Interleukin-22: immunobiology and pathology

Cytokine Receptors-Regulators of Antimycobacterial Immune Response

Cytokine receptors are critical regulators of the antimycobacterial immune response, playing a key role in initiating and coordinating the recruitment and activation of immune cells during infection. They recognize and bind specific cytokines and are involved in inducing intracellular signal transduction pathways that regulate a diverse range of biological functions, including proliferation, differentiation, metabolism and cell growth. Due to mutations in cytokine receptor genes, defective signaling may contribute to increased susceptibility to mycobacteria, allowing the pathogens to avoid killing and immune surveillance. This paper provides an overview of cytokine receptors important for the innate and adaptive immune responses against mycobacteria and discusses the implications of receptor gene defects for the course of mycobacterial infection.

Crosstalk between Oxidative Stress and Inflammatory Liver Injury in the Pathogenesis of Alcoholic Liver Disease

Alcoholic liver disease (ALD) is characterized by the injury, inflammation, and scarring in the liver owing to excessive alcohol consumption. Currently, ALD is a leading cause for liver transplantation. Therefore, extensive studies (in vitro, in experimental ALD models and in humans) are needed to elucidate pathological features and pathogenic mechanisms underlying ALD. Notably, oxidative changes in the liver have been recognized as a signature trait of ALD. Progression of ALD is linked to the generation of highly reactive free radicals by reactions involving ethanol and its metabolites. Furthermore, hepatic oxidative stress promotes tissue injury and, in turn, stimulates inflammatory responses in the liver, forming a pathological loop that promotes the progression of ALD. Accordingly, accumulating further knowledge on the relationship between oxidative stress and inflammation may help establish a viable therapeutic approach for treating ALD.

Challenges and opportunities targeting mechanisms of epithelial injury and recovery in acute intestinal graft-versus-host disease

Despite advances in immunosuppressive prophylaxis and overall supportive care, gastrointestinal (GI) graft-versus-host disease (GVHD) remains a major, lethal side effect after allogeneic hematopoietic stem cell transplantation (allo-HSCT). It has become increasingly clear that the intestinal epithelium, in addition to being a target of transplant-related toxicity and GVHD, plays an important role in the onset of GVHD. Over the last two decades, increased understanding of the epithelial constituents and their microenvironment has led to the development of novel prophylactic and therapeutic interventions, with the potential to protect the intestinal epithelium from GVHD-associated damage and promote its recovery following insult. In this review, we will discuss intestinal epithelial injury and the role of the intestinal epithelium in GVHD pathogenesis. In addition, we will highlight possible approaches to protect the GI tract from damage posttransplant and to stimulate epithelial regeneration, in order to promote intestinal recovery. Combined treatment modalities integrating immunomodulation, epithelial protection, and induction of regeneration may hold the key to unlocking mucosal recovery and optimizing therapy for acute intestinal GVHD.

AhR/IL-22 pathway as new target for the treatment of post-infectious irritable bowel syndrome symptoms

Alterations in brain/gut/microbiota axis are linked to Irritable Bowel Syndrome (IBS) physiopathology. Upon gastrointestinal infection, chronic abdominal pain and anxio-depressive comorbidities may persist despite pathogen clearance leading to Post-Infectious IBS (PI-IBS). This study assesses the influence of tryptophan metabolism, and particularly the microbiota-induced AhR expression, on intestinal homeostasis disturbance following gastroenteritis resolution, and evaluates the efficacy of IL-22 cytokine vectorization on PI-IBS symptoms. The Citrobacter rodentium infection model in C57BL6/J mice was used to mimic Enterobacteria gastroenteritis. Intestinal homeostasis was evaluated as low-grade inflammation, permeability, mucosa-associated microbiota composition, and colonic sensitivity. Cognitive performances and emotional state of animals were assessed using several tests. Tryptophan metabolism was analyzed by targeted metabolomics. AhR activity was evaluated using a luciferase reporter assay method. One Lactococcus lactis strain carrying an eukaryotic expression plasmid for murine IL-22 (L. lactisIL-22) was used to induce IL-22 production in mouse colonic mucosa. C. rodentium-infected mice exhibited persistent colonic hypersensitivity and cognitive impairments and anxiety-like behaviors after pathogen clearance. These post-infectious disorders were associated with low-grade inflammation, increased intestinal permeability, decrease of Lactobacillaceae abundance associated with the colonic layer, and increase of short-chain fatty acids (SCFAs). During post-infection period, the indole pathway and AhR activity were decreased due to a reduction of tryptophol production. Treatment with L. lactisIL-22 restored gut permeability and normalized colonic sensitivity, restored cognitive performances and decreased anxiety-like behaviors. Data from the video-tracking system suggested an upgrade of welfare for mice receiving the L.lactisIL-22 strain. Our findings revealed that AhR/IL-22 signaling pathway is altered in a preclinical PI-IBS model. IL-22 delivering alleviate PI-IBS symptoms as colonic hypersensitivity, cognitive impairments, and anxiety-like behaviors by acting on intestinal mucosa integrity. Thus, therapeutic strategies targeting this pathway could be developed to treat IBS patients suffering from chronic abdominal pain and associated well-being disorders.

Loss of aryl hydrocarbon receptor suppresses the response of colonic epithelial cells to IL22 signaling by upregulating SOCS3

IL22 signaling plays an important role in maintaining gastrointestinal epithelial barrier function, cell proliferation, and protection of intestinal stem cells from genotoxicants. Emerging studies indicate that the aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor, promotes production of IL22 in gut immune cells. However, it remains to be determined if AhR signaling can also affect the responsiveness of colonic epithelial cells to IL22. Here, we show that IL22 treatment induces the phosphorylation of STAT3, inhibits colonic organoid growth, and promotes colonic cell proliferation in vivo. Notably, intestinal cell-specific AhR knockout (KO) reduces responsiveness to IL22 and compromises DNA damage response after exposure to carcinogen, in part due to the enhancement of suppressor of cytokine signaling 3 (SOCS3) expression. Deletion of SOCS3 increases levels of pSTAT3 in AhR KO organoids, and phenocopies the effects of IL22 treatment on wild-type (WT) organoid growth. In addition, pSTAT3 levels are inversely associated with increased azoxymethane/dextran sulfate sodium (AOM/DSS)-induced colon tumorigenesis in AhR KO mice. These findings indicate that AhR function is required for optimal IL22 signaling in colonic epithelial cells and provide rationale for targeting AhR as a means of reducing colon cancer risk.NEW & NOTEWORTHY AhR is a key transcription factor controlling expression of IL22 in gut immune cells. In this study, we show for the first time that AhR signaling also regulates IL22 response in colonic epithelial cells by modulating SOCS3 expression.

Amelioration of DSS-Induced Acute Colitis in Mice by Recombinant Monomeric Human Interleukin-22

IL-22, a pleiotropic cytokine, is known to have a profound effect on the regeneration of damaged intestinal barriers. The tissue-protective properties of IL-22 are expected to be potentially exploited in the attenuation and treatment of colitis. However, because of the disease-promoting role of IL-22 in chronic inflammation, a comprehensive evaluation is required to translate IL-22 into the clinical domain. Here, we present the effective production of soluble human IL-22 in bacteria to prove whether recombinant IL-22 has the ability to ameliorate colitis and inflammation. IL-22 was expressed in the form of a biologically active monomer and non-functional oligomers. Monomeric IL-22 (mIL-22) was highly purified through a series of 3 separate chromatographic methods and an enzymatic reaction. We reveal that the resulting mIL-22 is correctly folded and is able to phosphorylate STAT3 in HT-29 cells. Subsequently, we demonstrate that mIL-22 enables the attenuation of dextran sodium sulfate-induced acute colitis in mice, as well as the suppression of pro-inflammatory cytokine production. Collectively, our results suggest that the recombinant mIL-22 is suitable to study the biological roles of endogenous IL-22 in immune responses and can be developed as a biological agent associated with inflammatory disorders.

Novel drug discovery strategies for the treatment of decompensated cirrhosis

INTRODUCTION

Disease progression in cirrhosis leads to decompensation and acute-on-chronic liver failure (ACLF), which is characterized by organ failure and high mortality. Portal hypertension and cardiovascular dysfunction trigger the development of cirrhosis-related complications whilst tissue injury and cellular metabolic dysfunction lead to organ failure. System inflammation is the overarching mechanism mediating both the transition from compensation to decompensation as well as progression to ACLF. Treatment of precipitating events and intensive organ support is the only established therapeutic strategies. Liver transplantationrepresents the only curative therapy but contraindications and organ scarcity limit its availability to only a minority of patients with end-stage liver disease. Therefore, the discovery and development of novel interventions modifying the disease course and improving patients' outcome are of utmost importance.

AREAS COVERED

This review highlights and discusses therapeutic novelties in the field of end-stage liver disease.

EXPERT OPINION

Despite decades of research, there are still no established therapies to improve the devastating prognosis of patients with end-stage liver disease. The clinical heterogeneity and complex pathogenesis will put high demands on drug discovery. Combinatorial therapies tailored to the patients' individual pattern of pathomechanisms may be the most efficient way to modify disease course.

Cross-talk of inflammatory mediators and airway epithelium reveals the cystic fibrosis transmembrane conductance regulator as a major target

Airway inflammation, mucus hyperproduction and epithelial remodelling are hallmarks of many chronic airway diseases, including asthma, COPD and cystic fibrosis. While several cytokines are dysregulated in these diseases, most studies focus on the response of airways to interleukin (IL)-4 and IL-13, which have been shown to induce mucus hyperproduction and shift the airway epithelium towards a hypersecretory phenotype. We hypothesised that other cytokines might induce the expression of chloride (Cl^-) channels/transporters, and regulate epithelial differentiation and mucus production. To this end, fully differentiated human airway basal cells (BCi-NS1.1) were treated with cytokines identified as dysregulated in those diseases, namely IL-8, IL-1β, IL-4, IL-17A, IL-10 and IL-22, and tumour necrosis factor-α. Our results show that the cystic fibrosis transmembrane conductance regulator (CFTR) is the main Cl^- channel modulated by inflammation, in contrast to transmembrane protein 16A (TMEM16A), whose levels only changed with IL-4. Furthermore, we identified novel roles for IL-10 and IL-22 by influencing epithelial differentiation towards ciliated cells and away from pulmonary ionocytes. In contrast, IL-1β and IL-4 reduced the number of ciliated cells while increasing club cells. Interestingly, while IL-1β, IL-4 and IL-10 upregulated CFTR expression, IL-4 was the only cytokine that increased both its function and the number of CFTR-expressing club cells, suggesting that this cell type may be the main contributor for CFTR function. Additionally, all cytokines assessed increased mucus production through a differential upregulation of MUC5AC and MUC5B transcript levels. This study reveals a novel insight into differentiation resulting from the cross-talk of inflammatory mediators and airway epithelial cells, which is particularly relevant for chronic airway diseases.

Therapeutic Opportunities of IL-22 in Non-Alcoholic Fatty Liver Disease: From Molecular Mechanisms to Clinical Applications

Nonalcoholic fatty liver disease (NAFLD) represents one of the most common liver disorders and can progress into a series of liver diseases, including nonalcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and even liver cancer. Interleukin-22 (IL-22), a member of the IL-10 family of cytokines, is predominantly produced by lymphocytes but acts exclusively on epithelial cells. IL-22 was proven to favor tissue protection and regeneration in multiple diseases. Emerging evidence suggests that IL-22 plays important protective functions against NAFLD by improving insulin sensitivity, modulating lipid metabolism, relieving oxidative and endoplasmic reticulum (ER) stress, and inhibiting apoptosis. By directly interacting with the heterodimeric IL-10R2 and IL-22R1 receptor complex on hepatocytes, IL-22 activates the Janus kinase 1 (JAK1)/ signal transducer and activator of transcription 3 (STAT3), c-Jun N-terminal kinase (JNK) and extracellular-signal regulated kinase (ERK) pathways to regulate the subsequent expression of genes involved in inflammation, metabolism, tissue repair, and regeneration, thus alleviating hepatitis and steatosis. However, due to the wide biodistribution of the IL-22 receptor and its proinflammatory effects, modifications such as targeted delivery of IL-22 expression and recombinant IL-22 fusion proteins to improve its efficacy while reducing systemic side effects should be taken for further clinical application. In this review, we summarized recent progress in understanding the physiological and pathological importance of the IL-22-IL-22R axis in NAFLD and the mechanisms of IL-22 in the protection of NAFLD and discussed the potential strategies to maneuver this specific cytokine for therapeutic applications for NAFLD.

Single-cell analysis of human non-small cell lung cancer lesions refines tumor classification and patient stratification

Immunotherapy is a mainstay of non-small cell lung cancer (NSCLC) management. While tumor mutational burden (TMB) correlates with response to immunotherapy, little is known about the relationship between the baseline immune response and tumor genotype. Using single-cell RNA sequencing, we profiled 361,929 cells from 35 early-stage NSCLC lesions. We identified a cellular module consisting of PDCD1⁺CXCL13⁺ activated T cells, IgG⁺ plasma cells, and SPP1⁺ macrophages, referred to as the lung cancer activation module (LCAM^hi). We confirmed LCAM^hi enrichment in multiple NSCLC cohorts, and paired CITE-seq established an antibody panel to identify LCAM^hi lesions. LCAM presence was found to be independent of overall immune cell content and correlated with TMB, cancer testis antigens, and TP53 mutations. High baseline LCAM scores correlated with enhanced NSCLC response to immunotherapy even in patients with above median TMB, suggesting that immune cell composition, while correlated with TMB, may be a nonredundant biomarker of response to immunotherapy.

Intestinal organoids in coculture: redefining the boundaries of gut mucosa ex vivo modeling

All-time preservation of an intact mucosal barrier is crucial to ensuring intestinal homeostasis and, hence, the organism's overall health maintenance. This complex process relies on an equilibrated signaling system between the intestinal epithelium and numerous cell populations inhabiting the gut mucosa. Any perturbations of this delicate cross talk, particularly regarding the immune cell compartment and microbiota, may sustainably debilitate the intestinal barrier function. As a final joint event, a critical rise in epithelial permeability facilitates the exposure of submucosal immunity to microbial antigens, resulting in uncontrolled inflammation, collateral tissue destruction, and dysbiosis. Organoid-derived intestinal coculture models have established themselves as convenient tools to reenact such pathophysiological events, explore interactions between selected cell populations, and assess their roles with a central focus on intestinal barrier recovery and stabilization.

A Potential Probiotic for Diarrhea: Clostridium tyrobutyricum Protects Against LPS-Induced Epithelial Dysfunction via IL-22 Produced By Th17 Cells in the Ileum

Probiotics are clinically used for diarrhea and inflammatory bowel diseases in both humans and animals. Previous studies have shown that Clostridium tyrobutyricum (Ct) protects against intestinal dysfunction, while its regulatory function in the gut needs further investigation and the related mechanisms are still not fully elucidated. This study aims to further verify the protective function of Ct and reveal its underlying mechanisms in alleviating diarrhea and intestinal inflammation. Ct inhibited LPS-induced diarrhea and intestinal inflammation in the ileum. IL-22 was identified and the protective role of Ct in the ileum presented an IL-22-dependent manner according to the transcriptomic analysis and in vivo interference mice experiments. The flow cytometric analysis of immune cells in the ileum showed that Ct enhanced the proportions of Th17 cells in response to LPS. The results of in situ hybridization further verified that Ct triggered Th17 cells to produce IL-22, which combined with IL-22RA1 expressed in the epithelial cells. Moreover, Ct was unable to enhance the levels of short-chain fatty acids (SCFAs) in the ileum, suggesting that the protective role of Ct in the ileum was independent of SCFAs. This study uncovered the role of Ct in alleviating diarrhea and inflammation with the mechanism of stimulating Th17 cells in the lamina propria to produce IL-22, highlighting its potential application as a probiotic for diarrhea and inflammation in the ileum.

Inhibition of Prostaglandin F2α Receptors Exaggerates HCl-Induced Lung Inflammation in Mice

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are severe respiratory disorders that are caused by aspiration, sepsis, trauma, and pneumonia. A clinical feature of ALI/ARDS is the acute onset of severe hypoxemia, and the mortality rate, which is estimated at 38-50%, remains high. Although prostaglandins (PGs) are detected in the bronchoalveolar lavage fluid of patients with ALI/ARDS, the role of PGF_2α in ALI remains unclear. We aimed to clarify the role of PGF_2α/PGF_2α receptor (FP) signaling in acid-induced ALI using an FP receptor antagonist, AL8810. Intratracheal injection of hydrochloric acid (HCl) increased neutrophil migration into the lungs, leading to respiratory dysfunction. Pre-administration of AL8810 further increased these features. Moreover, pre-treatment with AL8810 enhanced the HCl-induced expression of pro-inflammatory cytokines and neutrophil migratory factors in the lungs. Administration of HCl decreased the gene expression of lung surfactant proteins, which was further reduced by co-administration of AL8810. Administration of AL8810 also increased lung edema and reduced mRNA expression of epithelial sodium channel in the lungs, indicating that AL8810 reduced fluid clearance. Furthermore, AL8810 also increased lipopolysaccharide-induced expression of adhesion molecules such as intracellular adhesion molecule-1 and E-selectin in human umbilical vein endothelial cells. These results indicate that inhibition of FP receptors by AL8810 exacerbated HCl-induced ALI.

Interleukin-22 attenuates allergic airway inflammation in ovalbumin-induced asthma mouse model

BACKGROUND

Allergic asthma is a chronic airway inflammatory disease with a number of cytokines participating in its pathogenesis and progress. Interleukin (IL)-22, which is derived from lymphocytes, acts on epithelial cells and play a role in the chronic airway inflammation. However, the actual role of IL-22 in allergic asthma is still unclear. Therefore, we explored the effect of IL-22 on allergic airway inflammation and airway hyperresponsiveness (AHR) in an ovalbumin (OVA)-induced asthma mouse model.

METHODS

To evaluate the effect of IL-22 in an allergic asthma model, BALB/c mice were sensitized and challenged with OVA; then the recombinant mouse IL-22 was administered intranasally 24 h prior to each challenge. The IL-22 levels in lung homogenates and bronchoalveolar lavage fluid (BALF) were measured by enzyme linked immunosorbent assay, respectively. AHR was evaluated through indicators including airways resistance (Rrs), elastance (Ers) and compliance (Crs); the inflammatory cell infiltration was assessed by quantification of differential cells counts in BALF and lung tissues stained by hematoxylin and eosin (H&E); IL-22 specific receptors were determined by immunohistochemistry staining.

RESULTS

The concentration of IL-22 was significantly elevated in the OVA-induced mice compared with the control mice in lung homogenates and BALF. In the OVA-induced mouse model, IL-22 administration could significantly attenuate AHR, including Rrs, Ers and Crs, decrease the proportion of eosinophils in BALF and reduce inflammatory cell infiltration around bronchi and their concomitant vessels, compared with the OVA-induced group. In addition, the expression of IL-22RA1 and IL-10RB in the lung tissues of OVA-induced mice was significantly increased compared with the control mice, while it was dramatically decreased after the treatment with IL-22, but not completely attenuated in the IL-22-treated mice when compared with the control mice.

CONCLUSION

Interleukin-22 could play a protective role in an OVA-induced asthma model, by suppressing the inflammatory cell infiltration around bronchi and their concomitant vessels and airway hyperresponsiveness, which might associate with the expression of its heterodimer receptors. Thus, IL-22 administration might be an effective strategy to attenuate allergic airway inflammation.

Disease Tolerance during Viral-Bacterial Co-Infections

Disease tolerance has emerged as an alternative way, in addition to host resistance, to survive viral-bacterial co-infections. Disease tolerance plays an important role not in reducing pathogen burden, but in maintaining tissue integrity and controlling organ damage. A common co-infection is the synergy observed between influenza virus and Streptococcus pneumoniae that results in superinfection and lethality. Several host cytokines and cells have shown promise in promoting tissue protection and damage control while others induce severe immunopathology leading to high levels of morbidity and mortality. The focus of this review is to describe the host cytokines and innate immune cells that mediate disease tolerance and lead to a return to host homeostasis and ultimately, survival during viral-bacterial co-infection.

Emerging Role of Interleukins for the Assessment and Treatment of Liver Diseases

BACKGROUND

The most common liver diseases are fibrosis, alcoholic liver disease, non-alcoholic fatty disease, viral hepatitis, and hepatocellular carcinoma. These liver diseases account for approximately 2 million deaths per year worldwide, with cirrhosis accounting for 2.1% of the worldwide burden. The most widely used liver function tests for diagnosis are alanine transaminase, aspartate transaminase, serum proteins, serum albumin, and serum globulins, whereas antivirals and corticosteroids have been proven to be useful for the treatment of liver diseases. A major disadvantage of these diagnostic measures is the lack of specificity to a particular tissue or cell type, as these enzymes are common to one or more tissues. The major adverse effect of current treatment methods is drug resistance. To overcome these issues, interleukins have been investigated. The balance of these interleukins determines the outcome of an immune response. Interleukins are considered interesting therapeutic targets for the treatment of liver diseases. In this review, we summarize the current state of knowledge regarding interleukins in the diagnosis, treatment, and pathogenesis of different acute and chronic liver diseases.

OBJECTIVE

To understand the role of interleukins in the assessment and treatment of different types of liver diseases.

METHODS

A literature search was conducted using PubMed, Science Direct, and NCBI with the following keywords: Interleukins, Acute Liver Failure, Alcoholic Liver Disease, Non-Alcoholic Fatty Liver Disease, Liver Fibrosis, Hepatocellular Carcinoma, Inflammation, Liver injury, Hepatoprotective effect. Clinical trial data on these interleukins have been searched on Clinicaltrials.gov.

RESULTS

Existing literature and preclinical and clinical trial data demonstrate that interleukins play a crucial role in the pathogenesis of liver diseases.

CONCLUSION

Our findings indicate that IL-1, IL-6, IL-10, IL-17, IL-22, IL-35, and IL-37 are involved in the progression and control of various liver conditions via the regulation of cell signaling pathways. However, further investigation on the involvement of these interleukins is necessary for their use as a targeted therapy in liver diseases.

IL-22 Binding Protein (IL-22BP) in the Regulation of IL-22 Biology

Cytokines are powerful mediators of inflammation. Consequently, their potency is regulated in many ways to protect the host. Several cytokines, including IL-22, have coordinating binding proteins or soluble receptors that bind to the cytokine, block the interaction with the cellular receptor, and thus prevent cellular signaling. IL-22 is a critical cytokine in the modulation of tissue responses during inflammation and is highly upregulated in many chronic inflammatory disease patients, including those with psoriasis, rheumatoid arthritis, and inflammatory bowel disease (IBD). In healthy individuals, low levels of IL-22 are secreted by immune cells, mainly in the gastrointestinal (GI) tract. However, much of this IL-22 is likely not biologically active due to the high levels of IL-22 binding protein (IL-22BP) produced by intestinal dendritic cells (DCs). IL-22BP is a soluble receptor homolog that binds to IL-22 with greater affinity than the membrane spanning receptor. Much is known regarding the regulation and function of IL-22 in health and disease. However, less is known about IL-22BP. In this review, we will focus on IL-22BP, including its regulation, role in IL-22 biology and inflammation, and promise as a therapeutic. IL-22 can be protective or pathogenic, depending on the context of inflammation. IL-22BP also has divergent roles. Ongoing and forthcoming studies will expand our knowledge of IL-22BP and IL-22 biology, and suggest that IL-22BP holds promise as a way to regulate IL-22 biology in patients with chronic inflammatory disease.

Profiling Tryptophan Catabolites of Human Gut Microbiota and Acute-Phase Protein Levels in Neonatal Dried Blood Specimens

National screening programs use dried blood specimens to detect metabolic disorders or aberrant protein functions that are not clinically evident in the neonatal period. Similarly, gut microbiota metabolites and immunological acute-phase proteins may reveal latent immune aberrations. Microbial metabolites interact with xenobiotic receptors (i.e., aryl hydrocarbon and pregnane-X) to maintain gastrointestinal tissue health, supported by acute-phase proteins, functioning as sensors of microbial immunomodulation and homeostasis. The delivery (vaginal or cesarean section) shapes the microbial colonization, which substantially modulates both the immune system’s response and mucosal homeostasis. This study profiled microbial metabolites of the kynurenine and tryptophan pathway and acute-phase proteins in 134 neonatal dried blood specimens. We newly established neonatal blood levels of microbial xenobiotic receptors ligands (i.e., indole-3-aldehyde, indole-3-butyric acid, and indole-3-acetamide) on the second day of life. Furthermore, we observed diverse microbial metabolic profiles in neonates born vaginally and via cesarean section, potentially due to microbial immunomodulatory influence. In summary, these findings suggest the supportive role of human gut microbiota in developing and maintaining immune system homeostasis.

Duck Interleukin-22: Identification and Expression Analysis in Riemerella anatipestifer Infection

Riemerella anatipestifer is one of the most devastating pathogens affecting the global duck farms. Infection is involved in secretion of proinflammatory cytokines, including interleukin- (IL-) 17A. During the immune response to infection, IL-22 and IL-17A are often produced concurrently and at high levels in inflamed tissues. Little is known about duck IL-22 (duIL-22) during R. anatipestifer infection. We describe the characterization of duIL-22 and its mRNA expression analysis in splenic lymphocytes and macrophages treated with heat-killed R. anatipestifer and in the spleens and livers of R. anatipestifer-infected ducks. Full-length cDNA of duIL-22 encoded 197 amino acids. The deduced amino acid sequence of duIL-22 shared a 30.4-40.5% similarity with piscine counterparts, 57.4-60.1% with mammalian homologs, and 93.4% similarity to the chicken. Duck IL-22 mRNA expression level was relatively high in the skin of normal ducks. It was increased in mitogen-stimulated splenic lymphocytes and in killed R. anatipestifer-activated splenic lymphocytes and macrophages. Compared with healthy ducks, IL-22 transcript expression was significantly upregulated in the livers and spleens on days 1 and 4 postinfection, but not on day 7. IL-17A was significantly increased in the spleens only on day 4 postinfection and in the livers at all time points. When splenic lymphocytes were stimulated with heat-killed R. anatipestifer, CD4+ cells predominantly produced IL-22 while IL-17A was expressed both by CD4+ and CD4- cells. These results suggested that IL-22 and IL-17A are likely expressed in different cell types during R. anatipestifer infection.

Immunological Networks Defining the Heterogeneity of Inflammatory Bowel Diseases

Current practice in IBD is to classify patients based on clinical signs and symptoms and provide treatments accordingly. However, the response of IBD patients to available treatments is highly variable, highlighting clinically significant heterogeneity among patients. Thus, more accurate patient stratification is urgently needed to more effectively target therapeutic interventions to specific patients. Here we review the degree of heterogeneity in IBD, discussing how the microbiota, genetics, and immune system may contribute to the variation among patients. We highlight how molecular heterogeneity may relate to clinical phenotype, but in other situations may be independent of clinical phenotype, encouraging future studies to fill the gaps. Finally, we discuss novel stratification methodologies as a foundation for precision medicine, in particular a novel stratification strategy based on conserved genes across species. All of these dimensions of heterogeneity have potential to provide strategies for patient stratification and move IBD practice towards personalised medicine.

The role of Th22 cells, from tissue repair to cancer progression

CD4⁺ T helper (Th) cells play a significant role in modulating host defense. In the presence of lineage specific cytokine cocktail, Naive CD4⁺ T cells can differentiate into several categories with distinct cytokines profile and effector functions. Th22 cells are a recently identified subset of CD4⁺ T cell, which differentiate from Naive CD4⁺ T in the presence of IL-6 and TNF-α. Th22 characterized by the production of interleukin-22 (IL-22) and expression of aryl hydrocarbon receptor (AHR). The main function of Th22 cells is to participate in mucosal defense, tissue repair, and wound healing. However, controversial data have shown that overexpression of IL-22 can lead to pathological changes under inflammatory conditions and tumor progression. This review summarizes our knowledge about the role of Th22 and IL-22 cells in tumor progression through induction of inflammation.

The Role of In Vitro Detection of Drug-Specific Mediator-Releasing Cells to Diagnose Different Phenotypes of Severe Cutaneous Adverse Reactions

PROPOSE

The purpose of this study was to investigate panels of enzyme-linked immunospot assays (ELISpot) to detect drug-specific mediator releasing cells for confirming culprit drugs in severe cutaneous adverse reactions (SCARs).

METHODS

Frequencies of drug-induced interleukin-22 (IL-22)-, interferon-gamma (IFN-γ)-, and granzyme-B (GrB)-releasing cells were measured by incubating peripheral blood mononuclear cells (PBMCs) from SCAR patients with the culprit drugs. Potential immunoadjuvants were supplemented to enhance drug-induced mediator responses.

RESULTS

Twenty-seven patients, including 9 acute generalized exanthematous pustulosis (AGEP), 10 drug reactions with eosinophilia and systemic symptoms, and 8 Stevens-Johnson syndrome and toxic epidermal necrolysis (SJS/TEN) were recruited. The average frequencies of drug-induced IL-22-, IFN-γ-, and GrB-releasing cells were 35.5±16.3, 33.0±7.1, and 164.8±43.1 cells/million PBMCs, respectively. The sensitivity of combined IFN-γ/IL-22/GrB ELISpot was higher than that of IFN-γ ELISpot alone for culprit drug detection in all SCAR subjects (77.8% vs 51.9%, P < 0.01). The measurement of drug-induced IL-22- and IFN-γ releasing cells confirmed the culprit drugs in 77.8% of AGEP. The measurement of drug-induced IFN-γ- and GrB-releasing cells confirmed the culprit drugs in 62.5% of SJS/TEN. Alpha-galactosylceramide supplementation significantly increased the frequencies of drug-induced IFN-γ releasing cells.

CONCLUSION

The measurement of drug-induced IFN-γ-releasing cells is the key for identifying culprit drugs. The additional measurement of drug-induced IL-22-releasing cells enhances ELISpot sensitivity to identify drug-induced AGEP, while the measurement of drug-induced GrB-releasing cells could have a role in SJS/TEN. ELISpot sensitivity might be improved by supplementary alpha-galactosylceramide.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02574988.

Interleukin-22 Deficiency Contributes to Dextran Sulfate Sodium-Induced Inflammation in Japanese Medaka, Oryzias latipes

Mucosal tissue forms the first line of defense against pathogenic microorganisms. Cellular damage in the mucosal epithelium may induce the interleukin (IL)-22-related activation of many immune cells, which are essential for maintaining the mucosal epithelial barrier. A previous study on mucosal immunity elucidated that mammalian IL-22 contributes to mucus and antimicrobial peptides (AMPs) production and anti-apoptotic function. IL-22 has been identified in several teleost species and is also induced in response to bacterial infections. However, the roles of IL-22 in teleost immunity and mucus homeostasis are poorly understood. In this study, Japanese medaka (Oryzias latipes) was used as a model fish. The medaka il22, il22 receptor A1 (il22ra1), and il22 binding protein (il22bp) were cloned and characterized. The expression of medaka il22, il22ra1, and il22bp in various tissues was measured using qPCR. These genes were expressed at high levels in the mucosal tissues of the intestines, gills, and skin. The localization of il22 and il22bp mRNA in the gills and intestines was confirmed by in situ hybridizations. Herein, we established IL-22-knockout (KO) medaka using the CRISPR/Cas9 system. In the IL-22-KO medaka, a 4-bp deletion caused a frameshift in il22. To investigate the genes subject to IL-22-dependent regulation, we compared the transcripts of larval medaka between wild-type (WT) and IL-22-KO medaka using RNA-seq and qPCR analyses. The comparison was performed not only in the naïve state but also in the dextran sulfate sodium (DSS)-exposed state. At the transcriptional level, 368 genes, including immune genes, such as those encoding AMPs and cytokines, were significantly downregulated in IL-22-KO medaka compared that in WT medaka in naïve states. Gene ontology analysis revealed that upon DSS stimulation, genes associated with cell death, acute inflammatory response, cell proliferation, and others were upregulated in WT medaka. Furthermore, in DSS-stimulated IL-22-KO medaka, wound healing was delayed, the number of apoptotic cells increased, and the number of goblet cells in the intestinal epithelium decreased. These results suggested that in medaka, IL-22 is important for maintaining intestinal homeostasis, and the disruption of the IL-22 pathway is associated with the exacerbation of inflammatory pathology, as observed for mammalian IL-22.

Relationship between Th17 immune response and cancer

Cancer is the second leading cause of death worldwide and epidemiological projections predict growing cancer mortality rates in the next decades. Cancer has a close relationship with the immune system and, although Th17 cells are known to play roles in the immune response against microorganisms and in autoimmunity, studies have emphasized their roles in cancer pathogenesis. The Th17 immune response profile is involved in several types of cancer including urogenital, respiratory, gastrointestinal, and skin cancers. This type of immune response exerts pro and antitumor functions through several mechanisms, depending on the context of each tumor, including the protumor angiogenesis and exhaustion of T cells and the antitumor recruitment of T cells and neutrophils to the tumor microenvironment. Among other factors, the paradoxical behavior of Th17 cells in this setting has been attributed to its plasticity potential, which makes possible their conversion into other types of T cells such as Th17/Treg and Th17/Th1 cells. Interleukin (IL)-17 stands out among Th17-related cytokines since it modulates pathways and interacts with other cell profiles in the tumor microenvironment, which allow Th17 cells to prevail in tumors. Moreover, the IL-17 is able to mediate pro and antitumor processes that influence the development and progression of various cancers, being associated with variable clinical outcomes. The understanding of the relationship between the Th17 immune response and cancer as well as the singularities of carcinogenic processes in each type of tumor is crucial for the identification of new therapeutic targets.

Attenuation of apoptotic cell detection triggers thymic regeneration after damage

The thymus, which is the primary site of T cell development, is particularly sensitive to insult but also has a remarkable capacity for repair. However, the mechanisms orchestrating regeneration are poorly understood, and delayed repair is common after cytoreductive therapies. Here, we demonstrate a trigger of thymic regeneration, centered on detecting the loss of dying thymocytes that are abundant during steady-state T cell development. Specifically, apoptotic thymocytes suppressed production of the regenerative factors IL-23 and BMP4 via TAM receptor signaling and activation of the Rho-GTPase Rac1, the intracellular pattern recognition receptor NOD2, and micro-RNA-29c. However, after damage, when profound thymocyte depletion occurs, this TAM-Rac1-NOD2-miR29c pathway is attenuated, increasing production of IL-23 and BMP4. Notably, pharmacological inhibition of Rac1-GTPase enhanced thymic function after acute damage. These findings identify a complex trigger of tissue regeneration and offer a regenerative strategy for restoring immune competence in patients whose thymic function has been compromised.

Colonizing Microbes, IL-10 and IL-22: Keeping the Peace at the Mucosal Surface

Our world is filled with microbes. Each multicellular organism has developed ways to interact with this microbial environment. Microbes do not always pose a threat; they can contribute to many processes that benefit the host. Upon colonization both host and microbes adapt resulting in dynamic ecosystems in different host niches. Regulatory processes develop within the host to prevent overt inflammation to beneficial microbes, yet keeping the possibility to respond when pathogens attempt to adhere and invade tissues. This review will focus on microbial colonization and the early (innate) host immune response, with special emphasis on the microbiota-modifying roles of IL-10 and IL-22 in the intestine. IL-10 knock out mice show an altered microbial composition, and spontaneously develop enterocolitis over time. IL-22 knock out mice, although not developing enterocolitis spontaneously, also have an altered microbial composition and increase of epithelial-adherent bacteria, mainly caused by a decrease in mucin and anti-microbial peptide production. Recently interesting links have been found between the IL-10 and IL-22 pathways. While IL-22 can function as a regulatory cytokine at the mucosal surface, it also has inflammatory roles depending on the context. For example, lack of IL-22 in the IL-10–/– mice model prevents spontaneous colitis development. Additionally, the reduced microbial diversity observed in IL-10–/– mice was also reversed in IL-10/IL-22 double mutant mice (Gunasekera et al., 2020). Since in early life, host immunity develops in parallel and in interaction with colonizing microbes, there is a need for future studies that focus on the effect of the timing of colonization in relation to the developmental phase of the host. To illustrate this, examples from zebrafish research will be compared with studies performed in mammals. Since zebrafish develop from eggs and are directly exposed to the outside microbial world, timing of the development of host immunity and subsequent control of microbial composition, is different from mammals that develop in utero and only get exposed after birth. Likewise, colonization studies using adult germfree mice might yield different results from those using neonatal germfree mice. Lastly, special emphasis will be given to the need for host genotype and environmental (co-housing) control of experiments.

Toward a universal influenza virus vaccine: Some cytokines may fulfill the request

The influenza virus annually causes widespread damages to the health and economy of the global community. Vaccination is currently the most crucial strategy in reducing the number of patients. Genetic variations, the high diversity of pandemic viruses, and zoonoses make it challenging to select suitable strains for annual vaccine production. If new pandemic viruses emerge, it will take a long time to produce a vaccine according to the new strains. In the present study, intending to develop a universal influenza vaccine, new bicistronic DNA vaccines were developed that expressed NP or NPm antigen with one of modified IL-18/ IL-17A/ IL-22 cytokine adjuvants. NPm is a mutant form of the antigen that has the ability for cytoplasmic accumulation. In order to investigate and differentiate the role of each of the components of Th1, Th2, Th17, and Treg cellular immune systems in the performance of vaccines, Treg competent and Treg suppressed mouse groups were used. Mice were vaccinated with Foxp3-FC immunogen to produce Treg suppressed mouse groups. The potential of the vaccines to stimulate the immune system was assessed by IFN-γ/IL-17A Dual FluoroSpot. The vaccine's ability to induce humoral immune response was determined by measuring IgG1, IgG2a, and IgA-specific antibodies against the antigen. Kinetics of Th1, Th2, and Th17 cellular immune responses after vaccination, were assessed by evaluating the expression changes of IL-17A, IFN-γ, IL-18, IL-22, IL-4, and IL-2 cytokines by semi-quantitative real-time RT-PCR. To assess the vaccines' ability to induce heterosubtypic immunity, challenge tests with homologous and heterologous viruses were performed and then the virus titer was measured in the lungs of animals. Evaluation of the data obtained from this study showed that the DNA-vaccines coding NPm have more ability to induces a potent cross-cellular immune response and protective immunity than DNA-vaccines coding NP. Although the use of IL-18/ IL-17A/ IL-22 genetic adjuvants enhanced immune responses and protective immunity, Administration of NPm in combination with modified IL-18 (Igk-mIL18-IgFC) induced the most effective immunity in Treg competent mice group.

Lymphocytes: Versatile Participants in Acute Kidney Injury and Progression to Chronic Kidney Disease

Background: Acute kidney injury (AKI) remains a major global public health concern due to its high morbidity and mortality. The progression from AKI to chronic kidney disease (CKD) makes it a scientific problem to be solved. However, it is with lack of effective treatments. Summary: Both innate and adaptive immune systems participate in the inflammatory process during AKI, and excessive or dysregulated immune responses play a pathogenic role in renal fibrosis, which is an important hallmark of CKD. Studies on the pathogenesis of AKI and CKD have clarified that renal injury induces the production of various chemokines by renal parenchyma cells or resident immune cells, which recruits multiple-subtype lymphocytes in circulation. Some infiltrated lymphocytes exacerbate injury by proinflammatory cytokine production, cytotoxicity, and interaction with renal resident cells, which constructs the inflammatory environment and induces further injury, even death of renal parenchyma cells. Others promote tissue repair by producing protective cytokines. In this review, we outline the diversity of these lymphocytes and their mechanisms to regulate the whole pathogenic stages of AKI and CKD; discuss the chronological responses and the plasticity of lymphocytes related to AKI and CKD progression; and introduce the potential therapies targeting lymphocytes of AKI and CKD, including the interventions of chemokines, cytokines, and lymphocyte frequency regulation in vivo, adaptive transfer of ex-expanded lymphocytes, and the treatments of gut microbiota or metabolite regulations based on gut-kidney axis. Key Message: In the process of AKI and CKD, T helper (Th) cells, innate, and innate-like lymphocytes exert mainly pathogenic roles, while double-negative T (DNT) cells and regulatory T cells (Tregs) are confirmed to be protective. Understanding the mechanisms by which lymphocytes mediate renal injury and renal fibrosis is necessary to promote the development of specific therapeutic strategies to protect from AKI and prevent the progression of CKD.

Novel Insights Into the Mechanism of GVHD-Induced Tissue Damage

Prophylaxis for and treatment of graft-versus-host disease (GVHD) are essential for successful allogeneic hematopoietic stem cell transplantation (allo-SCT) and mainly consist of immunosuppressants such as calcineurin inhibitors. However, profound immunosuppression can lead to tumor relapse and infectious complications, which emphasizes the necessity of developing novel management strategies for GVHD. Emerging evidence has revealed that tissue-specific mechanisms maintaining tissue homeostasis and promoting tissue tolerance to combat GVHD are damaged after allo-SCT, resulting in exacerbation and treatment refractoriness of GVHD. In the gastrointestinal tract, epithelial regeneration derived from intestinal stem cells (ISCs), a microenvironment that maintains healthy gut microbiota, and physical and chemical mucosal barrier functions against pathogens are damaged by conditioning regimens and/or GVHD. The administration of growth factors for cells that maintain intestinal homeostasis, such as interleukin-22 (IL-22) for ISCs, R-spondin 1 (R-Spo1) for ISCs and Paneth cells, and interleukin-25 (IL-25) for goblet cells, mitigates murine GVHD. In this review, we summarize recent advances in the understanding of GVHD-induced tissue damage and emerging strategies for the management of GVHD.

Induction of IL-22-Producing CD4+ T Cells by Segmented Filamentous Bacteria Independent of Classical Th17 Cells

The intestinal microbiota modulates IL-22 production in the intestine, including the induction of IL-22-producing CD4+ T helper cells. Which specific bacteria are responsible for the induction of these cells is less well understood. Here, we demonstrate through the use of novel gnotobiotic knock-in reporter mice that segmented filamentous bacteria (SFB), which are known for their ability to induce Th17 cells, also induce distinct IL-17A negative CD4+ T cell populations in the intestine. A subset of these cells instead produces IL-22 upon restimulation ex vivo and also during enteric infections. Furthermore, they produce a distinct set of cytokines compared to Th17 cells including the differential expression of IL-17F and IFN-γ. Importantly, genetic models demonstrate that these cells, presumably Th22 cells, develop independently of intestinal Th17 cells. Together, our data identifies that besides Th17, SFB also induces CD4+ T cell populations, which serve as immediate source of IL-22 during intestinal inflammation.

Recombinant IL-22 promotes protection in a murine model of Aspergillus flavus keratitis and mediates host immune responses in human corneal epithelial cells

Aspergillus flavus is a leading cause of corneal infections in India and worldwide, resulting in severe visual impairment. We studied the host immune response towards A. flavus in immortalised human corneal epithelial cells (HCEC) and found increased expression of Toll-like receptors, antimicrobial peptides and proinflammatory cytokines like IL-6 and IL-8. Differential expressions of antimicrobial peptides were determined in corneal scrapings from A. flavus keratitis patients with significantly increased expression of LL-37, S100A12 and RNase 7. Increased levels of IL-22 expression were observed both in patients with A. flavus keratitis and in experimental mice model of corneal infections along with IL-17, IL-23 and IL-18. IL-22 is an important mediator of inflammation during microbial infections, and acts primarily on fibroblasts and epithelial cells. We observed constitutive expression of IL-22 receptors in HCEC, and IL-22 mediated activation of NF-κB, MAPK pathways and STAT3, along with increased expression of antimicrobial peptides in these cells. IL-22 also efficiently lessened cell deaths in corneal epithelial cells during A. flavus infection in vitro. Furthermore, recombinant IL-22 reduced fungal burden and corneal opacity in an experimental murine model of A. flavus keratitis.

Interleukin (IL)-13/IL-22/IL-31 skewing within the skin-homing T-cell population in papuloerythroderma

Papuloerythroderma (PEO) is a representative form of senile erythroderma with an unclear pathogenesis. This study aimed to characterize the T-cell phenotypes responsible for the pathogenesis of PEO. Cytokine profiles and cutaneous lymphocyte antigen (CLA) expression on circulating T lymphocytes in patients with PEO were simultaneously analyzed using flow cytometry. The patients with PEO showed significantly higher circulating interleukin (IL)-4-, IL-13-, IL-22-, and IL-31-producing CD4+ and CD8+ T-cell levels than healthy subjects. However, their levels significantly decreased after remission of PEO. No difference was observed in the proportions of circulating interferon (IFN)-γ- and IL-17-producing CD4+ and CD8+ T cells between the patients with PEO and healthy subjects. In particular, the proportion of circulating IL-4-, IL-13-, IL-22-, and IL-31-producing CD4+ and CD8+ T cells was much higher in the CLA+ subset than in the CLA- subset. There was a positive correlation between IL-13-, IL-22-, and IL-31-producing CD4+ T cells and the disease severity score of PEO. Moreover, a positive correlation was also observed between the proportion of IL-22- or IL-31-producing cells and circulating IL-13-producing cells in both CD4+ and CD8+ T cells, and approximately 50% of both IL-22- and IL-31-producing CD4+ and CD8+ T cells coproduced IL-13. IL-13/IL-22/IL-31 skewing within the skin-homing T-cell population may be involved in the pathogenesis of PEO.

Intestinal immunoregulation: lessons from human mendelian diseases

The mechanisms that maintain intestinal homeostasis despite constant exposure of the gut surface to multiple environmental antigens and to billions of microbes have been scrutinized over the past 20 years with the goals to gain basic knowledge, but also to elucidate the pathogenesis of inflammatory bowel diseases (IBD) and to identify therapeutic targets for these severe diseases. Considerable insight has been obtained from studies based on gene inactivation in mice as well as from genome wide screens for genetic variants predisposing to human IBD. These studies are, however, not sufficient to delineate which pathways play key nonredundant role in the human intestinal barrier and to hierarchize their respective contribution. Here, we intend to illustrate how such insight can be derived from the study of human Mendelian diseases, in which severe intestinal pathology results from single gene defects that impair epithelial and or hematopoietic immune cell functions. We suggest that these diseases offer the unique opportunity to study in depth the pathogenic mechanisms leading to perturbation of intestinal homeostasis in humans. Furthermore, molecular dissection of monogenic intestinal diseases highlights key pathways that might be druggable and therapeutically targeted in common forms of IBD.

T-helper 22 cells develop as a distinct lineage from Th17 cells during bacterial infection and phenotypic stability is regulated by T-bet

CD4+ T-helper 22 (Th22) cells are a phenotypically distinct lymphocyte subset that produces high levels of interleukin (IL)-22 without co-production of IL-17A. However, the developmental origin and lineage classification of Th22 cells, their interrelationship to Th17 cells, and potential for plasticity at sites of infection and inflammation remain largely undefined. An improved understanding of the mechanisms underpinning the outgrowth of Th22 cells will provide insights into their regulation during homeostasis, infection, and disease. To address this knowledge gap we generated 'IL-17A-fate-mapping IL-17A/IL-22 reporter transgenic mice' and show that Th22 cells develop in the gastrointestinal tract and lung during bacterial infection without transitioning via an Il17a-expressing intermediate, although in some compartments alternative transition pathways exist. Th22-cell development was not dependent on T-bet; however, this transcription factor functioned as a promiscuous T-cell-intrinsic regulator of IL-17A and IL-22 production, in addition to regulating the outgrowth, phenotypic stability, and plasticity of Th22 cells. Thus, we demonstrate that at sites of mucosal bacterial infection Th22 cells develop as a distinct lineage independently of Th17 cells; though both lineages exhibit bidirectional phenotypic flexibility within infected tissues and their draining lymph nodes, and that T-bet plays a critical regulatory role in Th22-cell function and identity.

Cytokines and Chemokines Involved in Osteoarthritis Pathogenesis

Osteoarthritis is a common cause of disability worldwide. Although commonly referred to as a disease of the joint cartilage, osteoarthritis affects all joint tissues equally. The pathogenesis of this degenerative process is not completely understood; however, a low-grade inflammation leading to an imbalance between anabolic and katabolic processes is a well-established factor. The complex network of cytokines regulating these processes and cell communication has a central role in the development and progression of osteoarthritis. Concentrations of both proinflammatory and anti-inflammatory cytokines were found to be altered depending on the osteoarthritis stage and activity. In this review, we analyzed individual cytokines involved in the immune processes with an emphasis on their function in osteoarthritis.

Regulatory roles of MicroRNA in shaping T cell function, differentiation and polarization

T lymphocytes are an integral component of adaptive immunity with pleotropic effector functions. Impairment of T cell activity is implicated in various immune pathologies including autoimmune diseases, AIDS, carcinogenesis, and periodontitis. Evidently, T cell differentiation and function are under robust regulation by various endogenous factors that orchestrate underlying molecular pathways. MicroRNAs (miRNA) are a class of noncoding, regulatory RNAs that post-transcriptionally control multiple mRNA targets by sequence-specific interaction. In this article, we will review the recent progress in our understanding of miRNA-gene networks that are uniquely required by specific T cell effector functions and provide miRNA-mediated mechanisms that govern the fate of T cells. A subset of miRNAs may act in a synergistic or antagonistic manner to exert functional suppression of genes and regulate pathways that control T cell activation and differentiation. Significance of T cell-specific miRNAs and their dysregulation in immune-mediated diseases is discussed. Exosome-mediated horizontal transfer of miRNAs from antigen presenting cells (APCs) to T cells and from one T cell to another T cell subset and their impact on recipient cell functions is summarized.

Interleukin-22: a potential therapeutic target in atherosclerosis

BACKGROUND

Atherosclerosis is recognized as a chronic immuno-inflammatory disease that is characterized by the accumulation of immune cells and lipids in the vascular wall. In this review, we focus on the latest advance regarding the regulation and signaling pathways of IL-22 and highlight its impacts on atherosclerosis.

MAIN BODY

IL-22, an important member of the IL-10 family of cytokines, is released by cells of the adaptive and innate immune system and plays a key role in the development of inflammatory diseases. The binding of IL-22 to its receptor complex can trigger a diverse array of downstream signaling pathways, in particular the JAK/STAT, to induce the expression of chemokines and proinflammatory cytokines. Recently, numerous studies suggest that IL-22 is involved in the pathogenesis of atherosclerosis by regulation of VSMC proliferation and migration, angiogenesis, inflammatory response, hypertension, and cholesterol metabolism.

CONCLUSION

IL-22 promotes the development of atherosclerosis by multiple mechanisms, which may be a promising therapeutic target in the pathogenesis of atherosclerosis.

Interaction Between the Microbiota, Epithelia, and Immune Cells in the Intestine

The gastrointestinal tract harbors numerous commensal bacteria, referred to as the microbiota, that benefit host health by digesting dietary components and eliminating pathogens. The intestinal microbiota maintains epithelial barrier integrity and shapes the mucosal immune system, balancing host defense and oral tolerance with microbial metabolites, components, and attachment to host cells. To avoid aberrant immune responses, epithelial cells segregate the intestinal microbiota from immune cells by constructing chemical and physical barriers, leading to the establishment of host-commensal mutualism. Furthermore, intestinal immune cells participate in the maintenance of a healthy microbiota community and reinforce epithelial barrier functions. Perturbations of the microbiota composition are commonly observed in patients with autoimmune diseases and chronic inflammatory disorders. An understanding of the intimate interactions between the intestinal microbiota, epithelial cells, and immune cells that are crucial for the maintenance of intestinal homeostasis might promote advances in diagnostic and therapeutic approaches for various diseases.

Graft-versus-host disease: a disorder of tissue regeneration and repair

Regenerative failure at barrier surfaces and maladaptive repair leading to fibrosis are hallmarks of graft-versus-host disease (GVHD). Although immunosuppressive treatment can control inflammation, impaired tissue homeostasis leads to prolonged organ damage and impaired quality of life. In this Spotlight article, we review recent research that addresses the critical failures in tissue regeneration and repair that underpin treatment-resistant GVHD. We highlight current interventions designed to overcome these defects and provide our assessment of the future therapeutic landscape.

The post-hematopoietic cell transplantation microbiome: relationships with transplant outcome and potential therapeutic targets

Microbiota injury occurs in many patients undergoing allogeneic hematopoietic cell transplantation, likely as a consequence of conditioning regimens involving chemo- and radiotherapy, the widespread use of both prophylactic and therapeutic antibiotics, and profound dietary changes during the peri-transplant period. Peri-transplant dysbiosis is characterized by a decrease in bacterial diversity, loss of commensal bacteria and single-taxon domination (e.g., with Enterococcal strains). Clinically, deviation of the post-transplant microbiota from a normal, high-diversity, healthy state has been associated with increased risk of bacteremia, development of graft-versus-host disease and decreases in overall survival. A number of recent clinical trials have attempted to target the microbiota in allogeneic hematopoietic cell transplantation patients via dietary interventions, selection of therapeutic antibiotics, administration of pre- or pro-biotics, or by performing fecal microbiota transplantation. These strategies have yielded promising results but the mechanisms by which these interventions influence transplant-related complications remain largely unknown. In this review we summarize the current approaches to targeting the microbiota, discuss potential underlying mechanisms and highlight the key outstanding areas that require further investigation in order to advance microbiota- targeting therapies.

Interleukins in cancer: from biology to therapy

Interleukins and associated cytokines serve as the means of communication for innate and adaptive immune cells as well as non-immune cells and tissues. Thus, interleukins have a critical role in cancer development, progression and control. Interleukins can nurture an environment enabling and favouring cancer growth while simultaneously being essential for a productive tumour-directed immune response. These properties of interleukins can be exploited to improve immunotherapies to promote effectiveness as well as to limit side effects. This Review aims to unravel some of these complex interactions.

Specific bioactivity of IL-22 in intestinal cells as revealed by the expression of IL-22RA1 in Mandarin fish, Siniperca chuatsi

IL-22, a multifunctional cytokine, acts as an important regulator in host immunity in mammals. IL-22 homologues have been characterized in several species of fish, with its expression found in multiple tissues/cells in fish, but its target cells have not been fully analyzed. In the present research, different organ/tissue isolated cells were examined for the expression of IL-22 and the induced IL-22 responses in mandarin fish. The mandarin fish IL-22 was found to be expressed in all these tested cells with high basal expression in intestinal cells. The HKLs showed low basal expression but significant increase in expression of IL-22 after LPS treatment or bacterial infection. Only intestinal cells showed response to IL-22 by enhanced expression of hepcidin, LEAP2 and IL-22BP, with unresponsiveness observed in other tested cells, which indicated the cell-specificity of IL-22 bioactivity in mandarin fish. One of the heterodimeric receptor components for IL-22, the IL-22RA1, was cloned in mandarin fish, with four tandem fibronectin type III (FNIII) domains identified in its extracellular part. IL-22RA1 exhibited an intestinal cell-specific expression pattern, although another receptor component of IL-22, IL-10R2, displayed constitutive expressions in all these tested cells. The present study reveals that the mandarin fish IL-22 exhibits its bioactivity in a cell-specific manner in intestinal cells, which is reflected in the restrictive expression of its receptor unit, IL-22RA1.

The Assessment of IL-21 and IL-22 at the mRNA Level in Tumor Tissue and Protein Concentration in Serum and Peritoneal Fluid in Patients with Ovarian Cancer

The aim of the analysis was for the first time to assess the expression of genes encoding IL-21 and IL-22 at the mRNA level in ovarian tumor specimens and the concentration of these parameters in serum and peritoneal fluid in patients with ovarian serous cancer. The levels of IL-21 and IL-22 transcripts were evaluated with the use of the real-time RT-qPCR. Enzyme-linked immunosorbent assay (ELISA) was used to determine the concentration of proteins. Quantitative analysis of IL-21 gene mRNA in the tumor tissue showed the highest activity in the G1 degree of histopathological differentiation and was higher in G1 compared to the control group. The concentration of IL-21 and IL-22 in the serum and in the peritoneal fluid of women with ovarian cancer varied depending on the degree of histopathological differentiation of the cancer and showed statistical variability compared to controls. The conducted studies have shown that the local and systemic changes in the immune system involving IL-21 and IL-22 indicate the participation of these parameters in the pathogenesis of ovarian cancer, and modulation in the IL-21/IL-22 system may prove useful in the development of new diagnostic and therapeutic strategies used in patients, which require further research.

Role of Th22 Cells in the Pathogenesis of Autoimmune Diseases

Upon antigenic stimulation, naïve CD4+T cells differentiate into different subsets and secrete various cytokines to exert biological effects. Th22 cells, a newly identified CD4+T cell subset,are distinct from the Th1, Th2 and Th17 subsets. Th22 cells secrete certain cytokines such as IL-22, IL-13 and TNF-α, but not others, such as IL-17, IL-4, or interferon-γ (IFN-γ), and they express chemokine receptors CCR4, CCR6 and CCR10. Th22 cells were initially found to play a role in skin inflammatory diseases, but recent studies have demonstrated their involvement in the development of various autoimmune diseases. Here, we review research advances in the origin, characteristics and effector mechanisms of Th22 cells, with an emphasis on the role of Th22 cells and their main effector cytokine IL-22 in the pathogenesis of autoimmune diseases. The findings presented here may facilitate the development of new therapeutic strategies for targeting these diseases.

T cell cytokines in the diagnostic of early-onset sepsis

BACKGROUND

Early-onset sepsis (EOS) remains a substantial cause of morbidity and mortality among neonates. Yet, currently available biological parameters have not proven to be accurate enough to predict EOS reliably. This study aimed to determine serum concentrations of 13 cytokines in umbilical cord blood and evaluate their diagnostic value for EOS.

METHODS

A prospective single-center study that included analysis of umbilical cord blood of term and preterm neonates who were born from March 2017 to November 2017. Using ELISA analysis, 13 cytokines were simultaneously quantified and correlated with the development of EOS.

RESULTS

Four hundred and seventy-four neonates were included, of which seven met the criteria for culture-positive EOS. Interleukin (IL)-6 (p < 0.001), IL-9 (p = 0.003), and IL-21 (p < 0.001) were significantly increased in neonates with EOS compared to controls. Sensitivity and specificity for IL-6, IL-9, and IL-21 at the defined cut-off points were 85.7 and 77.3%, 71.4 and 62.5%, and 71.4 and 52.0%, respectively.

CONCLUSIONS

In neonates with EOS, IL-9 and IL-21 are significantly elevated and may be employed in the diagnostic of EOS. However, diagnostic accuracy remains lower than with IL-6. Values of 13 T cell cytokines may be used as reference values for future studies in neonates.

IMPACT

Interleukin-9 (IL-9) and interleukin-21 (IL-21) are significantly elevated in neonates with early-onset sepsis. IL-9 and IL-21 have been shown to play a specific role in neonatal sepsis. Neonatal reference values were generated for several cytokines. IL-9 and IL-21 might be attractive biomarkers for neonatal sepsis in future. This study is likely to promote further research in this area. Values of several T cell cytokines may be used as reference values for future studies in neonates.

IL-26 promotes the pathogenesis of malignant pleural effusion by enhancing CD4+ IL-22+ T-cell differentiation and inhibiting CD8+ T-cell cytotoxicity

IL-26 is a newly discovered IL-10 cytokine family member mainly secreted by Th17 cells. However, the relationship between IL-26 and lung cancer remains unclear. The present study reported that IL-26 is involved in the production and promotion of malignant pleural effusion (MPE) for the first time. The concentrations of IL-26 and several Th17-related cytokines in MPE and peripheral blood (PB) from MPE patients were measured. IL-26, IL-10, and IL-6 were elevated in MPE compared to PB. The cell resource of IL-26 was primary Th17 cells measured by flow cytometry, whereas Tc17 cells and macrophages could also contribute to higher concentration of IL-26 in MPE. Abundant IL-6 and IL-23 in MPE could promote the frequency of IL-26 expressed by CD4+ T cells through phosphorylating STAT3 signaling pathway and promoting the expression of a specific Th17 lineage marker RORγt subsequently. IL-26 could selectively increase Th22 proportion through up-regulating the percentage of Ki-67 expressed by CD4+ T cells and the expression of IL-22 secreted by memory CD4+ T cells. In addition, IL-26 could decrease secretion of granzyme B. The tumor-killing activity of CD8+ T cells were inhibited as well when cocultured with malignant cells. Furthermore, the accumulation of IL-26 protein in MPE predicted poor patient survival. In summary, our results indicated that IL-26 was involved in the pathogenesis of MPE by exerting its impacts on both CD4+ T cells and CD8+ T cells.

Interleukine-22 gene variants are associated with susceptibility to visceral leishmaniasis

Visceral leishmaniasis (VL) is an infectious disease caused by an intracellular protozoan belonging to Leishmania species. Interleukin (IL)-22 plays an important role in inflammatory response, chemotaxis, regulation of cellular proliferation and tissue repair. Considering the role of IL-22 in control of leishmaniasis and the effect of its single nucleotide polymorphisms (SNPs) on respective function and production, this study aimed to investigate the probable association of IL-22 SNPs with VL. The study was carried out on 110 patients with VL, 102 healthy individuals with negative leishmanin skin test (negative control group (NCG)), and 144 healthy individuals with positive leishmanin skin test (LSTPG). Four SNPs in IL-22 including rs2227501, rs2227503, rs2227513 and rs1026786 were analyzed by polymerase chain reaction-restricted fragment length polymorphism (PCR- RFLP) in the study groups. The frequency of A allele and AA genotype at rs1026786 were significantly higher in the LSTPG group than in the patients (P = 0.013 and P = 0.001, respectively). Conversely, the frequency of AG genotype was significantly higher in the patients and the NCG than in the LSTPG group (P = 0.0001 and P = 0.002, respectively). For rs2227503, the frequency of AG genotype was significantly higher in the LSTPG group than in the NCG (P = 0.025). The haplotype TGAA frequency was significantly higher in the NCG, compared to patients and LSTPG group (P = 0.004 and P = 0.023, respectively). The frequencies of haplotypes TAAG and TGAG were significantly higher in the patients than in the LSTPG group (P = 0.046 and P = 0.014, respectively). The TAAA/TAAG frequency was significantly higher in the patients than in the LSTPG group (P = 0.013). Inheritance of rs1026786 A allele and AA genotype of IL-22 could be a possible protective factor against VL, whereas the inheritance of the haplotypes TAAG and TGAG may predispose Iranian population to the disease.

The Role of Th17 Response in COVID-19

COVID-19 is an acute infectious disease of the respiratory system caused by infection with the SARS-CoV-2 virus (Severe Acute Respiratory Syndrome Coronavirus 2). Transmission of SARS-CoV-2 infections occurs through droplets and contaminated objects. A rapid and well-coordinated immune system response is the first line of defense in a viral infection. However, a disturbed and over-activated immune response may be counterproductive, causing damage to the body. Severely ill patients hospitalised with COVID-19 exhibit increased levels of many cytokines, including Interleukin (IL)-1β, IL-2, IL-6, IL-7, IL-8, IL-10, IL-17, granulocyte colony stimulating factor (G-CSF), monocyte chemoattractant protein 1 (MCP-1) and tumor necrosis factor (TNF). Increasing evidence suggests that Th17 cells play an important role in the pathogenesis of COVID-19, not only by activating cytokine cascade but also by inducing Th2 responses, inhibiting Th1 differentiation and suppressing Treg cells. This review focuses on a Th17 pathway in the course of the immune response in COVID-19, and explores plausible targets for therapeutic intervention.

Retinoic Acid: A New Old Friend of IL-17A in the Immune Pathogeny of Liver Fibrosis

Despite all the medical advances mortality due to cirrhosis and hepatocellular carcinoma, the end stages of fibrosis, continuously increases. Recent data suggest that liver fibrosis is guided by type 3 inflammation with IL-17A at the top of the line. The storage of vitamin A and its active metabolites, as well as genetics, can influence the development and progression of liver fibrosis and inflammation. Retinoic acid (active metabolite of vitamin A) is able to regulate the differentiation of IL-17A⁺/IL-22–producing cells as well as the expression of profibrotic markers. IL-17A and its pro-fibrotic role in the liver is the most studied, while the interaction and communication between IL-17A, IL-22, and vitamin A–active metabolites has not been investigated. We aim to update what is known about IL-17A, IL-22, and retinoic acid in the pathobiology of liver diseases.

A Potential Prophylactic Probiotic for Inflammatory Bowel Disease: The Overall Investigation of Clostridium tyrobutyricum ATCC25755 Attenuates LPS-Induced Inflammation via Regulating Intestinal Immune Cells

SCOPE

This study aims to roundly investigate whether Clostridium tyrobutyricum (Ct) alleviates inflammation via regulating immune cells in the small intestines.

METHODS AND RESULTS

Mice are pre-treated with different concentrations of Ct follow by LPS stimulation. Ct maintains the mice body weight under inflammation. In response to LPS, 10⁷ CFU mL^-1 Ct decreases the mRNA expression of inflammatory cytokines in the duodenum, while 10⁸ CFU mL^-1 Ct reduces inflammatory cytokines expression in both duodenum and ileum and protected intestinal morphology. The small intestinal immune cells are analyzed using flow cytometry. Ct decreases the numbers of macrophages and mast cells in the intestines in response to LPS. In the duodenum, Ct enhances dentritic cells (DCs), regulatory T cells (Tregs), and T helper cell 17 (Th17) proportions. Ct decreases DCs and Tregs proportions, while enhances Th17 numbers in the ileum. The underlying mechanism of Ct in preventing inflammation may rely on the physiological immune cell composition of the intestines. In response to LPS, Ct may mainly stimulate Tregs via activating DCs in the duodenum while trigger Th17 cells in the ileum, thereby maintaining the intestinal homeostasis.

CONCLUSION

Ct alleviates the LPS-induce inflammation via regulating different immune cell types in the small intestines, highlighting that Ct is a potential prophylactic probiotic in intestinal diseases.