenge. Years of B-cell repertoire analyses have revealed the importance of polyreactive B-cell receptors (BCRs) and autoantibodies that react to various self-antigens and microbial antigens. Particularly, memory B cells with polyreactive BCRs, which play a crucial role in biological defense during the fetal stage, are characteristically differentiated in SLE. Type I interferon-mediated expression of CXCL13 and IL-21 in CD4+ T cells is associated with the development of polyreactive memory B cells. The expansion of the polyreactive B-cell repertoire, vital for defending against infections such as viruses, may exert an intrinsic function in SLE.
Ro5-4864, a translocator protein ligand, regulates T cell-mediated inflammatory responses in skin.
Sendai Y, Takeda K, Ohta K … +8 more , Nakae S, Koshika K, Kitamura K, Higuchi M, Ichinohe T, Azuma T, Okumura K, Ohno T
Int Immunol · 2025 Mar · PMID 39460731 · Publisher ↗
Translocator protein (TSPO) is a mitochondrial outer membrane protein expressed on a variety of immune cells, including macrophages, dendritic cells, and T cells, in addition to neurons and steroid-producing cells. Previ...
Translocator protein (TSPO) is a mitochondrial outer membrane protein expressed on a variety of immune cells, including macrophages, dendritic cells, and T cells, in addition to neurons and steroid-producing cells. Previous studies of TSPO ligands have suggested that TSPO is involved in multiple cellular functions, including steroidogenesis, immunomodulation, and cell proliferation. Currently, there are limited reports on the effects of TSPO or TSPO ligands on T cell-mediated immune responses. Here, we investigated the involvement of TSPO/TSPO ligand in T cell responses using a 2,4-dinitro-1-fluorobenzene (DNFB)-induced contact hypersensitivity (CH) model. Treatment with Ro5-4864, a TSPO ligand, during DNFB sensitization reduced the number and activation status of CD4+ and CD8+ T cells in draining lymph nodes and alleviated skin inflammation after DNFB challenge. Adoptive transfer of Ro5-4864-treated mouse-derived DNFB-sensitized T cells to naive mice inhibited CH responses after DNFB challenge. Ro5-4864-treated sensitized T cells showed lower proliferative responses when stimulated with DNFB-pulsed antigen-presenting cells compared to control-treated sensitized T cells. Ro5-4864 also suppressed cell proliferation, as well as adenosine triphosphate and lactate production, during T cell activation. Moreover, the inhibitory effects of Ro5-4864 on T cell responses were conserved in TSPO-deficient cells. Our results suggest that Ro5-4864 inhibits CH responses by suppressing energy metabolism, at least via glycolysis, to reduce the T cell primary response in a TSPO-independent manner.
JunB is required for CD8+ T cell responses to acute infections.
Sarkar S, Taira N, Hsieh TH … +8 more , Chien HC, Hirota M, Koizumi SI, Sasaki D, Tamai M, Seto Y, Miyagi M, Ishikawa H
Int Immunol · 2025 Mar · PMID 39425978 · Full text
Basic-leucine zipper transcription factor ATF-like (BATF) and interferon regulatory factor 4 (IRF4) are crucial transcription factors for the generation of cytotoxic effector and memory CD8+ T cells. JunB is required for...
Basic-leucine zipper transcription factor ATF-like (BATF) and interferon regulatory factor 4 (IRF4) are crucial transcription factors for the generation of cytotoxic effector and memory CD8+ T cells. JunB is required for expression of genes controlled by BATF and IRF4 in CD4+ T cell responses, but the role of JunB in CD8+ T cells remains unknown. Here, we demonstrate that JunB is essential for cytotoxic CD8+ T cell responses. JunB expression is transiently induced, depending on the T cell receptor signal strength. JunB deficiency severely impairs the clonal expansion of effector CD8+ T cells in response to acute infection with Listeria monocytogenes. Junb-deficient CD8+ T cells fail to control transcription and chromatin accessibility of a specific set of genes regulated by BATF and IRF4, resulting in impaired cell survival, glycolysis, and cytotoxic CD8+ T cell differentiation. Furthermore, JunB deficiency enhances the expression of co-inhibitory receptors, including programmed cell death 1 (PD-1) and T cell immunoglobulin mucin-3 (TIM3) upon activation of naive CD8+ T cells. These results indicate that JunB, in collaboration with BATF and IRF4, promotes multiple key events in the early stage of cytotoxic CD8+ T cell responses.
Eosinophil and B-cell dynamics in the milky spots from Schistosoma mansoni-infected mice: comparison with spleen and bone marrow, and extramedullary eosinopoiesis.
Vieira BM, Almeida BF, Machado MP
Int Immunol · 2025 Feb · PMID 39423136 · Publisher ↗
The milky spots (MS) are structures found in the omentum of humans and other vertebrates, representing a fraction of the lymphomyeloid tissue associated with the celom. They majorly consist of B lymphocytes, T lymphocyte...
The milky spots (MS) are structures found in the omentum of humans and other vertebrates, representing a fraction of the lymphomyeloid tissue associated with the celom. They majorly consist of B lymphocytes, T lymphocytes, and macrophages. Also found in smaller quantities are mesothelial, stromal, dendritic, and rare mast cells. In an experimental model of Schistosoma mansoni infection, there is significant activation of the omentum and MS, which exhibit numerous eosinophils. Despite being described for many years, the complete profile of cells found in MS and their functions remains largely unexplored. Here, we evaluate the leukocyte populations of the MS in homeostasis and a murine model of S. mansoni infection. The histopathological characterization, phenotypic profile analysis, and characterization of the eosinophilic potential of progenitors and precursors comparing the MS with the spleen and bone marrow showed significant activation of MS in infected mice, with changes in the profile over the analyzed times, showing signs of migration and activation of eosinophils, with local eosinopoiesis and maintenance of the eosinophilic population. In naive mice, B1a and B1b cells make up only a small fraction of B lymphocytes. However, B1b cells expand significantly during infection, peaking at 60 days post-infection (DPI) before stabilizing by 90 DPI. B1a cells also increase initially but decrease over time. The behavior of MS differs from other primary and secondary lymphoid organs, acting as a central lymphoid organ in cavity immunity.
PP2A negatively regulates NK cell T-bet expression and anti-tumor effector function.
Shinzawa Y, Hara D, Shinguryo Y … +3 more , Yokoyama S, Kawada M, Hayakawa Y
Int Immunol · 2024 Dec · PMID 39404747 · Publisher ↗
The transcription factor T-bet is essential for the anti-tumor effector function of natural killer (NK) cells, but the mechanism regulating its expression in NK cells remains unclear. In this study, we aimed to identify...
The transcription factor T-bet is essential for the anti-tumor effector function of natural killer (NK) cells, but the mechanism regulating its expression in NK cells remains unclear. In this study, we aimed to identify an NK cell-intrinsic regulator that controls T-bet expression. Using T-bet-luciferase reporter assay screening, we identified a protein phosphatase inhibitor as a potential activator of T-bet expression. A series of protein phosphatase 2A (PP2A)-specific inhibitors (PP2Ai) or PP2A siRNA induced the expression of T-bet. In PP2Ai-treated mice, the expression of T-bet and its downstream effector molecules, granzyme B and IFN-γ, was also upregulated in NK cells. Mechanistically, PP2Ai increased the phosphorylation of mTOR and ribosomal protein S6 in NK cells, and mTOR inhibitor canceled the effects of PP2Ai in NK cells. Importantly, NK cells isolated from PP2Ai-treated mice showed higher cytotoxicity and IFN-γ production; therefore, they increased the anti-tumor effector function of NK cells. Accordingly, PP2Ai treatment inhibited lung metastasis of B16 melanoma by NK cell- and mTOR-dependent mechanisms. These results suggest that PP2A negatively regulates NK cell T-bet expression and effector function by an mTOR-dependent mechanism.
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