Molecular and functional heterogeneity of IL-10-producing CD4+ T cells

RIPK1 ablation in T cells results in spontaneous enteropathy and TNF-driven villus atrophy

RIPK1 is a crucial regulator of cell survival, inflammation and cell death. Human RIPK1 deficiency leads to early-onset intestinal inflammation and peripheral T cell imbalance, though its role in αβT cell-mediated intestinal homeostasis remains unclear. In this study, we demonstrate that mice with RIPK1 ablation in conventional αβT cells (Ripk1ΔCD4) developed a severe small intestinal pathology characterized by small intestinal elongation, crypt hyperplasia, and duodenum-specific villus atrophy. Using mixed bone marrow chimeras reveals a survival disadvantage of αβT cells compared to γδT cells in the small intestine. Broad-spectrum antibiotic treatment ameliorates crypt hyperplasia and prevents intestinal elongation, though villus atrophy persists. Conversely, crossing Ripk1ΔCD4 with TNF receptor 1 Tnfr1-/- knockout mice rescues villus atrophy but not intestinal elongation. Finally, combined ablation of Ripk1∆CD4 and Casp8∆CD4 fully rescues intestinal pathology, revealing that αβT cell apoptosis in Ripk1∆CD4 drives the enteropathy. These findings demonstrate that RIPK1-mediated survival of αβT cells is essential for proximal small intestinal homeostasis. In Ripk1∆CD4 mice, the imbalanced T cell compartment drives microbiome-mediated intestinal elongation and TNF-driven villus atrophy.

Microbiota-dependent modulation of intestinal anti-inflammatory CD4+ T cell responses

Barrier organs such as the gastrointestinal tract, lungs, and skin are colonized by diverse microbial strains, including bacteria, viruses, and fungi. These microorganisms, collectively known as the commensal microbiota, play critical roles in maintaining health by defending against pathogens, metabolizing nutrients, and providing essential metabolites. In the gut, commensal-derived antigens are frequently sensed by the intestinal immune system. Maintaining tolerance toward these beneficial microbial species is crucial, as failure to do so can lead to chronic inflammatory conditions like inflammatory bowel disease (IBD) and can even affect systemic immune or metabolic health. The immune system carefully regulates responses to commensals through various mechanisms, including the induction of anti-inflammatory CD4⁺ T cell responses. Foxp3⁺ regulatory T cells (Foxp3+ Tregs) and Type 1 regulatory T cells (Tr1) play a major role in promoting tolerance, as both cell types can produce the anti-inflammatory cytokine IL-10. In addition to these regulatory T cells, effector T cell subsets, such as Th17 cells, also adopt anti-inflammatory functions within the intestine in response to the microbiota. This process of anti-inflammatory CD4+ T cell induction is heavily influenced by the microbiota and their metabolites. Microbial metabolites affect intestinal epithelial cells, promoting the secretion of anti-inflammatory mediators that create a tolerogenic environment. They also modulate intestinal dendritic cells (DCs) and macrophages, inducing a tolerogenic state, and can interact directly with T cells to drive anti-inflammatory CD4⁺ T cell functionality. The disrupted balance of these signals may result in chronic inflammation, with broader implications for systemic health. In this review, we highlight the intricate interplays between commensal microorganisms and the immune system in the gut. We discuss how the microbiota influences the differentiation of commensal-specific anti-inflammatory CD4⁺ T cells, such as Foxp3⁺ Tregs, Tr1 cells, and Th17 cells, and explore the mechanisms through which microbial metabolites modulate these processes. We further discuss the innate signals that prime and commit these cells to an anti-inflammatory fate.

FoxP3-positive T regulatory cells and its effector mechanisms in Crohn's disease: an immunohistochemical and image morphometric analysis on endoscopic mucosal biopsies

OBJECTIVE

Crohn's disease (CD) is an immune inflammatory disorder of the gastrointestinal tract arising from a complex interplay of genetic, environmental, microbiome, and immune factors. Regulatory T cells (Tregs), characterized by FoxP3 expression, are crucial for maintaining immune homeostasis through PD-1/PD-L1 interaction, interleukin (IL)-10 release, and granzyme (GrB) production. This study aimed to elucidate the role of FoxP3 positive (+) Tregs in CD.

METHODS

Segmental colonoscopic biopsies from 46 treatment-naive CD cases (34 adults and 12 children) categorized into noninflamed [n = 32; Nancy histologic index (NHI) 0, 1] and inflamed (n = 100; NHI 2-4) mucosae using NHI. CD4, FoxP3, PD-1, IL-10, and GrB immunoexpression were analyzed by eyeballing and image morphometry. Findings were correlated with activity, granulomas, and skip lesions; and compared with site-matched non-inflammatory bowel disease (IBD) controls (n = 30).

RESULTS

FoxP3+ Tregs, IL-10, PD-1, and GrB expressions were significantly higher in NHI 3-4 mucosae than in NHI 0-1 and controls (P < 0.05). No significant differences were observed between adults and children, whereas those with granulomas had increased expression (P = 0.045). The FoxP3 : CD4 ratio positively correlated with IL-10 (Spearman, r = 0.307, P = 0.002), GrB (r = 0.302, P = 0.002), but not with PD-1 (r = 0.98, P = 0.33).

CONCLUSIONS

Our findings point to the possibility of a qualitative defect in FoxP3+ Tregs in CD. The functional arms of Tregs in CD need to be elucidated further in larger prospective cohorts to validate our observations and pave the way for future immunotherapy.

Interleukin 35-producing B cells prolong the survival of GVHD mice by secreting exosomes with membrane-bound IL-35 and upregulating PD-1/LAG-3 checkpoint proteins

Background: Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is an effective treatment for aggressive hematologic malignancies. However, the risk of developing graft-versus-host disease (GVHD) is a significant barrier to allo-HSCT. GVHD is a debilitating condition with high mortality rates and current therapeutic options for GVHD are limited, with corticosteroids being the standard treatment. However, the adverse effects of steroids make prolonged use difficult, necessitating the development of safer therapies. IL-35-producing B-cells (i35-Bregs) have emerged as critical regulators of immunity during autoimmune diseases. In this study, we investigated whether i35-Bregs immunotherapy can suppress and mitigate GVHD. Methods: We administered a single dose of i35-Bregs (1.5×106) to mice undergoing allo-HSCT and monitored disease severity and survival of GVHD mice over 90 days post-transplantation. We discovered that i35-Bregs secrete exosomes containing membrane-bound IL-35 (i35-Exosomes) and investigated whether ex-vivo generated i35-exosomes can be used as stand-alone immunotherapy for GVHD. i35-Breg-induced expression of cytokines or checkpoint proteins (PD-1, LAG-3, CTLA-4) was analyzed by Flow cytometry, ELISA, and RNA-seq analysis. Characterization of membrane-bound IL-35 was by Proximity ligation assay (PLA), immunohistochemistry/Confocal microscopy and Alpha Fold-Multimer modeling. Results: A single dose of 1.5×106 i35-Breg reduced severity of GVHD and prolonged GVHD survival, with more than 70% i35-Breg-treated mice surviving beyond day-90 post-transplantation while observing 100% mortality among untreated mice by day-45. Contrary to the view that IL-35 is secreted cytokine, we show here that i35-Bregs mitigate GVHD via membrane-bound IL-35 and by secreting i35-exosomes. Furthermore, i35-Bregs or ex-vivo generated i35-exosomes induce alloreactive T-cells to upregulate checkpoint proteins associated with T-cell exhaustion and anergy, inhibiting alloreactive responses and propagating infectious-tolerance mechanisms that suppress GVHD. Importantly, i35-Bregs or i35-exosomes suppresses GVHD by increasing bystander lymphocytes coated with immunosuppressive i35-exosomes. Conclusions: This study demonstrates that i35-Bregs and i35-exosomes play a critical role in mitigating GVHD. The combination of i35-Breg and i35-exosome immunotherapy may be an effective strategy for treating GVHD and other inflammatory diseases.

Genetic insights into the relationship between immune cell traits and abnormal uterine bleeding: A Mendelian randomization study

Abnormal uterine bleeding (AUB) is an inflammatory response involving immune cells, but the relationship between immune cell traits and AUB is highly complex and still largely unclear. This study utilized genetic data from a genome-wide association study of European participants. Mendelian randomization (MR) analysis methods, including inverse variance weighted (IVW) as the primary approach, weighted median, MR Egger regression, and Mendelian randomization pleiotropy residual sum and outlier, were employed for forward and reverse analyses. Sensitivity analyses validated the stability and reliability of the results. The IVW method indicated a potential causal relationship between CD45 on granulocyte (odds ratio [OR] = 0.916, 95% CI: 0.880-0.954, P = 1.974 × 10-5) with a decreased risk of menorrhagia. Two immune cell traits with P values < .001 were worthy of attention, CD25 on naive-mature B cell (OR = 0.935, 95% CI: 0.901-0.970, P = 3.882 × 10-4) may be associated with a decreased risk of menorrhagia, while human leukocyte antigen DR on plasmacytoid dendritic cell (OR = 1.089, 95% CI: 1.038-1.143, P = 5.126 × 10-4) may be associated with an increased risk of amenorrhea. No reverse causation was observed. Sensitivity analysis suggested no heterogeneity or horizontal pleiotropy (P > .05). No immune cell traits associated with or potentially related to oligomenorrhea were found. This MR study highlights the complex relationship between immune cell traits and AUB, offering insights into AUB's pathogenesis and potential biomarkers. Further clinical and in vitro validation is needed to assess these findings, with future research exploring immune modulation therapies for early diagnosis and personalized treatment.

Examination of the causal role of immune cells in non-alcoholic fatty liver disease by a bidirectional Mendelian randomization study

Background

Non-alcoholic fatty liver disease (NAFLD) is a globally widespread disease. Recent investigations have highlighted a close association between immunity and NAFLD, but the causality between them has not been thoroughly examined.

Methods

A total of 731 immunological traits and NAFLD cohorts were derived from genome-wide association study summary data, and single nucleotide polymorphisms significantly associated with immune traits were identified as instrumental variables. Moreover, 731 phenotypes include absolute cell counts, median fluorescence intensity (MFI), morphological parameters, and relative cell counts. The bidirectional two-sample Mendelian randomization (MR) was performed primarily using the inverse-variance weighted methods, and sensitivity analysis was carried out simultaneously.

Results

Four immunophenotypes were identified to exert a protective effect against NAFLD, including HLA-DR+ CD4+ %lymphocytes, SSC-A on CD4+, CD24 MFI on IgD-CD38-, and CD8 MFI on CD28-CD8br. Seven immunophenotypes were identified to be hazardous, including CD28+ CD45RA+ CD8dim%CD8dim, CD127 MFI on CD28+ DN (CD4-CD8-), CD20 MFI on IgD+ CD38br, CD20 MFI on transitional, IgD MFI on transitional, CD3 MFI on central memory CD8br, and CD45 MFI on CD33brHLA-DR+ CD14-. However, reverse MR showed NAFLD had no causal effect on immunophenotypes.

Conclusion

The study demonstrated a potential causal link between several immunophenotypes and NAFLD, which contributes to advancing research and treatment of NAFLD based on immune-mediated mechanisms.

Effects of maternal-offspring supplementation of probiotics and synbiotics on the immunity of offspring Bama mini-pigs

Maternal nutrition is one of the main factors regulating the growth and immunity of piglets. This study aimed to investigate the effects of maternal or maternal-offspring supplementation of antibiotics, probiotics, and synbiotics on the immunity of offspring (21, 65, and 125 day-old) in Bama mini-pigs. The results showed that adding antibiotics to maternal diets increased the plasma IFN-γ level of offspring piglets at 21 day-old. Compared with maternal supplementation, maternal-offspring supplementation of antibiotics decreased the IL-10 level in the spleen, probiotics decreased IL-2, IL-10, and TNF-α levels in the ileum, and synbiotics decreased IL-10 and IFN-γ levels in the ileum of offspring piglets. Moreover, maternal-offspring antibiotics supplementation increased the IL-1β level in the ileum, while probiotics supplementation increased the IL-1β level in the spleen of offspring piglets. Maternal antibiotics supplementation increased the TNF-α level in the ileum at 95 day-old compared with maternal probiotics and synbiotics supplementation. Maternal-offspring antibiotics supplementation increased the IL-1β level in the ileum compared with the probiotics supplementation, while synbiotics supplementation increased the IL-6 level in the ileum than the probiotics and antibiotics supplementation at 95 day-old. Moreover, maternal-offspring probiotics supplementation increased the IL-1β level in the spleen of offspring pigs, which was higher than the maternal probiotics supplementation. These findings suggest that the immune function of the offspring piglets varied depending on the specific approach used for probiotics and synbiotics supplementation.

Cellular immunotherapies and immune cell depleting therapies in inflammatory bowel diseases: the next magic bullet?

Despite significant advances in biologic and small molecule treatments and the emergence of combination therapies to treat inflammatory bowel diseases (IBD) a large unmet need remains to control intestinal inflammation. New approaches targeting several pathways simultaneously with a favorable safety profile and agents that trigger anti-inflammatory pathways to drive durable resolution of inflammation are needed. This article discusses novel cellular immunotherapies and immune cell depleting therapies in IBD, including CAR-T cell approaches, Tr1 and T regulatory (Treg) cells and cell depleting antibodies such as rosnilimab. These novel approaches have the potential to overcome current therapeutic limitations in the treatment of IBD.

From promise to practice: CAR T and Treg cell therapies in autoimmunity and other immune-mediated diseases

Autoimmune diseases, characterized by the immune system's attack on the body's own tissues, affect millions of people worldwide. Current treatments, which primarily rely on broad immunosuppression and symptom management, are often associated with significant adverse effects and necessitate lifelong therapy. This review explores the next generation of therapies for immune-mediated diseases, including chimeric antigen receptor (CAR) T cell and regulatory T cell (Treg)-based approaches, which offer the prospect of targeted, durable disease remission. Notably, we highlight the emergence of CD19-targeted CAR T cell therapies, and their ability to drive sustained remission in B cell-mediated autoimmune diseases, suggesting a possible paradigm shift. Further, we discuss the therapeutic potential of Type 1 and FOXP3+ Treg and CAR-Treg cells, which aim to achieve localized immune modulation by targeting their activity to specific tissues or cell types, thereby minimizing the risk of generalized immunosuppression. By examining the latest advances in this rapidly evolving field, we underscore the potential of these innovative cell therapies to address the unmet need for long-term remission and potential tolerance induction in individuals with autoimmune and immune-mediated diseases.

Regulation of inflammation by Interleukin-10 in the intestinal and respiratory mucosa

Intricate immune regulation is required at mucosal surfaces to allow tolerance to microbiota and harmless allergens and to prevent overexuberant inflammatory responses to pathogens. The cytokine Interleukin-10 (IL-10) is a key mediator of mucosal immune regulation. While IL-10 can be produced by virtually all cells of the immune system, many of its in vivo functions depend upon its production by regulatory or effector T cell populations and its signalling to macrophages, dendritic cells and specific T cell subsets. In this review, we discuss our current understanding of the role of IL-10 in regulation of immune responses, with a focus on its context-specific roles in intestinal homeostasis, respiratory infection and asthma. We highlight the importance of appropriate production and function of IL-10 for balancing pathogen clearance, control of microbiota and host tissue damage, and that precise modulation of IL-10 functions in vivo could present therapeutic opportunities.

A novel Slide-seq based image processing software to identify gene expression at the single cell level

Analysis of gene expression at the single-cell level could help predict the effectiveness of therapies in the field of chronic inflammatory diseases such as arthritis. Here, we demonstrate an adopted approach for processing images from the Slide-seq method. Using a puck, which consists of about 50,000 DNA barcode beads, an RNA sequence of a cell is to be read. The pucks are repeatedly brought into contact with liquids and then recorded with a conventional epifluorescence microscope. The image analysis initially consists of stitching the partial images of a sequence recording, registering images from different sequences, and finally reading out the bases. The new method enables the use of an inexpensive epifluorescence microscope instead of a confocal microscope.

Enhanced Effect of β-Lactoglobulin Immunization in Mice with Mild Intestinal Deterioration Caused by Low-Dose Dextran Sulphate Sodium: A New Experimental Approach to Allergy Studies

BACKGROUND/OBJECTIVES

Cow's milk allergy is one of the most common food allergies in children, and its pathomechanism is still under investigation. Recently, an increasing number of studies have linked food allergy to intestinal barrier dysfunction. The present study aimed to investigate changes in the intestinal microenvironment during the development of β-lactoglobulin (β-lg) allergy under conditions of early intestinal dysfunction.

METHODS

BALB/c mice received intraperitoneal β-lg with Freund's adjuvant, followed by oral β-lg while receiving dextran sulphate sodium salt (DSS) in their drinking water (0.2% w/v). The immunized group without DSS and the groups receiving saline, oral β-lg, or DSS served as controls.

RESULTS

The study showed that the immunization effect was greater in mice with mild intestinal barrier dysfunction. Although DSS did not affect the mice's humoral response to β-lg, in combination with β-lg, it significantly altered their cellular response, affecting the induction and distribution of T cells in the inductive and peripheral tissues and the activation of immune mediators. Administration of β-lg to sensitized mice receiving DSS increased disease activity index (DAI) scores and pro-inflammatory cytokine activity, altered the distribution of claudins and zonulin 1 (ZO-1) in the colonic tissue, and negatively affected the balance and activity of the gut microbiota.

CONCLUSIONS

The research model used appears attractive for studying food allergen sensitization, particularly in relation to the initial events leading to mucosal inflammation and the development of food hypersensitivity.

The role of immune-inflammatory markers in children with complicated and uncomplicated malaria in Enugu, Nigeria

BACKGROUND

There is currently insufficient data regarding immune parameters and relationship with severity of malaria infection in Enugu, Nigeria where the economic and social costs of the disease and its management are extremely high. This study was conducted to determine the relationship between malaria severity and some immune-inflammatory markers among malaria-infected children in Enugu, Nigeria.

METHODS

The study adopted a case control design. Eligible children were categorized into three groups - complicated, uncomplicated and healthy children. Pro-inflammatory cytokines -interferon-gamma (IFN-γ) and tumor necrosis factor-alpha (TNF-α); and anti-inflammatory cytokine - interleukin-10 (IL-10) were assayed using enzyme-linked immunosorbent assay (ELISA) technique, while immune cell ratios - neutrophil lymphocyte ratio (NLR) and monocyte lymphocyte ratio (MLR) were calculated from full blood count results.

RESULTS

The overall mean age of the participants was 7.3 ± 3.4 (range: 6 months - 12 years) and the male-female ratio was 1:1. There was no significant difference between the ages of the three groups (P = 0.44). The Mean levels of IFN-γ, TNF-α, and NLR were higher in complicated than uncomplicated malaria (266.9 ± 66.3pg/ml vs. 62.5 ± 6.4pg/ml, p < 0.001; 140.3 ± 30.0pg/ml vs. 42.0 ± 9.0pg/ml, p < 0.001; and 32.9 ± 16.2pg/ml vs. 17.8 ± 6.0pg/ml, p < 0.001, respectively); and higher in uncomplicated malaria than healthy children (62.5 ± 6.4pg/ml vs. 40.6 ± 9.1pg/ml, p < 0.001; 42.0 ± 9.0pg/ml vs. 105.7 ± 32.1, p < 0.001; 17.8 ± 6.0pg/ml vs. 18.7 ± 6.2pg/ml, p < 0.001, respectively). On the other hand, the mean level of IL-10 is higher in uncomplicated than complicated malaria (105.73 ± 32.06pg/ml vs. 40.60 ± 9.11pg/ml, p < 0.001). There was a positive correlation between NLR and IFN-γ (r = 0.815; p = 0.003), as well as NLR and TNF-α (r = 0.745; p = 0.002).

CONCLUSION

Complicated malaria is associated with higher levels of pro-inflammatory cytokines while uncomplicated malaria is associated with higher levels of anti-inflammatory cytokines. NLR correlates positively with pro-inflammatory cytokines, and could be useful in evaluation for the severity of malaria infection.

Repeated immunization with ATRA-containing liposomal adjuvant transdifferentiates Th17 cells to a Tr1-like phenotype

In many autoimmune diseases, autoantigen-specific Th17 cells play a pivotal role in disease pathogenesis. Th17 cells can transdifferentiate into other T cell subsets in inflammatory conditions, however, there have been no attempts to target Th17 cell plasticity using vaccines. We investigated if autoantigen-specific Th17 cells could be specifically targeted using a therapeutic vaccine approach, where antigen was formulated in all-trans retinoic acid (ATRA)-containing liposomes, permitting co-delivery of antigen and ATRA to the same target cell. Whilst ATRA was previously found to broadly reduce Th17 responses, we found that antigen formulated in ATRA-containing cationic liposomes only inhibited Th17 cells in an antigen-specific manner and not when combined with an irrelevant antigen. Furthermore, this approach shifted existing Th17 cells away from IL-17A expression and transcriptomic analysis of sorted Th17 lineage cells from IL-17 fate reporter mice revealed a shift of antigen-specific Th17 cells to exTh17 cells, expressing functional markers associated with T cell regulation and tolerance. In the experimental autoimmune encephalomyelitis (EAE) mouse model of MS, vaccination with myelin-specific (MOG) antigen in ATRA-containing liposomes reduced Th17 responses and alleviated disease. This highlights the potential of therapeutic vaccination for changing the phenotype of existing Th17 cells in the context of immune mediated diseases.

Wenyang-Tianjing-Jieyu Decoction Improves Depression Rats of Kidney Yang Deficiency Pattern by Regulating T Cell Homeostasis and Inflammation Level

PURPOSE

Chronic inflammation is one of the key mechanisms of depression. Wenyang-Tianjin-Jie Decoction (WTJD) is an effective antidepressant found in the course of diagnosis and treatment, but the mechanism of therapeutic effect is not clear. The study aimed to evaluate the efficacy of WTJD in the kidney yang deficiency (KYD) type of depression rats and reveal its mechanisms.

MATERIALS AND METHODS

We selected forty 6-week-old male Sprague-Dawley rats for the study. We established a KYD [Phellodendron amurense Rupr (Huangbai) solution oral gavage and 4°C environments; 8 weeks] type of depression (chronic unpredictable mild stimulus; 6 weeks) rat model first. After successful modeling, we used WTJD or fluoxetine on rats for 3 weeks. Then we evaluated the depression and KYD behavior. Finally, we observed the expression of key inflammatory factors and proteins in peripheral blood and hippocampus, and further investigated the immune balance of Th17/Treg and Th1/Th2 cells and the activity of their main regulatory pathways JAK2/STAT3 and TLR4/TRAF6/NF-κB.

RESULTS

The imbalance of Th17/Treg and Th1/Th2 cells in rats were related to KYD and depressive symptoms. Through this study, we found that WTJD can inhibit the activity of JAK2/STAT3 and TLR4/TRAF6/NF-κB pathways, balance Th17/Treg and Th1/Th2 cell homeostasis, regulate the levels of inflammatory factors in the hippocampus and peripheral blood, and reverse KYD and depression.

CONCLUSION

This study confirmed that WTJD had a reliable effect on depression rats with KYD, and its mechanism was to regulate the immune homeostasis of hippocampal T cells and related inflammatory factors to improve KYD and depression symptoms in rats.

A molecular signature for IL-10-producing Th1 cells in protozoan parasitic diseases

Control of visceral leishmaniasis (VL) depends on proinflammatory Th1 cells that activate infected tissue macrophages to kill resident intracellular parasites. However, proinflammatory cytokines produced by Th1 cells can damage tissues and require tight regulation. Th1 cell IL-10 production is an important cell-autologous mechanism to prevent such damage. However, IL-10-producing Th1 (type 1 regulatory; Tr1) cells can also delay control of parasites and the generation of immunity following drug treatment or vaccination. To identify molecules to target in order to alter the balance between Th1 and Tr1 cells for improved antiparasitic immunity, we compared the molecular and phenotypic profiles of Th1 and Tr1 cells in experimental VL caused by Leishmania donovani infection of C57BL/6J mice. We also identified a shared Tr1 cell protozoan signature by comparing the transcriptional profiles of Tr1 cells from mice with experimental VL and malaria. We identified LAG3 as an important coinhibitory receptor in patients with VL and experimental VL, and we reveal tissue-specific heterogeneity of coinhibitory receptor expression by Tr1 cells. We also discovered a role for the transcription factor Pbx1 in suppressing CD4+ T cell cytokine production. This work provides insights into the development and function of CD4+ T cells during protozoan parasitic infections and identifies key immunoregulatory molecules.

Tr1 Cells Emerge and Suppress Effector Th17 Cells in Glomerulonephritis

T regulatory type 1 (Tr1) cells, which are defined by their regulatory function, lack of Foxp3, and high expression of IL-10, CD49b, and LAG-3, are known to be able to suppress Th1 and Th17 in the intestine. Th1 and Th17 cells are also the main drivers of crescentic glomerulonephritis (GN), the most severe form of renal autoimmune disease. However, whether Tr1 cells emerge in renal inflammation and, moreover, whether they exhibit regulatory function during GN have not been thoroughly investigated yet. To address these questions, we used a mouse model of experimental crescentic GN and double Foxp3mRFP IL-10eGFP reporter mice. We found that Foxp3neg IL-10-producing CD4+ T cells infiltrate the kidneys during GN progression. Using single-cell RNA sequencing, we could show that these cells express the core transcriptional factors characteristic of Tr1 cells. In line with this, Tr1 cells showed a strong suppressive activity ex vivo and were protective in experimental crescentic GN in vivo. Finally, we could also identify Tr1 cells in the kidneys of patients with antineutrophil cytoplasmic autoantibody-associated GN and define their transcriptional profile. Tr1 cells are currently used in several immune-mediated inflammatory diseases, such as T-cell therapy. Thus, our study provides proof of concept for Tr1 cell-based therapies in experimental GN.

STING activation promotes autologous type I interferon-dependent development of type 1 regulatory T cells during malaria

The development of highly effective malaria vaccines and improvement of drug-treatment protocols to boost antiparasitic immunity are critical for malaria elimination. However, the rapid establishment of parasite-specific immune regulatory networks following exposure to malaria parasites hampers these efforts. Here, we identified stimulator of interferon genes (STING) as a critical mediator of type I interferon production by CD4+ T cells during blood-stage Plasmodium falciparum infection. The activation of STING in CD4+ T cells by cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) stimulated IFNB gene transcription, which promoted development of IL-10- and IFN-γ-coproducing CD4+ T (type I regulatory [Tr1]) cells. The critical role for type I IFN signaling for Tr1 cell development was confirmed in vivo using a preclinical malaria model. CD4+ T cell sensitivity to STING phosphorylation was increased in healthy volunteers following P. falciparum infection, particularly in Tr1 cells. These findings identified STING expressed by CD4+ T cells as an important mediator of type I IFN production and Tr1 cell development and activation during malaria.

Determination of Tr1 cell populations correlating with distinct activation states in acute IAV infection

Type I regulatory (Tr1) cells are defined as FOXP3-IL-10-secreting clusters of differentiation (CD4+) T cells that contribute to immune suppression and typically express the markers LAG-3 and CD49b and other co-inhibitory receptors. These cells have not been studied in detail in the context of the resolution of acute infection in the lung. Here, we identify FOXP3- interleukin (IL)-10+ CD4+ T cells transiently accumulating in the lung parenchyma during resolution of the response to sublethal influenza A virus (IAV) infection in mice. These cells were dependent on IL-27Rα, which was required for timely recovery from IAV-induced weight loss. LAG-3 and CD49b were not generally co-expressed by FOXP3- IL-10+ CD4+ T cells in this model and four populations of these cells based on LAG-3 and CD49b co-expression were apparent [LAG-3-CD49b- (double negative), LAG-3+CD49b+ (double positive), LAG-3+CD49b- (LAG-3+), LAG-3-CD49b+ (CD49b+)]. However, each population exhibited suppressive potential consistent with the definition of Tr1 cells. Notably, differences between these populations of Tr1 cells were apparent including differential dependence on IL-10 to mediate suppression and expression of markers indicative of different activation states and terminal differentiation. Sort-transfer experiments indicated that LAG-3+ Tr1 cells exhibited the capacity to convert to double negative and double positive Tr1 cells, indicative of plasticity between these populations. Together, these data determine the features and suppressive potential of Tr1 cells in the resolution of IAV infection and identify four populations delineated by LAG-3 and CD49b, which likely correspond to different Tr1 cell activation states.

Lineage origin and transcriptional control of autoantigen-specific T-regulatory type 1 cells

T Regulatory type-1 (TR1) cells represent an immunosuppressive T cell subset, discovered over 25 years ago, that produces high levels of interleukin-10 (IL-10) but, unlike its FoxP3+ T regulatory (Treg) cell counterpart, does not express FoxP3 or CD25. Experimental evidence generated over the last few years has exposed a promising role for TR1 cells as targets of therapeutic intervention in immune-mediated diseases. The discovery of cell surface markers capable of distinguishing these cells from related T cell types and the application of next generation sequencing techniques to defining their transcriptional make-up have enabled a more accurate description of this T cell population. However, the developmental biology of TR1 cells has long remained elusive, in particular the identity of the cell type(s) giving rise to bona fide TR1 cells in vivo. Here, we review the fundamental phenotypic, transcriptional and functional properties of this T cell subset, and summarize recent lines of evidence shedding light into its ontogeny.

IFNγ and CTLA-4 Drive Hepatic CD4 T-Cell Tolerance and Protection From Autoimmunity in Mice

BACKGROUND & AIMS

The liver has a distinct capacity to induce immune tolerance to hepatic antigens. Although liver tolerance can be advantageous for preventing autoimmune and inflammatory diseases, it also can be detrimental by preventing immune surveillance of infected or malignant cells. Here, we investigated the immune mechanisms that establish hepatic tolerance.

METHODS

Tolerance was investigated in C-reactive protein (CRP)-myelin basic protein (MBP) mice expressing the neuroantigen MBP in hepatocytes, providing profound resistance to MBP-induced neuroinflammation. Tolerance induction was studied after transfer of MBP-specific CD4 T cells into CRP-MBP mice, and tolerance mechanisms were tested using depleting or blocking antibodies.

RESULTS

Although tolerant CRP-MBP mice display increased numbers of forkhead box P3+ regulatory T cells, we here found them not essential for the maintenance of hepatic tolerance. Instead, upon MBP recognition in the liver, MBP-specific T cells became activated to produce interferon (IFN)γ, which, in turn, induced local up-regulation of recruitment molecules, including Chemokine (C-X-C motif) ligand9 and its receptor C-X-C motif chemokine receptor3, facilitating endothelial translocation and redirection of MBP-specific T cells into the hepatic parenchyma. There, the translocated MBP-specific CD4 T cells partly converted into interleukin 10-producing type 1 regulatory T cells, and significantly up-regulated the expression of immune checkpoint molecules, notably cytotoxic T-lymphocyte-associated protein 4 (CTLA-4). Intriguingly, although liver tolerance was not affected by impairment of interleukin 10 signaling, concomitant blockade of IFNγ and CTLA-4 abrogated hepatic tolerance induction to MBP, resulting in neuroinflammatory autoimmune disease in these mice.

CONCLUSIONS

IFNγ-mediated redirection of autoreactive CD4 T cells into the liver and up-regulation of checkpoint molecules, including CTLA-4, were essential for tolerance induction in the liver, hence representing a potential treatment target for boosting or preventing liver tolerance.

Short-term dietary changes can result in mucosal and systemic immune depression

Omnivorous animals, including mice and humans, tend to prefer energy-dense nutrients rich in fat over plant-based diets, especially for short periods of time, but the health consequences of this short-term consumption of energy-dense nutrients are unclear. Here, we show that short-term reiterative switching to 'feast diets', mimicking our social eating behavior, breaches the potential buffering effect of the intestinal microbiota and reorganizes the immunological architecture of mucosa-associated lymphoid tissues. The first dietary switch was sufficient to induce transient mucosal immune depression and suppress systemic immunity, leading to higher susceptibility to Salmonella enterica serovar Typhimurium and Listeria monocytogenes infections. The ability to respond to antigenic challenges with a model antigen was also impaired. These observations could be explained by a reduction of CD4+ T cell metabolic fitness and cytokine production due to impaired mTOR activity in response to reduced microbial provision of fiber metabolites. Reintroducing dietary fiber rewired T cell metabolism and restored mucosal and systemic CD4+ T cell functions and immunity. Finally, dietary intervention with human volunteers confirmed the effect of short-term dietary switches on human CD4+ T cell functionality. Therefore, short-term nutritional changes cause a transient depression of mucosal and systemic immunity, creating a window of opportunity for pathogenic infection.

Immune cell identifier and classifier (ImmunIC) for single cell transcriptomic readouts

Single cell RNA sequencing has a central role in immune profiling, identifying specific immune cells as disease markers and suggesting therapeutic target genes of immune cells. Immune cell-type annotation from single cell transcriptomics is in high demand for dissecting complex immune signatures from multicellular blood and organ samples. However, accurate cell type assignment from single-cell RNA sequencing data alone is complicated by a high level of gene expression heterogeneity. Many computational methods have been developed to respond to this challenge, but immune cell annotation accuracy is not highly desirable. We present ImmunIC, a simple and robust tool for immune cell identification and classification by combining marker genes with a machine learning method. With over two million immune cells and half-million non-immune cells from 66 single cell RNA sequencing studies, ImmunIC shows 98% accuracy in the identification of immune cells. ImmunIC outperforms existing immune cell classifiers, categorizing into ten immune cell types with 92% accuracy. We determine peripheral blood mononuclear cell compositions of severe COVID-19 cases and healthy controls using previously published single cell transcriptomic data, permitting the identification of immune cell-type specific differential pathways. Our publicly available tool can maximize the utility of single cell RNA profiling by functioning as a stand-alone bioinformatic cell sorter, advancing cell-type specific immune profiling for the discovery of disease-specific immune signatures and therapeutic targets.

Inhibitory IL-10-producing CD4+ T cells are T-bet-dependent and facilitate cytomegalovirus persistence via coexpression of arginase-1

Inhibitory CD4+ T cells have been linked with suboptimal immune responses against cancer and pathogen chronicity. However, the mechanisms that underpin the development of these regulatory cells, especially in the context of ongoing antigen exposure, have remained obscure. To address this knowledge gap, we undertook a comprehensive functional, phenotypic, and transcriptomic analysis of interleukin (IL)-10-producing CD4+ T cells induced by chronic infection with murine cytomegalovirus (MCMV). We identified these cells as clonally expanded and highly differentiated TH1-like cells that developed in a T-bet-dependent manner and coexpressed arginase-1 (Arg1), which promotes the catalytic breakdown of L-arginine. Mice lacking Arg1-expressing CD4+ T cells exhibited more robust antiviral immunity and were better able to control MCMV. Conditional deletion of T-bet in the CD4+ lineage suppressed the development of these inhibitory cells and also enhanced immune control of MCMV. Collectively, these data elucidated the ontogeny of IL-10-producing CD4+ T cells and revealed a previously unappreciated mechanism of immune regulation, whereby viral persistence was facilitated by the site-specific delivery of Arg1.

Association of TIM-3 with anterior uveitis and associated systemic immune diseases: a Mendelian randomization analysis

Background

We aimed to investigate the causal association between TIM-3, an immune checkpoint inhibitor, and anterior uveitis (AU), as well as associated systemic immune diseases.

Materials and methods

We performed two-sample Mendelian randomization (MR) analyses to estimate the causal effects of TIM-3 on AU and three associated systemic diseases, namely ankylosing spondylitis (AS), Crohn's disease (CD), and ulcerative colitis (UC). Single-nucleotide polymorphisms (SNPs) associated with AU, AS, CD, and UC were selected as the outcomes: AU GWAS with 2,752 patients with acute AU accompanied with AS (cases) and 3,836 AS patients (controls), AS GWAS with 968 cases and 336,191 controls, CD GWAS with 1,032 cases and 336,127 controls, and UC GWAS with 2,439 cases and 460,494 controls. The TIM-3 dataset was used as the exposure (n = 31,684). Four MR methods, namely, inverse-variance weighting (IVW), MR-Egger regression, weighted median, and weighted mode, were used in this study. Comprehensive sensitivity analyses were conducted to estimate the robustness of identified associations and the potential impact of horizontal pleiotropy.

Results

Our studies show that TIM-3 is significantly associated with CD using the IVW method (OR = 1.001, 95% CI = 1.0002-1.0018, P-value = 0.011). We also found that TIM-3 may be a protective factor for AU although these results lacked significance (OR = 0.889, 95% CI = 0.631-1.252, P-value = 0.5). No association was observed between the genetic predisposition to particular TIM-3 and susceptibility to AS or UC in this study. No potential heterogeneities or directional pleiotropies were observed in our analyses.

Conclusion

According to our study, a small correlation was observed between TIM-3 expression and CD susceptibility. Additional studies in different ethnic backgrounds will be necessary to further explore the potential roles and mechanisms of TIM-3 in CD.

From bench to bedside: targeting lymphocyte activation gene 3 as a therapeutic strategy for autoimmune diseases

BACKGROUND

Immune checkpoints negatively regulate immune response, thereby playing an important role in maintaining immune homeostasis. Substantial studies have confirmed that blockade or deficiency of immune checkpoint pathways contributes to the deterioration of autoimmune diseases. In this context, focusing on immune checkpoints might provide alternative strategies for the treatment of autoimmunity. Lymphocyte activation gene 3 (LAG3), as a member of immune checkpoint, is critical in regulating immune responses as manifested in multiple preclinical studies and clinical trials. Recent success of dual-blockade of LAG3 and programmed death-1 in melanoma also supports the notion that LAG3 is a crucial regulator in immune tolerance.

METHODS

We wrote this review article by searching the PubMed, Web of Science and Google Scholar databases.

CONCLUSION

In this review, we summarize the molecular structure and the action mechanisms of LAG3. Additionally, we highlight its roles in diverse autoimmune diseases and discuss how the manipulation of the LAG3 pathway can serve as a promising therapeutic strategy as well as its specific mechanism with the aim of filling the gaps from bench to bedside.

The multifaceted nature of IL-10: regulation, role in immunological homeostasis and its relevance to cancer, COVID-19 and post-COVID conditions

Interleukin-10 (IL-10) is a pleiotropic cytokine that has a fundamental role in modulating inflammation and in maintaining cell homeostasis. It primarily acts as an anti-inflammatory cytokine, protecting the body from an uncontrolled immune response, mostly through the Jak1/Tyk2 and STAT3 signaling pathway. On the other hand, IL-10 can also have immunostimulating functions under certain conditions. Given the pivotal role of IL-10 in immune modulation, this cytokine could have relevant implications in pathologies characterized by hyperinflammatory state, such as cancer, or infectious diseases as in the case of COVID-19 and Post-COVID-19 syndrome. Recent evidence proposed IL-10 as a predictor of severity and mortality for patients with acute or post-acute SARS-CoV-2 infection. In this context, IL-10 can act as an endogenous danger signal, released by tissues undergoing damage in an attempt to protect the organism from harmful hyperinflammation. Pharmacological strategies aimed to potentiate or restore IL-10 immunomodulatory action may represent novel promising avenues to counteract cytokine storm arising from hyperinflammation and effectively mitigate severe complications. Natural bioactive compounds, derived from terrestrial or marine photosynthetic organisms and able to increase IL-10 expression, could represent a useful prevention strategy to curb inflammation through IL-10 elevation and will be discussed here. However, the multifaceted nature of IL-10 has to be taken into account in the attempts to modulate its levels.

Decreased SPTBN2 expression regulated by the ceRNA network is associated with poor prognosis and immune infiltration in low‑grade glioma

The majority of low-grade gliomas (LGGs) in adults invariably progress to glioblastoma over time. Spectrin β non-erythrocytic 2 (SPTBN2) is detected in numerous tumors and is involved in tumor occurrence and metastasis. However, the specific roles and detailed mechanisms of SPTBN2 in LGG are largely unknown. The present study performed pan-cancer analysis for the expression and prognosis of SPTBN2 in LGG using The Cancer Genome Atlas and The Genotype-Tissue Expression. Western blotting was used to detect the amount of SPTBN2 between glioma tissues and normal brain tissues. Subsequently, based on expression, prognosis, correlation and immune infiltration, non-coding RNAs (ncRNAs) were identified that regulated SPTBN2 expression. Finally, tumor immune infiltrates associated with SPTBN2 and prognosis were performed. Lower expression of SPTBN2 was correlated with an unfavorable outcome in LGG. A significant correlation between the low SPTBN2 mRNA expression and poor clinicopathological features was observed, including wild-type isocitrate dehydrogenase status (P<0.001), 1p/19q non-codeletion (P<0.001) and elders (P=0.019). The western blotting results revealed that, compared with normal brain tissues, the amount of SPTBN2 was significantly lower in LGG tissues (P=0.0266). Higher expression of five microRNAs (miRs/miRNAs), including hsa-miR-15a-5p, hsa-miR-15b-5p, hsa-miR-16-5p, hsa-miR-34c-5p and hsa-miR-424-5p, correlated with poor prognosis by targeting SPTBN2 in LGG. Subsequently, four long ncRNAs (lncRNAs) [ARMCX5-GPRASP2, BASP1-antisense RNA 1 (AS1), EPB41L4A-AS1 and LINC00641] were observed in the regulation of SPTBN2 via five miRNAs. Moreover, the expression of SPTBN2 was significantly correlated with tumor immune infiltration, immune checkpoint expression and biomarkers of immune cells. In conclusion, SPTBN2 was lowly expressed and correlated with an unfavorable prognosis in LGG. A total of six miRNAs and four lncRNAs were identified as being able to modulate SPTBN2 in a lncRNA-miRNA-mRNA network of LGG. Furthermore, the current findings also indicated that SPTBN2 possessed anti-tumor roles by regulating tumor immune infiltration and immune checkpoint expression.

Modulating AHR function offers exciting therapeutic potential in gut immunity and inflammation

Aryl hydrocarbon receptor (AHR) is a ligand-dependent transcription factor. 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a classical exogenous synthetic ligand of AHR that has significant immunotoxic effects. Activation of AHR has beneficial effects on intestinal immune responses, but inactivation or overactivation of AHR can lead to intestinal immune dysregulation and even intestinal diseases. Sustained potent activation of AHR by TCDD results in impairment of the intestinal epithelial barrier. However, currently, AHR research has been more focused on elucidating physiologic AHR function than on dioxin toxicity. The appropriate level of AHR activation plays a role in maintaining gut health and protecting against intestinal inflammation. Therefore, AHR offers a crucial target to modulate intestinal immunity and inflammation. Herein, we summarize our current understanding of the relationship between AHR and intestinal immunity, the ways in which AHR affects intestinal immunity and inflammation, the effects of AHR activity on intestinal immunity and inflammation, and the effect of dietary habits on intestinal health through AHR. Finally, we discuss the therapeutic role of AHR in maintaining gut homeostasis and relieving inflammation.

A T follicular helper cell origin for T regulatory type 1 cells

Chronic antigenic stimulation can trigger the differentiation of antigen-experienced CD4+ T cells into T regulatory type 1 (TR1) cells, a subset of interleukin-10-producing Treg cells that do not express FOXP3. The identities of the progenitor(s) and transcriptional regulators of this T-cell subset remain unclear. Here, we show that the peptide-major histocompatibility complex class II (pMHCII) monospecific immunoregulatory T-cell pools that arise in vivo in different genetic backgrounds in response to pMHCII-coated nanoparticles (pMHCII-NPs) are invariably comprised of oligoclonal subpools of T follicular helper (TFH) and TR1 cells with a nearly identical clonotypic composition but different functional properties and transcription factor expression profiles. Pseudotime analyses of scRNAseq data and multidimensional mass cytometry revealed progressive downregulation and upregulation of TFH and TR1 markers, respectively. Furthermore, pMHCII-NPs trigger cognate TR1 cell formation in TFH cell-transfused immunodeficient hosts, and T-cell-specific deletion of Bcl6 or Irf4 blunts both the TFH expansion and TR1 formation induced by pMHCII-NPs. In contrast, deletion of Prdm1 selectively abrogates the TFH-to-TR1 conversion. Bcl6 and Prdm1 are also necessary for anti-CD3 mAb-induced TR1 formation. Thus, TFH cells can differentiate into TR1 cells in vivo, and BLIMP1 is a gatekeeper of this cellular reprogramming event.

Erratum: Type 1 regulatory T cell-mediated tolerance in health and disease

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Multicytokine-producing CD4+ T cells characterize the livers of patients with NASH

A role of CD4+ T cells during the progression from nonalcoholic fatty liver disease (NAFLD) to nonalcoholic steatohepatitis (NASH) has been suggested, but which polarization state of these cells characterizes this progression and the development of fibrosis remain unclear. In addition, a gut-liver axis has been suggested to play a role in NASH, but the role of CD4+ T cells in this axis has just begun to be investigated. Combining single-cell RNA sequencing and multiple-parameter flow cytometry, we provide the first cell atlas to our knowledge focused on liver-infiltrating CD4+ T cells in patients with NAFLD and NASH, showing that NASH is characterized by a population of multicytokine-producing CD4+ T cells. Among these cells, only those with a Th17 polarization state were enriched in patients with advanced fibrosis. In parallel, we observed that Bacteroides appeared to be enriched in the intestine of NASH patients and to correlate with the frequency of multicytokine-producing CD4+ T cells. In short, we deliver a CD4+ T cell atlas of NAFLD and NASH, providing the rationale to target CD4+ T cells with a Th17 polarization state to block fibrosis development. Finally, our data offer an early indication to test whether multicytokine-producing CD4+ T cells are part of the gut-liver axis characterizing NASH.

IL-10-producing Th1 cells possess a distinct molecular signature in malaria

Control of intracellular parasites responsible for malaria requires host IFN-γ+T-bet+CD4+ T cells (Th1 cells) with IL-10 produced by Th1 cells to mitigate the pathology induced by this inflammatory response. However, these IL-10-producing Th1 (induced type I regulatory [Tr1]) cells can also promote parasite persistence or impair immunity to reinfection or vaccination. Here, we identified molecular and phenotypic signatures that distinguished IL-10-Th1 cells from IL-10+Tr1 cells in Plasmodium falciparum-infected people who participated in controlled human malaria infection studies, as well as C57BL/6 mice with experimental malaria caused by P. berghei ANKA. We also identified a conserved Tr1 cell molecular signature shared between patients with malaria, dengue, and graft-versus-host disease. Genetic manipulation of primary human CD4+ T cells showed that the transcription factor cMAF played an important role in the induction of IL-10, while BLIMP-1 promoted the development of human CD4+ T cells expressing multiple coinhibitory receptors. We also describe heterogeneity of Tr1 cell coinhibitory receptor expression that has implications for targeting these molecules for clinical advantage during infection. Overall, this work provides insights into CD4+ T cell development during malaria that offer opportunities for creation of strategies to modulate CD4+ T cell functions and improve antiparasitic immunity.

Highly purified and functionally stable in vitro expanded allospecific Tr1 cells expressing immunosuppressive graft-homing receptors as new candidates for cell therapy in solid organ transplantation

The development of new strategies based on the use of Tr1 cells has taken relevance to induce long-term tolerance, especially in the context of allogeneic stem cell transplantation. Although Tr1 cells are currently identified by the co-expression of CD49b and LAG-3 and high production of interleukin 10 (IL-10), recent studies have shown the need for a more exhaustive characterization, including co-inhibitory and chemokines receptors expression, to ensure bona fide Tr1 cells to be used as cell therapy in solid organ transplantation. Moreover, the proinflammatory environment induced by the allograft could affect the suppressive function of Treg cells, therefore stability of Tr1 cells needs to be further investigated. Here, we establish a new protocol that allows long-term in vitro expansion of highly purified expanded allospecific Tr1 (^Exp-allo Tr1). Our expanded Tr1 cell population becomes highly enriched in IL-10 producers (> 90%) and maintains high expression of CD49b and LAG-3, as well as the co-inhibitory receptors PD-1, CTLA-4, TIM-3, TIGIT and CD39. Most importantly, high dimensional analysis of ^Exp-allo Tr1 demonstrated a specific expression profile that distinguishes them from activated conventional T cells (T conv), showing overexpression of IL-10, CD39, CTLA-4 and LAG-3. On the other hand, ^Exp-allo Tr1 expressed a chemokine receptor profile relevant for allograft homing and tolerance induction including CCR2, CCR4, CCR5 and CXCR3, but lower levels of CCR7. Interestingly, ^Exp-allo Tr1 efficiently suppressed allospecific but not third-party T cell responses even after being expanded in the presence of proinflammatory cytokines for two extra weeks, supporting their functional stability. In summary, we demonstrate for the first time that highly purified allospecific Tr1 (^Allo Tr1) cells can be efficiently expanded maintaining a stable phenotype and suppressive function with homing potential to the allograft, so they may be considered as promising therapeutic tools for solid organ transplantation.

Transcriptional re-programming of insulin B-chain epitope-specific T-follicular helper cells into anti-diabetogenic T-regulatory type-1 cells

Systemic delivery of nanoparticles (NPs) coated with mono-specific autoimmune disease-relevant peptide-major histocompatibility complex class II (pMHCII) molecules can resolve organ inflammation in various disease models in a disease-specific manner without impairing normal immunity. These compounds invariably trigger the formation and systemic expansion of cognate pMHCII-specific T-regulatory type 1 (TR1) cells. By focusing on type 1 diabetes (T1D)-relevant pMHCII-NP types that display an epitope from the insulin B-chain bound to the same MHCII molecule (IA^g7) on three different registers, we show that pMHCII-NP-induced TR1 cells invariably co-exist with cognate T-Follicular Helper (TFH)-like cells of quasi-identical clonotypic composition and are oligoclonal, yet transcriptionally homogeneous. Furthermore, these three different TR1 specificities have similar diabetes reversal properties in vivo despite being uniquely reactive against the peptide MHCII-binding register displayed on the NPs. Thus, pMHCII-NP treatment using nanomedicines displaying different epitope specificities results in the simultaneous differentiation of multiple antigen-specific TFH-like cell clones into TR1-like cells that inherit the fine antigenic specificity of their precursors while acquiring a defined transcriptional immunoregulatory program.

Single-cell analysis reveals TLR-induced macrophage heterogeneity and quorum sensing dictate population wide anti-inflammatory feedback in response to LPS

The role of macrophages in controlling tissue inflammation is indispensable to ensure a context-appropriate response to pathogens whilst preventing excessive tissue damage. Their initial response is largely characterized by high production of tumor necrosis factor alpha (TNFα) which primes and attracts other immune cells, thereafter, followed by production of interleukin 10 (IL-10) which inhibits cell activation and steers towards resolving of inflammation. This delicate balance is understood at a population level but how it is initiated at a single-cell level remains elusive. Here, we utilize our previously developed droplet approach to probe single-cell macrophage activation in response to toll-like receptor 4 (TLR4) stimulation, and how single-cell heterogeneity and cellular communication affect macrophage-mediated inflammatory homeostasis. We show that only a fraction of macrophages can produce IL-10 in addition to TNFα upon LPS-induced activation, and that these cells are not phenotypically different from IL-10 non-producers nor exhibit a distinct transcriptional pathway. Finally, we demonstrate that the dynamics of TNFα and IL-10 are heavily controlled by macrophage density as evidenced by 3D hydrogel cultures suggesting a potential role for quorum sensing. These exploratory results emphasize the relevance of understanding the complex communication between macrophages and other immune cells and how these amount to population-wide responses.

Randomized Trial of the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of GSK2831781 in Healthy Japanese and White Participants

This study investigated ethnic differences in the safety, tolerability, pharmacokinetics, and pharmacodynamics of GSK2831781, an anti-lymphocyte activation gene 3 (LAG3) monoclonal antibody, in healthy participants, and determined local tolerability and bioavailability following subcutaneous (SC) administration. A double-blind, randomized study of (A) single intravenous (IV) doses of GSK2831781 450 mg or placebo in Japanese and White participants; and (B) single SC doses of GSK2831781 150 or 450 mg, or placebo in White participants, was conducted. Blood samples for analyses were collected before dosing and over 112 days after dosing. GSK2831781 was well tolerated in Japanese and White participants after both IV and SC doses, with the adverse event profile in Japanese being consistent with other populations. There were no injection site adverse events. There was no evidence of differences in systemic exposure among Japanese and White participants. Systemic exposure did not vary with body weight. SC bioavailability was 76.5%, as estimated using population pharmacokinetic modeling. Full and sustained target engagement and evidence of LAG3⁺ cell depletion (≈53%-66%) were observed in both populations and after both administration routes. No evidence of reduced circulating regulatory T cells (CD4⁺ CD25⁺ CD127^low FoxP3⁺ ) was observed. Following IV and SC administration, GSK2831781 depleted circulating LAG3⁺ T cells with no interethnic difference observed. There were no major impacts on circulating regulatory T cells.

Type 1 regulatory T cell-mediated tolerance in health and disease

Type 1 regulatory T (Tr1) cells, in addition to other regulatory cells, contribute to immunological tolerance to prevent autoimmunity and excessive inflammation. Tr1 cells arise in the periphery upon antigen stimulation in the presence of tolerogenic antigen presenting cells and secrete large amounts of the immunosuppressive cytokine IL-10. The protective role of Tr1 cells in autoimmune diseases and inflammatory bowel disease has been well established, and this led to the exploration of this population as a potential cell therapy. On the other hand, the role of Tr1 cells in infectious disease is not well characterized, thus raising concern that these tolerogenic cells may cause general immune suppression which would prevent pathogen clearance. In this review, we summarize current literature surrounding Tr1-mediated tolerance and its role in health and disease settings including autoimmunity, inflammatory bowel disease, and infectious diseases.

Interleukin-6 cytokine: An overview of the immune regulation, immune dysregulation, and therapeutic approach

Several studies have shown that interleukin 6 (IL-6) is a multifunctional cytokine with both pro-inflammatory and anti-inflammatory activity, depending on the immune response context. Macrophages are among several cells that secrete IL-6, which they express upon activation by antigens, subsequently inducing fever and production of acute-phase proteins from the liver. Moreover, IL-6 induces the final maturation of B cells into memory B cells and plasma cells as well as an adaptive role for short-term energy allocation. Activation of IL-6 receptors results in the intracellular activation of the JAK/STAT pathway with resultant production of inflammatory cytokines. Several mechanisms-controlled IL-6 expression, but aberrant production was shown to be crucial in the pathogenesis of many diseases, which include autoimmune and chronic inflammatory diseases. IL-6 in combination with transforming growth factor β (TGF-β) induced differentiation of naïve T cells to Th17 cells, which is the cornerstone in autoimmune diseases. Recently, IL-6 secretion was shown to form the backbone of hypercytokinemia seen in the Coronavirus disease 2019 (COVID-19)-associated hyperinflammation and multiorgan failure. There are two classes of approved IL-6 inhibitors: anti-IL-6 receptor monoclonal antibodies (e.g., tocilizumab) and anti-IL-6 monoclonal antibodies (i.e., siltuximab). These drugs have been evaluated in patients with rheumatoid arthritis, juvenile idiopathic arthritis, cytokine release syndrome, and COVID-19 who have systemic inflammation. JAK/STAT pathway blockers were also successfully used in dampening IL-6 signal transduction. A better understanding of different mechanisms that modulate IL-6 expression will provide the much-needed solution with excellent safety and efficacy profiles for the treatment of autoimmune and inflammatory diseases in which IL-6 derives their pathogenesis.

Regulatory T cells in erythema nodosum leprosum maintain anti-inflammatory function

Background

The numbers of circulating regulatory T cells (Tregs) are increased in lepromatous leprosy (LL) but reduced in erythema nodosum leprosum (ENL), the inflammatory complication of LL. It is unclear whether the suppressive function of Tregs is intact in both these conditions.

Methods

A longitudinal study recruited participants at ALERT Hospital, Ethiopia. Peripheral blood samples were obtained before and after 24 weeks of prednisolone treatment for ENL and multidrug therapy (MDT) for participants with LL. We evaluated the suppressive function of Tregs in the peripheral blood mononuclear cells (PBMCs) of participants with LL and ENL by analysis of TNFα, IFNγ and IL-10 responses to Mycobacterium leprae (M. leprae) stimulation before and after depletion of CD25+ cells.

Results

30 LL participants with ENL and 30 LL participants without ENL were recruited. The depletion of CD25+ cells from PBMCs was associated with enhanced TNFα and IFNγ responses to M. leprae stimulation before and after 24 weeks treatment of LL with MDT and of ENL with prednisolone. The addition of autologous CD25+ cells to CD25+ depleted PBMCs abolished these responses. In both non-reactional LL and ENL groups mitogen (PHA)-induced TNFα and IFNγ responses were not affected by depletion of CD25+ cells either before or after treatment. Depleting CD25+ cells did not affect the IL-10 response to M. leprae before and after 24 weeks of MDT in participants with LL. However, depletion of CD25+ cells was associated with an enhanced IL-10 response on stimulation with M. leprae in untreated participants with ENL and reduced IL-10 responses in treated individuals with ENL. The enhanced IL-10 in untreated ENL and the reduced IL-10 response in prednisolone treated individuals with ENL was abolished by addition of autologous CD25+ cells.

Conclusion

The findings support the hypothesis that the impaired cell-mediated immune response in individuals with LL is M. leprae antigen specific and the unresponsiveness can be reversed by depleting CD25+ cells. Our results suggest that the suppressive function of Tregs in ENL is intact despite ENL being associated with reduced numbers of Tregs. The lack of difference in IL-10 response in control PBMCs and CD25+ depleted PBMCs in individuals with LL and the increased IL-10 response following the depletion of CD25+ cells in individuals with untreated ENL suggest that the mechanism of immune regulation by Tregs in leprosy appears independent of IL-10 or that other cells may be responsible for IL-10 production in leprosy. The present findings highlight mechanisms of T cell regulation in LL and ENL and provide insights into the control of peripheral immune tolerance, identifying Tregs as a potential therapeutic target.

Increased Expression of Multiple Co-Inhibitory Molecules on Malaria-Induced CD8+ T Cells Are Associated With Increased Function Instead of Exhaustion

Activated cytotoxic CD8+ T cells can selectively kill target cells in an antigen-specific manner. However, their prolonged activation often has detrimental effects on tissue homeostasis and function. Indeed, overwhelming cytotoxic activity of CD8+ T cells can drive immunopathology, and therefore, the extent and duration of CD8+ T cell effector function needs to be tightly regulated. One way to regulate CD8+ T cell function is their suppression through engagement of co-inhibitory molecules to their cognate ligands (e.g., LAG-3, PD-1, TIM-3, TIGIT and CTLA-4). During chronic antigen exposure, the expression of co-inhibitory molecules is associated with a loss of T cell function, termed T cell exhaustion and blockade of co-inhibitory pathways often restores T cell function. We addressed the effect of co-inhibitory molecule expression on CD8+ T cell function during acute antigen exposure using experimental malaria. To this end, we infected OT-I mice with a transgenic P. berghei ANKA strain that expresses ovalbumin (PbTG), which enables the characterization of antigen-specific CD8+ T cell responses. We then compared antigen-specific CD8+ T cell populations expressing different levels of the co-inhibitory molecules. High expression of LAG-3 correlated with high expression of PD-1, TIGIT, TIM-3 and CTLA-4. Contrary to what has been described during chronic antigen exposure, antigen-specific CD8+ T cells with the highest expression of LAG-3 appeared to be fully functional during acute malaria. We evaluated this by measuring IFN-γ, Granzyme B and Perforin production and confirmed the results by employing a newly developed T cell cytotoxicity assay. We found that LAG-3high CD8+ T cells are more cytotoxic than LAG-3low or activated but LAG-3neg CD8+ T cells. In conclusion, our data imply that expression of co-inhibitory molecules in acute malaria is not necessarily associated with functional exhaustion but may be associated with an overwhelming T cell activation. Taken together, our findings shed new light on the induction of co-inhibitory molecules during acute T cell activation with ramifications for immunomodulatory therapies targeting these molecules in acute infectious diseases.

CD4+ T-cell-derived IL-10 promotes CNS inflammation in mice by sustaining effector T cell survival

Interleukin (IL)-10 is considered a prototypical anti-inflammatory cytokine, significantly contributing to the maintenance and reestablishment of immune homeostasis. Accordingly, it has been shown in the intestine that IL-10 produced by Tregs can act on effector T cells, thereby limiting inflammation. Herein, we investigate whether this role also applies to IL-10 produced by T cells during central nervous system (CNS) inflammation. During neuroinflammation, both CNS-resident and -infiltrating cells produce IL-10; yet, as IL-10 has a pleotropic function, the exact contribution of the different cellular sources is not fully understood. We find that T-cell-derived IL-10, but not other relevant IL-10 sources, can promote inflammation in experimental autoimmune encephalomyelitis. Furthermore, in the CNS, T-cell-derived IL-10 acts on effector T cells, promoting their survival and thereby enhancing inflammation and CNS autoimmunity. Our data indicate a pro-inflammatory role of T-cell-derived IL-10 in the CNS.

B Cells Are Not Involved in the Regulation of Adenoviral TGF-β1- or Bleomycin-Induced Lung Fibrosis in Mice

Idiopathic pulmonary fibrosis (IPF) is an irreversible, age-related diffuse parenchymal lung disease of poorly defined etiology. Many patients with IPF demonstrate distinctive lymphocytic interstitial infiltrations within remodeled lung tissue with uncertain pathogenetic relevance. Histopathological examination of explant lung tissue of patients with IPF revealed accentuated lymphoplasmacellular accumulations in close vicinity to, or even infiltrating, remodeled lung tissue. Similarly, we found significant accumulations of B cells interfused with T cells within remodeled lung tissue in two murine models of adenoviral TGF-β1 or bleomycin (BLM)-induced lung fibrosis. Such B cell accumulations coincided with significantly increased lung collagen deposition, lung histopathology, and worsened lung function in wild-type (WT) mice. Surprisingly, B cell-deficient µMT knockout mice exhibited similar lung tissue remodeling and worsened lung function upon either AdTGF-β1 or BLM as for WT mice. Comparative transcriptomic profiling of sorted B cells collected from lungs of AdTGF-β1- and BLM-exposed WT mice identified a large set of commonly regulated genes, but with significant enrichment observed for Gene Ontology terms apparently not related to lung fibrogenesis. Collectively, although we observed B cell accumulations in lungs of IPF patients as well as two experimental models of lung fibrosis, comparative profiling of characteristic features of lung fibrosis between WT and B cell-deficient mice did not support a major involvement of B cells in lung fibrogenesis in mice.

Old and New Biomarkers for Infection, Inflammation, and Autoimmunity in Treatment-Resistant Affective and Schizophrenic Spectrum Disorders

Affective (AF) and Schizophrenic (SZ) Spectrum disorders manifest with risk factors, involving inflammatory processes linked to infections and autoimmunity. This study searched for novel biomarkers in cerebrospinal fluid (CSF) and peripheral blood. A total of 29 AF and 39 SZ patients with treatment-resistant disease were included. In CSF, the chemokine IL-8 was significantly elevated in AF and SZ patients. IL-8 promotes chemotaxis by neutrophils and may originate from different tissues. S100B, a glia-derived brain damage marker, was higher in CSF from AF than SZ patients. Among the plasma-derived biomarkers, ferritin was elevated in AF and SZ. Soluble CD25, indicating Treg dysfunction, was higher in SZ than in AF patients. Interferon-γ, implying virus-specific immune activation, was positive in selective AF patients, only. Both groups showed elevated expression of immunosuppressive CD33 on monocytes, but higher amounts of CD123+ plasmacytoid dendritic cells were restricted to SZ. In conclusion, chemotactic IL-8 indicates neuronal stress and inflammation in the CSF of both groups. Novel plasma-derived biomarkers such as sCD25 and monocytic CD33 distinguish SZ from AF with an autoimmune phenotype.

TRPM2 Is Not Required for T-Cell Activation and Differentiation

Antigen recognition by the T-cell receptor induces a cytosolic Ca²⁺ signal that is crucial for T-cell function. The Ca²⁺ channel TRPM2 (transient receptor potential cation channel subfamily M member 2) has been shown to facilitate influx of extracellular Ca²⁺ through the plasma membrane of T cells. Therefore, it was suggested that TRPM2 is involved in T-cell activation and differentiation. However, these results are largely derived from in vitro studies using T-cell lines and non-physiologic means of TRPM2 activation. Thus, the relevance of TRPM2-mediated Ca²⁺ signaling in T cells remains unclear. Here, we use TRPM2-deficient mice to investigate the function of TRPM2 in T-cell activation and differentiation. In response to TCR stimulation in vitro, Trpm2^-/- and WT CD4⁺ and CD8⁺ T cells similarly upregulated the early activation markers NUR77, IRF4, and CD69. We also observed regular proliferation of Trpm2^-/- CD8⁺ T cells and unimpaired differentiation of CD4⁺ T cells into Th1, Th17, and Treg cells under specific polarizing conditions. In vivo, Trpm2^-/- and WT CD8⁺ T cells showed equal specific responses to Listeria monocytogenes after infection of WT and Trpm2^-/- mice and after transfer of WT and Trpm2^-/- CD8⁺ T cells into infected recipients. CD4⁺ T-cell responses were investigated in the model of anti-CD3 mAb-induced intestinal inflammation, which allows analysis of Th1, Th17, Treg, and Tr1-cell differentiation. Here again, we detected similar responses of WT and Trpm2^-/- CD4⁺ T cells. In conclusion, our results argue against a major function of TRPM2 in T-cell activation and differentiation.

FoxP3- Tr1 Cell in Generalized Myasthenia Gravis and Its Relationship With the Anti-AChR Antibody and Immunomodulatory Cytokines

Introduction: The changes in the number and function of regulatory T cells (Tregs) are thought to play important roles in the pathogenesis of generalized myasthenia gravis (gMG). Previous studies have suggested the decrease of FoxP3⁺ Treg cells in the MG development. However, there is no study on the pathophysiological mechanism of FoxP3⁻Treg, especially Tr1 cells, in gMG patients. Therefore, this study was conducted to reveal the effect of Tr1 cells to the pathophysiology of gMG.

Methods: Thirteen patients with gMG and twelve healthy volunteers were enrolled in this study. The titer of anti-AChR Ab was measured by ELISA. The separated PBMCs were labeled for CD4, CD25, CD49b, LAG3 and FoxP3. The CD4⁺ T cell count, FoxP3⁺ Treg to CD4⁺ T cell ratio and Tr1 cell to CD4⁺ T cell ratio were measured by flow cytometry. Based on the FoxP3⁺ Treg and Tr1 cell to CD4⁺ T cell ratios, the patients' Tr1 cell to FoxP3⁺ Treg ratios were calculated. The IL-6, IL-7, IL-10, TGF-β and IFN-γ concentration in the serum of MG patients and normal controls (NCs) were measured via ELISA.

Results: We found a significantly positive correlation between the Tr1 cell/CD4⁺ T cell ratio and the anti-AChR Ab (r = 0.6889 ± 0.4414, p = 0.0401). Although there were no significant differences in the relationship between FoxP3⁺ Treg cells and anti-AChR Ab, a positive correlation between the Tr1 cell/FoxP3⁺ Treg cell ratio and the anti-AChR Ab (r = 0.7110 ± 0.4227, p = 0.0318) was observed. In addition, the Tr1 cell/CD4⁺ T cell ratio but not the proportion of FoxP3⁺ Tregs was positively correlated with IL-10 (p = 0.048). These results suggested that in the process of the immunomodulatory effect of Tr1 cells in patients with gMG, IL-10 and other cytokines may be involved, but the specific mechanism needs further study.

Conclusion: This is the first study of the immunoregulatory mechanism of Tr1 cells in gMG. We conducted this study to elucidate the significance of Tr1 cells in the pathogenesis of MG. We believe that in patients with gMG, Tr1 cells may play an immunomodulatory role in counteracting AChR-related autoimmune responses. In this process, IL-10 and other immunomodulatory cytokines may be involved.

A Notch/STAT3-driven Blimp-1/c-Maf-dependent molecular switch induces IL-10 expression in human CD4+ T cells and is defective in Crohn´s disease patients

Immunosuppressive Interleukin (IL)-10 production by pro-inflammatory CD4⁺ T cells is a central self-regulatory function to limit aberrant inflammation. Still, the molecular mediators controlling IL-10 expression in human CD4⁺ T cells are largely undefined. Here, we identify a Notch/STAT3 signaling-module as a universal molecular switch to induce IL-10 expression across human naïve and major effector CD4⁺ T cell subsets. IL-10 induction was transient, jointly controlled by the transcription factors Blimp-1/c-Maf and accompanied by upregulation of several co-inhibitory receptors, including LAG-3, CD49b, PD-1, TIM-3 and TIGIT. Consistent with a protective role of IL-10 in inflammatory bowel diseases (IBD), effector CD4⁺ T cells from Crohn's disease patients were defective in Notch/STAT3-induced IL-10 production and skewed towards an inflammatory Th1/17 cell phenotype. Collectively, our data identify a Notch/STAT3-Blimp-1/c-Maf axis as a common anti-inflammatory pathway in human CD4⁺ T cells, which is defective in IBD and thus may represent an attractive therapeutic target.