Intestinal epithelia and myeloid immune cells shape colitis severity and colorectal carcinogenesis via High-mobility group box protein 1.

BACKGROUND: HMGB1 is a ubiquitous nucleoprotein with immune-regulatory properties following cellular secretion or release in sterile and infectious inflammation. Stool and serum HMGB1 levels correlate with colitis severity and colorectal cancer (CRC) progression, yet recent reports indicated HMGB1 to mainly operate as an intracellular determinant of enterocyte fate during colitis, and investigations into the roles of HMGB1 in CRC are lacking. Using mice with conditional HMGB1-knockout in enterocytes (Hmgb1ΔIEC) and myeloid cells (Hmgb1ΔLysM), respectively, we explored functions of HMGB1 in pathogenetically diverse contexts of colitis and colitis-associated CRC. RESULTS: HMGB1 is overexpressed in human inflammatory bowel disease and gastrointestinal cancers, and HMGB1 protein localizes in enterocytes and stromal cells in colitis and CRC specimens from humans and rodents. As previously described, enterocyte HMGB1 deficiency aggravates severe chemical-induced intestinal injury, but not Citrobacter rodentium or T cell transfer colitis in mice. HMGB1-deficient enterocytes and organoids do not exhibit deviant apoptotic or autophagic activity, altered proliferative or migratory capacity, abnormal intestinal permeability or aberrant DSS-induced organoid inflammation in vitro. Instead, we observed altered in vivo-reprogramming of both intestinal epithelia and infiltrating myeloid cells in Hmgb1ΔIEC early during colitis, suggesting HMGB1-mediated paracrine injury signaling. Hmgb1ΔIEC had higher CRC burden than wildtypes in the Apc+/min model, whereas inflammatory CRC was attenuated in Hmgb1ΔLysM. Cellular and molecular phenotyping of Hmgb1ΔIEC and Hmgb1ΔLysM cancers indicates context-dependent transcriptional modulation of immune signaling and extracellular matrix remodeling via HMGB1. CONCLUSION: Enterocytes and myeloid cells context-dependently regulate host responses to severe colitis and maladaptive intestinal wound healing via HMGB1.

Nmes1 is a novel regulator of mucosal response influencing intestinal healing potential.

The initiation of tissue remodeling following damage is a critical step in preventing the development of immune-mediated diseases. Several factors contribute to mucosal healing, leading to innovative therapeutic approaches for managing intestinal disorders. However, uncovering alternative targets and gaining mechanistic insights are imperative to enhance therapy efficacy and broaden its applicability across different intestinal diseases. Here we demonstrate that Nmes1, encoding for Normal Mucosa of Esophagus-Specific gene 1, also known as Aa467197, is a novel regulator of mucosal healing. Nmes1 influences the macrophage response to the tissue remodeling cytokine IL-4 in vitro. In addition, using two murine models of intestinal damage, each characterized by a type 2-dominated environment with contrasting functions, the ablation of Nmes1 results in decreased intestinal regeneration during the recovery phase of colitis, while enhancing parasitic egg clearance and reducing fibrosis during the advanced stages of Schistosoma mansoni infection. These outcomes are associated with alterations in CX3CR1+ macrophages, cells known for their wound-healing potential in the inflamed colon, hence promising candidates for cell therapies. All in all, our data indicate Nmes1 as a novel contributor to mucosal healing, setting the basis for further investigation into its potential as a new target for the treatment of colon-associated inflammation.

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.

A Gradient of Intestinal Inflammation in Primary Sclerosing Cholangitis.

BACKGROUND: Primary sclerosing cholangitis (PSC) is a progressive liver disease associated with inflammatory bowel disease (IBD). The percentage of PSC patients diagnosed with concomitant IBD varies considerably between studies. This raises the question whether all PSC patients would show intestinal inflammation if screened thoroughly, even in the absence of symptoms. METHODS: To address this question, we collected intestinal biopsies of healthy controls (n = 34), PSC (n = 25), PSC-IBD (n = 41), and IBD (n = 51) patients in a cross-sectional study and carried out cytokine expression profiling, 16S sequencing, in-depth histology, and endoscopy scoring. RESULTS: We found that the vast majority of PSC patients even without clinically manifest IBD showed infiltration of immune cells and increased expression of IL17A and IFNG in intestinal biopsies. However, expression of IL10 and FOXP3 were likewise increased, which may explain why these PSC patients have intestinal inflammation only on a molecular level. This subclinical inflammation in PSC patients was focused in the distal colon, whereas PSC-IBD patients showed inflammation either at the distal colon or on the right side of the colon and the terminal ileum. Furthermore, we observed that PSC patients without IBD showed signs of dysbiosis and exhibited a distinct microbial profile compared with healthy controls. CONCLUSIONS: We found a gradient of intestinal inflammation in the vast majority of PSC patients even in the absence of IBD. Thus, further studies evaluating the effect of anti-inflammatory therapies in PSC patients and their impact on the emergence of clinically manifest IBD and colorectal cancer development are needed.

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.

Myeloid Cell-Specific Deletion of PDGFR-α Promotes Dysbiotic Intestinal Microbiota and thus Increased Colitis Susceptibility.

BACKGROUND AND AIMS: The incidence of inflammatory bowel diseases [IBD] is steadily increasing, and thus the identification of new targets to improve therapy is a major goal. Growth factors of the PDGF family and their receptors are expressed early in intestinal development and are found in mononuclear cells and macrophages in adult tissues. Macrophages play a distinct role in the pathogenesis of IBD since their function is crucial to maintaining tolerance. METHODS: We aimed to study the role of myeloid expression of PDGFR-α in mediating intestinal homeostasis in mouse IBD and infectious models. RESULTS: Our results show that loss of myeloid PDGFR-α increases susceptibility to dextran saline sulphate-induced colitis. Accordingly, LysM-PDGFR-α-/- mice showed higher colitis scores, and reduced levels of anti-inflammatory macrophages compared to control mice. This effect was mediated via a pro-colitogenic microbiota, which developed in the absence of myeloid PDGFR-α and caused increased colitis susceptibility in gnotobiotic mice upon faecal microbiota transplantation compared to controls. Furthermore, LysM-PDGFR-α-/- mice had a leaky gut, accompanied by impaired phagocytosis, resulting in a severe barrier defect. CONCLUSIONS: Taken together, our results indicate a protective role for myeloid PDGFR-α in maintaining gut homeostasis by promoting a protective intestinal microbiota and providing an anti-inflammatory macrophage phenotype.

Microbiota-derived 3-IAA influences chemotherapy efficacy in pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDAC) is expected to be the second most deadly cancer by 2040, owing to the high incidence of metastatic disease and limited responses to treatment1,2. Less than half of all patients respond to the primary treatment for PDAC, chemotherapy3,4, and genetic alterations alone cannot explain this5. Diet is an environmental factor that can influence the response to therapies, but its role in PDAC is unclear. Here, using shotgun metagenomic sequencing and metabolomic screening, we show that the microbiota-derived tryptophan metabolite indole-3-acetic acid (3-IAA) is enriched in patients who respond to treatment. Faecal microbiota transplantation, short-term dietary manipulation of tryptophan and oral 3-IAA administration increase the efficacy of chemotherapy in humanized gnotobiotic mouse models of PDAC. Using a combination of loss- and gain-of-function experiments, we show that the efficacy of 3-IAA and chemotherapy is licensed by neutrophil-derived myeloperoxidase. Myeloperoxidase oxidizes 3-IAA, which in combination with chemotherapy induces a downregulation of the reactive oxygen species (ROS)-degrading enzymes glutathione peroxidase 3 and glutathione peroxidase 7. All of this results in the accumulation of ROS and the downregulation of autophagy in cancer cells, which compromises their metabolic fitness and, ultimately, their proliferation. In humans, we observed a significant correlation between the levels of 3-IAA and the efficacy of therapy in two independent PDAC cohorts. In summary, we identify a microbiota-derived metabolite that has clinical implications in the treatment of PDAC, and provide a motivation for considering nutritional interventions during the treatment of patients with cancer.

Macrophages and glia are the dominant P2X7-expressing cell types in the gut nervous system-No evidence for the role of neuronal P2X7 receptors in colitis.

The blockade or deletion of the pro-inflammatory P2X7 receptor channel has been shown to reduce tissue damage and symptoms in models of inflammatory bowel disease, and P2X7 receptors on enteric neurons were suggested to mediate neuronal death and associated motility changes. Here, we used P2X7-specific antibodies and nanobodies, as well as a bacterial artificial chromosome transgenic P2X7-EGFP reporter mouse model and P2rx7-/- controls to perform a detailed analysis of cell type-specific P2X7 expression and possible overexpression effects in the enteric nervous system of the distal colon. In contrast to previous studies, we did not detect P2X7 in neurons but found dominant expression in glia and macrophages, which closely interact with the neurons. The overexpression of P2X7 per se did not induce significant pathological effects. Our data indicate that macrophages and/or glia account for P2X7-mediated neuronal damage in inflammatory bowel disease and provide a refined basis for the exploration of P2X7-based therapeutic strategies.

Tissue resident iNKT17 cells facilitate cancer cell extravasation in liver metastasis via interleukin-22.

During metastasis, cancer cells invade, intravasate, enter the circulation, extravasate, and colonize target organs. Here, we examined the role of interleukin (IL)-22 in metastasis. Immune cell-derived IL-22 acts on epithelial tissues, promoting regeneration and healing upon tissue damage, but it is also associated with malignancy. Il22-deficient mice and mice treated with an IL-22 antibody were protected from colon-cancer-derived liver and lung metastasis formation, while overexpression of IL-22 promoted metastasis. Mechanistically, IL-22 acted on endothelial cells, promoting endothelial permeability and cancer cell transmigration via induction of endothelial aminopeptidase N. Multi-parameter flow cytometry and single-cell sequencing of immune cells isolated during cancer cell extravasation into the liver revealed iNKT17 cells as source of IL-22. iNKT-cell-deficient mice exhibited reduced metastases, which was reversed by injection of wild type, but not Il22-deficient, invariant natural killer T (iNKT) cells. IL-22-producing iNKT cells promoting metastasis were tissue resident, as demonstrated by parabiosis. Thus, IL-22 may present a therapeutic target for prevention of metastasis.

Tissue Sampling and Homogenization with NIRL Enables Spatially Resolved Cell Layer Specific Proteomic Analysis of the Murine Intestine.

For investigating the molecular physiology and pathophysiology in organs, the most exact data should be obtained; if not, organ-specific cell lines are analyzed, or the whole organ is homogenized, followed by the analysis of its biomolecules. However, if the morphological organization of the organ can be addressed, then, in the best case, the composition of molecules in single cells of the target organ can be analyzed. Laser capture microdissection (LCM) is a technique which enables the selection of specific cells of a tissue for further analysis of their molecules. However, LCM is a time-consuming two-dimensional technique, and optimal results are only obtained if the tissue is fixed, e.g., by formalin. Especially for proteome analysis, formalin fixation reduced the number of identifiable proteins, and this is an additional drawback. Recently, it was demonstrated that sampling of fresh-frozen (non-fixed) tissue with an infrared-laser is giving higher yields with respect to the absolute protein amount and number of identifiable proteins than conventional mechanical homogenization of tissues. In this study, the applicability of the infrared laser tissue sampling for the proteome analysis of different cell layers of murine intestine was investigated, using LC-MS/MS-based differential quantitative bottom-up proteomics. By laser ablation, eight consecutive layers of colon tissue were obtained and analyzed. However, a clear distinguishability of protein profiles between ascending, descending, and transversal colon was made, and we identified the different intestinal-cell-layer proteins, which are cell-specific, as confirmed by data from the Human Protein Atlas. Thus, for the first time, sampling directly from intact fresh-frozen tissue with three-dimensional resolution is giving access to the different proteomes of different cell layers of colon tissue.

Characterization of serum biomarkers and antibody responses against Prevotella spp. in preclinical and new-onset phase of rheumatic diseases.

Introduction: The characterization of the influence of the microbiota on the development and drug responses during rheumatic diseases has intensified in recent years. The role of specific bacteria during disease development has become a central research question. Notably, several lines of evidence point to distinct microbes, e.g., Prevotella copri (P. copri) being targeted by antibodies in clinical phases of rheumatic diseases. Methods: In the present study, we compiled a broad collection of human serum samples from individuals at risk of developing RA, chronic RA patients as well as patients with new-onset of rheumatic diseases. We evaluated the presence of inflammatory biomarkers in our serum collection as well as serum antibody responses against novel, genetically distinct isolates of P. copri and several oral pathobionts. Results: Our analysis revealed the presence of increased levels of inflammatory markers already in pre-clinical and new onset rheumatoid arthritis. However, antibody reactivity against the microbes did not differ between patient groups. Yet, we observed high variability between the different P. copri strains. We found total serum IgG levels to slightly correlate with IgG antibody responses against P. copri, but no relation between the latter and presence or prevalence of P. copri in the intestine. Discussion: In conclusion, our work underlined the importance of strain-level characterization and its consideration during further investigations of host-microbiota interactions and the development of microbiome-based therapeutic approaches for treating rheumatic diseases.

Tissue Sampling and Homogenization in the Sub-Microliter Scale with a Nanosecond Infrared Laser (NIRL) for Mass Spectrometric Proteomics.

It was recently shown that ultrashort pulse infrared (IR) lasers, operating at the wavelength of the OH vibration stretching band of water, are highly efficient for sampling and homogenizing biological tissue. In this study we utilized a tunable nanosecond infrared laser (NIRL) for tissue sampling and homogenization with subsequent liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis for mass spectrometric proteomics. For the first time, laser sampling was performed with murine spleen and colon tissue. An ablation volume of 1.1 × 1.1 × 0.4 mm³ (approximately 0.5 µL) was determined with optical coherence tomography (OCT). The results of bottom-up proteomics revealed proteins with significant abundance differences for both tissue types, which are in accordance with the corresponding data of the Human Protein Atlas. The results demonstrate that tissue sampling and homogenization of small tissue volumes less than 1 µL for subsequent mass spectrometric proteomics is feasible with a NIRL.

Microbiota-Dependent Effects of IL-22.

Cytokines are important contributors to immune responses against microbial and environmental threats and are of particular importance at epithelial barriers. These interfaces are continuously exposed to external factors and thus require immune components to both protect the host from pathogen invasion and to regulate overt inflammation. Recently, substantial efforts have been devoted to understanding how cytokines act on certain cells at barrier sites, and why the dysregulation of immune responses may lead to pathogenesis. In particular, the cytokine IL-22 is involved in preserving an intact epithelium, maintaining a balanced microbiota and a functioning defense system against external threats. However, a tight regulation of IL-22 is generally needed, since uncontrolled IL-22 production can lead to the progression of autoimmunity and cancer. Our aim in this review is to summarize novel findings on IL-22 and its interactions with specific microbial stimuli, and subsequently, to understand their contributions to the function of IL-22 and the clinical outcome. We particularly focus on understanding the detrimental effects of dysregulated control of IL-22 in certain disease contexts.

IL22BP Mediates the Antitumor Effects of Lymphotoxin Against Colorectal Tumors in Mice and Humans.

BACKGROUND & AIMS: Unregulated activity of interleukin (IL) 22 promotes intestinal tumorigenesis in mice. IL22 binds the antagonist IL22 subunit alpha 2 (IL22RA2, also called IL22BP). We studied whether alterations in IL22BP contribute to colorectal carcinogenesis in humans and mice. METHODS: We obtained tumor and nontumor tissues from patients with colorectal cancer (CRC) and measured levels of cytokines by quantitative polymerase chain reaction, flow cytometry, and immunohistochemistry. We measured levels of Il22bp messenger RNA in colon tissues from wild-type, Tnf-/-, Lta-/-, and Ltb-/- mice. Mice were given azoxymethane and dextran sodium sulfate to induce colitis and associated cancer or intracecal injections of MC38 tumor cells. Some mice were given inhibitors of lymphotoxin beta receptor (LTBR). Intestine tissues were analyzed by single-cell sequencing to identify cell sources of lymphotoxin. We performed immunohistochemistry analysis of colon tissue microarrays from patients with CRC (1475 tissue cores, contained tumor and nontumor tissues) and correlated levels of IL22BP with patient survival times. RESULTS: Levels of IL22BP were decreased in human colorectal tumors, compared with nontumor tissues, and correlated with levels of lymphotoxin. LTBR signaling was required for expression of IL22BP in colon tissues of mice. Wild-type mice given LTBR inhibitors had an increased tumor burden in both models, but LTBR inhibitors did not increase tumor growth in Il22bp-/- mice. Lymphotoxin directly induced expression of IL22BP in cultured human monocyte-derived dendritic cells via activation of nuclear factor κB. Reduced levels of IL22BP in colorectal tumor tissues were associated with shorter survival times of patients with CRC. CONCLUSIONS: Lymphotoxin signaling regulates expression of IL22BP in colon; levels of IL22BP are reduced in human colorectal tumors, associated with shorter survival times. LTBR signaling regulates expression of IL22BP in colon tumors in mice and cultured human dendritic cells. Patients with colorectal tumors that express low levels of IL22BP might benefit from treatment with an IL22 antagonist.

Systemic interleukin 10 levels indicate advanced stages while interleukin 17A levels correlate with reduced survival in esophageal adenocarcinomas.

INTRODUCTION: Reflux promotes esophageal adenocarcinomas (EAC) creating a chronic inflammatory environment. EAC show an increasing incidence in the Western World and median survival rates are still low. The main reasons for poor prognosis despite new multimodal therapies are diagnosis of EACs at an already advanced stage and distant metastases. Hence, we wanted to investigate the presence of systemic inflammatory interleukins (IL) and their impact on patient prognosis. MATERIAL AND METHODS: Systemic expression levels of pro- and anti-inflammatory markers (IL-2, IL-4, IL-6, IL-10, IL-17A and IL-22) in the sera of 43 EAC patients without neoadjuvant radiochemotherapy were measured by flow cytometric analysis. A correlation to clinicopathological data was performed. Log-rank and Cox regression analysis were used to investigate the impact on patient survival. 43 sera of age and gender matched healthy volunteers were used as controls. RESULTS: Increased systemic IL-6 (p = 0.044) and lower IL-17A (p = 0.002) levels were found in EAC patients as opposed to controls. A correlation of IL-10 levels with an increased T stage was found (p = 0.020). Also, systemic IL-10 levels were highly elevated in patients with distant metastasis (p<0.001). However, only systemic IL-17A levels had an influence on patient survival in multivariate analysis. CONCLUSION: Systemic IL-6 levels are increased, while IL-17A levels are reduced in EAC patients compared to healthy controls. In addition, circulating IL-10 might help to identify patients with advanced disease and high IL-17A might indicate a limited prognosis.

Anti-inflammatory microenvironment of esophageal adenocarcinomas negatively impacts survival.

OBJECTIVE: Reflux promotes esophageal adenocarcinomas (EACs) creating a chronic inflammatory environment. Survival rates are low due to early local recurrences and distant metastasis. Hence, there is a need for new potential treatment options like immunotherapies. However, the inflammatory microenvironment in EACs and its impact on patient outcome remain to be fully understood. METHODS: mRNA expression levels of pro- and anti-inflammatory markers in 39 EAC patients without neoadjuvant radio-chemotherapy were measured. Data were confirmed using flow cytometric analysis of freshly resected surgical specimens. Inflammatory alterations in premalignant lesions of Barrett's esophagus were analyzed by immunohistochemistry. RESULTS: Expression levels of IL22 were reduced in EAC, while expression levels of FOXP3, IL10 and CTLA4 were increased. Flow cytometry demonstrated a strong infiltration of CD4+ T cells with a reduction in CD4+ T cells producing IL-22 or IL-17A. We also observed an increase in CD4+CD127lowFOXP3+ cells producing IL-10. Accumulation of FOXP3+ T cells occurred prior to malignant changes. High expression of IL10 and low expression of IL22 in EAC were associated with reduced overall survival. Moreover, increased expression of IL10, CTLA4 and PD1 in the unaltered esophageal mucosa distant to the EAC was also linked with an unfavorable prognosis. CONCLUSION: EAC shows an anti-inflammatory environment, which strongly affects patient survival. The microscopically unaltered peritumoral tissue shows a similar anti-inflammatory pattern indicating an immunological field effect, which might contribute to early local recurrences despite radical resection. These data suggest that using checkpoint inhibitors targeting anti-inflammatory T cells would be a promising therapeutic strategy in EAC.

Regulation of IL-22BP in psoriasis.

IL-22 is a potent pro-inflammatory cytokine upregulated in psoriasis and in other inflammatory diseases. The function of IL-22 is regulated by the soluble scavenging receptor, IL-22 binding protein (IL-22BP or IL-22RA2). However, the role and regulation of IL-22BP itself in the pathogenesis of inflammatory disease remain unclear. We used the TLR7 agonist Imiquimod (IMQ) to induce a psoriasis-like skin disease in mice and found a strong downregulation of IL-22BP in the affected skin as well as in the lymph nodes of animals treated with IMQ. We also analysed psoriatic skin of patients and compared this to skin of healthy donors. Interestingly, IL-22BP expression was similarly downregulated in skin biopsies of psoriasis patients compared to the skin of healthy donors. Since IL-22BP is expressed foremost in dendritic cells, we characterized its expression in monocyte-derived dendritic cells (MoDC) during maturation. In this way, we found Prostaglandin E2 (PGE2) to be a potent suppressor of IL-22BP expression in vitro. We conclude that regulation of IL-22BP by inflammatory mediators is an important step for the progression of inflammation in the skin and possibly also in other autoimmune diseases.

IL-10 Receptor Signaling Is Essential for TR1 Cell Function In Vivo.

IL-10 is essential to maintain intestinal homeostasis. CD4+ T regulatory type 1 (TR1) cells produce large amounts of this cytokine and are therefore currently being examined in clinical trials as T cell therapy in patients with inflammatory bowel disease. However, factors and molecular signals sustaining TR1 cell regulatory activity still need to be identified to optimize the efficiency and ensure the safety of these trials. We investigated the role of IL-10 signaling in mature TR1 cells in vivo. Double IL-10eGFP Foxp3mRFP reporter mice and transgenic mice with impairment in IL-10 receptor signaling were used to test the activity of TR1 cells in a murine inflammatory bowel disease model, a model that resembles the trials performed in humans. The molecular signaling was elucidated in vitro. Finally, we used human TR1 cells, currently employed for cell therapy, to confirm our results. We found that murine TR1 cells expressed functional IL-10Rα. TR1 cells with impaired IL-10 receptor signaling lost their regulatory activity in vivo. TR1 cells required IL-10 receptor signaling to activate p38 MAPK, thereby sustaining IL-10 production, which ultimately mediated their suppressive activity. Finally, we confirmed these data using human TR1 cells. In conclusion, TR1 cell regulatory activity is dependent on IL-10 receptor signaling. These data suggest that to optimize TR1 cell-based therapy, IL-10 receptor expression has to be taken into consideration.

A pathogenic role for T cell-derived IL-22BP in inflammatory bowel disease.

Intestinal inflammation can impair mucosal healing, thereby establishing a vicious cycle leading to chronic inflammatory bowel disease (IBD). However, the signaling networks driving chronic inflammation remain unclear. Here we report that CD4+ T cells isolated from patients with IBD produce high levels of interleukin-22 binding protein (IL-22BP), the endogenous inhibitor of the tissue-protective cytokine IL-22. Using mouse models, we demonstrate that IBD development requires T cell-derived IL-22BP. Lastly, intestinal CD4+ T cells isolated from IBD patients responsive to treatment with antibodies against tumor necrosis factor-α (anti-TNF-α), the most effective known IBD therapy, exhibited reduced amounts of IL-22BP expression but still expressed IL-22. Our findings suggest that anti-TNF-α therapy may act at least in part by suppressing IL-22BP and point toward a more specific potential therapy for IBD.

IL-23 prevents IL-13-dependent tissue repair associated with Ly6C(lo) monocytes in Entamoeba histolytica-induced liver damage.

BACKGROUND & AIMS: The IL-23/IL-17 axis plays an important role in the pathogenesis of autoimmune diseases and the pathological consequences of infection. We previously showed that immunopathologic mechanisms mediated by inflammatory monocytes underlie the severe focal liver damage induced by the protozoan parasite, Entamoeba histolytica. Here, we analyze the contribution of the IL-23/IL-17 axis to the induction and subsequent recovery from parasite-induced liver damage. METHODS: IL-23p19(-/-), IL-17A/F(-/-), CCR2(-/-), and wild-type (WT) mice were intra-hepatically infected with E. histolytica trophozoites and disease onset and recovery were analyzed by magnetic resonance imaging. Liver-specific gene and protein expression during infection was examined by qPCR, microarray, FACS analysis and immunohistochemistry. Immuno-depletion and substitution experiments were performed in IL-23p19(-/-) and WT mice to investigate the role of IL-13 in disease outcome. RESULTS: Liver damage in infected IL-23p19(-/-), IL-17A/F(-/-), and CCR2(-/-) mice was strongly attenuated compared with that in WT mice. IL-23p19(-/-) mice showed reduced accumulation of IL-17 and CCL2 mRNA and proteins. Increased numbers of IL-13-producing CD11b(+)Ly6C(lo) monocytes were associated with disease attenuation in IL-23p19(-/-) mice. Immuno-depletion of IL-13 in IL-23p19(-/-) mice reversed this attenuation and treatment of infected WT mice with an IL-13/anti-IL-13-mAb complex supported liver recovery. CONCLUSIONS: The IL-23/IL-17 axis plays a critical role in the immunopathology of hepatic amebiasis. IL-13 secreted by CD11b(+)Ly6C(lo) monocytes may be associated with recovery from liver damage. An IL-13/anti-IL13-mAb complex mimics this function, suggesting a novel therapeutic option to support tissue healing after liver damage.