Microbiota Sensing by Mincle-Syk Axis in Dendritic Cells Regulates Interleukin-17 and -22 Production and Promotes Intestinal Barrier Integrity.

Production of interleukin-17 (IL-17) and IL-22 by T helper 17 (Th17) cells and group 3 innate lymphoid cells (ILC3s) in response to the gut microbiota ensures maintenance of intestinal barrier function. Here, we examined the mechanisms whereby the immune system detects microbiota in the steady state. A Syk-kinase-coupled signaling pathway in dendritic cells (DCs) was critical for commensal-dependent production of IL-17 and IL-22 by CD4+ T cells. The Syk-coupled C-type lectin receptor Mincle detected mucosal-resident commensals in the Peyer's patches (PPs), triggered IL-6 and IL-23p19 expression, and thereby regulated function of intestinal Th17- and IL-17-secreting ILCs. Mice deficient in Mincle or with selective depletion of Syk in CD11c+ cells had impaired production of intestinal RegIIIγ and IgA and increased systemic translocation of gut microbiota. Consequently, Mincle deficiency led to liver inflammation and deregulated lipid metabolism. Thus, sensing of commensals by Mincle and Syk signaling in CD11c+ cells reinforces intestinal immune barrier and promotes host-microbiota mutualism, preventing systemic inflammation.

miRNome profiling of extracellular vesicles in severe COVID-19 patients and identification of predictors of mortality.

BACKGROUND: Extracellular vesicles (EVs), containing microRNAs (miRNAs) and other molecules, play a central role in intercellular communication, especially in viral infections caused by SARS-CoV-2. This study explores the miRNA profiles in plasma-derived EVs from severe COVID-19 patients referred to controls, identifying potential mortality miRNA predictors. METHODS: A prospective study was carried out, including 36 severe COVID-19 patients and 33 non-COVID-19 controls. EVs-derived miRNAs were sequenced, and bioinformatics and differential expression analysis between groups were performed. The plasma miRNA profile of an additional cohort of severe COVID-19 patients (n=32) and non-COVID-19 controls (n=12) was used to compare with our data. Survival analysis was used to identify potential mortality predictors among the SDE miRNAs in EVs. RESULTS: Severe COVID-19 patients showed 50 significantly differentially expressed (SDE) miRNAs in plasma-derived EVs. These miRNAs were associated with pathways related to inflammation and cell adhesion. Fifteen of these plasma-derived EVs miRNAs were also SDE in the plasma of severe patients vs controls. Two miRNAs, hsa-miR-1469 and hsa-miR-6124, were identified as strong mortality predictors with an área under the ROC Curve (AUC) of 0.938. CONCLUSION: : This research provides insights into the role of miRNAs found within EVs in severe COVID-19 and their potential as clinical biomarkers for mortality.

Genetic Architecture of Ischaemic Strokes after COVID-19 Shows Similarities with Large Vessel Strokes.

We aimed to analyse whether patients with ischaemic stroke (IS) occurring within eight days after the onset of COVID-19 (IS-COV) are associated with a specific aetiology of IS. We used SUPERGNOVA to identify genome regions that correlate between the IS-COV cohort (73 IS-COV cases vs. 701 population controls) and different aetiological subtypes. Polygenic risk scores (PRSs) for each subtype were generated and tested in the IS-COV cohort using PRSice-2 and PLINK to find genetic associations. Both analyses used the IS-COV cohort and GWAS from MEGASTROKE (67,162 stroke patients vs. 454,450 population controls), GIGASTROKE (110,182 vs. 1,503,898), and the NINDS Stroke Genetics Network (16,851 vs. 32,473). Three genomic regions were associated (p-value < 0.05) with large artery atherosclerosis (LAA) and cardioembolic stroke (CES). We found four loci targeting the genes PITX2 (rs10033464, IS-COV beta = 0.04, p-value = 2.3 × 10-2, se = 0.02), previously associated with CES, HS6ST1 (rs4662630, IS-COV beta = -0.04, p-value = 1.3 × 10-3, se = 0.01), TMEM132E (rs12941838 IS-COV beta = 0.05, p-value = 3.6 × 10-4, se = 0.01), and RFFL (rs797989 IS-COV beta = 0.03, p-value = 1.0 × 10-2, se = 0.01). A statistically significant PRS was observed for LAA. Our results suggest that IS-COV cases are genetically similar to LAA and CES subtypes. Larger cohorts are needed to assess if the genetic factors in IS-COV cases are shared with the general population or specific to viral infection.

Plasma levels of intestinal fatty-acid binding protein (I-FABP), abdominal distension and hydrogen concentration after lactitol small intestinal bacterial overgrowth (SIBO) test.

Breath tests with glucose, lactulose or lactitol are useful for diagnosis of small intestinal bacterial overgrowth (SIBO). Nevertheless, they have suboptimal sensitivity and specificity and, indeed, are positive in a considerable number of patients with irritable bowel syndrome (IBS). The complexity in the management of patients with functional intestinal disorders and the availability of these tests are leading to frequent diagnoses of SIBO. Intestinal Fatty-Acid Binding protein (I-FABP) is a protein present in the cytosol of intestinal epithelial cells. Its plasmatic levels have been related to different enteropathies and, therefore, could be a marker of early intestinal damage with unconfirmed clinical utility. Hence, we have studied the plasmatic I-FABP level of patients who are requested a lactitol test to confirm SIBO and related it to clinical and laboratory characteristics and SIBO test results.

Guidelines for the use of flow cytometry and cell sorting in immunological studies (third edition).

The third edition of Flow Cytometry Guidelines provides the key aspects to consider when performing flow cytometry experiments and includes comprehensive sections describing phenotypes and functional assays of all major human and murine immune cell subsets. Notably, the Guidelines contain helpful tables highlighting phenotypes and key differences between human and murine cells. Another useful feature of this edition is the flow cytometry analysis of clinical samples with examples of flow cytometry applications in the context of autoimmune diseases, cancers as well as acute and chronic infectious diseases. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid. All sections are written and peer-reviewed by leading flow cytometry experts and immunologists, making this edition an essential and state-of-the-art handbook for basic and clinical researchers.

Altered Surface Expression of Insulin-Degrading Enzyme on Monocytes and Lymphocytes from COVID-19 Patients Both at Diagnosis and after Hospital Discharge.

Although the COVID-19 disease has developed into a worldwide pandemic, its pathophysiology remains to be fully understood. Insulin-degrading enzyme (IDE), a zinc-metalloprotease with a high affinity for insulin, has been found in the interactomes of multiple SARS-CoV-2 proteins. However, the relevance of IDE in the innate and adaptative immune responses elicited by circulating peripheral blood mononuclear cells is unknown. Here, we show that IDE is highly expressed on the surface of circulating monocytes, T-cells (both CD4+ and CD4-), and, to a lower extent, in B-cells from healthy controls. Notably, IDE's surface expression was upregulated on monocytes from COVID-19 patients at diagnosis, and it was increased in more severe patients. However, IDE's surface expression was downregulated (relative to healthy controls) 3 months after hospital discharge in all the studied immune subsets, with this effect being more pronounced in males than in females, and thus it was sex-dependent. Additionally, IDE levels in monocytes, CD4+ T-cells, and CD4- T-cells were inversely correlated with circulating insulin levels in COVID-19 patients (both at diagnosis and after hospital discharge). Of note, high glucose and insulin levels downregulated IDE surface expression by ~30% in the monocytes isolated from healthy donors, without affecting its expression in CD4+ T-cells and CD4- T-cells. In conclusion, our studies reveal the sex- and metabolism-dependent regulation of IDE in monocytes, suggesting that its regulation might be important for the recruitment of immune cells to the site of infection, as well as for glucometabolic control, in COVID-19 patients.

Is celiac disease really associated with inflammatory bowel disease?

Celiac disease (CeD) and inflammatory bowel disease (IBD) are chronic gastrointestinal disorders of inflammatory origin that develop in response to environmental triggers in genetically predisposed individuals. CeD localizes in the duodenal mucosa, where intolerance develops to dietary gluten from wheat, barley, rye, and some varieties of oats. IBD, in turn, is subdivided primarily into Crohn's disease (CD) and colitis, with ulcerative colitis (UC) being the most thoroughly investigated form.

Duodenal lymphogram as a complementary tool in the diagnosis of celiac disease in adults.

INTRODUCTION: celiac disease (CD) patients have a specific pattern of lymphocytic infiltrate in the duodenal mucosa. Flow cytometry is a complementary tool for the diagnosis of CD, which allows the quantification and characterization of intraepithelial lymphocytes (IELs) by what is commonly called a lymphogram. Here we describe our experience with this technique in the diagnosis of CD in adult patients. METHODS: lymphograms from 157 patients performed in our center between 2009 and 2017 were retrospectively analyzed. Fourteen patients had a previous diagnosis of CD and followed a gluten-free diet (GFD), 21 had a new diagnosis of CD and the remaining were considered as non-celiac. The association of the lymphogram results (total IELs, CD3- lymphocytes and TcRγδ lymphocytes) with the CD diagnosis, compliance with the GFD, time since diagnosis and IgA anti-TG2 titer were determined. RESULTS: the area under the ROC curve of TcRγδ lymphocytes for CD patients varied between 0.86 and 0.86. The percentage of TcRγδ lymphocytes in GFD-treated patients was lower; 12 (8.5) vs 20.5 (8.7), p = 0.0153. However, it remained high compared to non-CD; 12 (8.5) vs 6.7 (6), p = 0.135. The time since diagnosis and IgA anti-TG2 titer correlated with the lymphogram results. Helicobacter pylori infection and treatment with angiotensin receptor antagonist 2 (ARA2) were associated with differences in the lymphogram results in patients without CD. CONCLUSIONS: the duodenal lymphogram is a reliable complementary tool in adults for the diagnosis of CD. However, compliance and duration of the GFD and other factors may condition its diagnostic capacity.

Correlation Between Anti-TNF Serum Levels and Endoscopic Inflammation in Inflammatory Bowel Disease Patients.

OBJECTIVES: (a) To evaluate the diagnostic accuracy of anti-TNF trough levels to predict mucosal healing in inflammatory bowel disease (IBD); (b) to determine the best cut-off point to predict mucosal healing in IBD patients treated with anti-TNF. METHODS: This is a multicenter, prospective study. IBD patients under anti-TNF treatment for at least 6 months that had to undergo an endoscopy were included. Mucosal healing was defined as: Simple endoscopic score for Crohn's Disease < 3 for Crohn's disease (CD), Rutgeerts score < i2 for CD in postoperative setting, or Mayo endoscopic score ≤ 1 for ulcerative colitis (UC). Anti-TNF concentrations were measured using SMART ELISAs at trough. RESULTS: A total of 182 patients were included. Anti-TNF trough levels were significantly higher among patients that had mucosal healing than among those who did not. The area under the curve of infliximab for mucosal healing was 0.63 (best cutoff value 3.4 µg/mL), and for adalimumab 0.60 (best cutoff value 7.2 µg/mL). In the multivariate analysis, having anti-TNF drug levels above the cutoff values [odds ratio (OR) 3.1]) and having UC instead of CD (OR 4) were associated with a higher probability of having mucosal healing. Additionally, the need for an escalated dosage (OR 0.2) and current smoking habit (OR 0.2) were also associated with a lower probability of mucosal healing. CONCLUSIONS: There was an association between anti-TNF trough levels and mucosal healing in IBD patients; however, the accuracy of the determination of infliximab and adalimumab concentrations able to predict mucosal healing was suboptimal.

Compartment-specific immunity in the human gut: properties and functions of dendritic cells in the colon versus the ileum.

OBJECTIVE: Dendritic cells (DC) mediate intestinal immune tolerance. Despite striking differences between the colon and the ileum both in function and bacterial load, few studies distinguish between properties of immune cells in these compartments. Furthermore, information of gut DC in humans is scarce. We aimed to characterise human colonic versus ileal DC. DESIGN: Human DC from paired colonic and ileal samples were characterised by flow cytometry, electron microscopy or used to stimulate T cell responses in a mixed leucocyte reaction. RESULTS: A lower proportion of colonic DC produced pro-inflammatory cytokines (tumour necrosis factor-α and interleukin (IL)-1ß) compared with their ileal counterparts and exhibited an enhanced ability to generate CD4(+)FoxP3(+)IL-10(+) (regulatory) T cells. There were enhanced proportions of CD103(+)Sirpα(-) DC in the colon, with increased proportions of CD103(+)Sirpα(+) DC in the ileum. A greater proportion of colonic DC subsets analysed expressed the lymph-node-homing marker CCR7, alongside enhanced endocytic capacity, which was most striking in CD103(+)Sirpα(+) DC. Expression of the inhibitory receptor ILT3 was enhanced on colonic DC. Interestingly, endocytic capacity was associated with CD103(+) DC, in particular CD103(+)Sirpα(+) DC. However, expression of ILT3 was associated with CD103(-) DC. Colonic and ileal DC differentially expressed skin-homing marker CCR4 and small-bowel-homing marker CCR9, respectively, and this corresponded to their ability to imprint these homing markers on T cells. CONCLUSIONS: The regulatory properties of colonic DC may represent an evolutionary adaptation to the greater bacterial load in the colon. The colon and the ileum should be regarded as separate entities, each comprising DC with distinct roles in mucosal immunity and imprinting.

Body composition of the host influences dendritic cell phenotype in patients treated for colorectal cancer.

Dendritic cells (DCs) are antigen-presenting cells that can acquire tumour antigens and initiate cytotoxic T cell reactions. Obesity has been proposed as a cause for tumours escaping immune surveillance, but few studies investigate the impact of other body composition parameters. We examined the relationship of DC phenotype with computer tomography (CT)-defined parameters in patients with colorectal cancer (CRC). DCs were identified within peripheral blood mononuclear cells by flow cytometry as HLA-DR positive and negative for markers of other cell lineages in 21 patients. Analysis of CT scans was used to calculate lumbar skeletal muscle index (LSMI) and mean muscle attenuation (MA). Positive correlation between the LSMI and expression of CD40 in all DCs (r = 0.45; p = 0.04) was demonstrated. The MA was positively correlated with scavenger receptor CD36 [all DCs (r = 0.60; p = 0.01) and myeloid DCs (r = 0.63; p < 0.01)]. However, the MA was negatively correlated with CCR7 expression in all DCs (r = -0.46, p = 0.03.) and with CD83 [all DCs (r = -0.63; p = 0.01) and myeloid DCs (r = -0.75; p < 0.01)]. There were no relationships between the fat indexes and the DC phenotype. These results highlight a direct relationship between muscle depletion and changes in stimulatory, migratory and fatty acid-processing potential of DC in patients with CRC.

Immunogenetic Pathogenesis of Celiac Disease and Non-celiac Gluten Sensitivity.

Celiac disease is the most common oral intolerance in Western countries. It results from an immune response towards gluten proteins from certain cereals in genetically predisposed individuals (HLA-DQ2 and/or HLA-DQ8). Its pathogenesis involves the adaptive (HLA molecules, transglutaminase 2, dendritic cells, and CD4(+) T-cells) and the innate immunity with an IL-15-mediated response elicited in the intraepithelial compartment. At present, the only treatment is a permanent strict gluten-free diet (GFD). Multidisciplinary studies have provided a deeper insight of the genetic and immunological factors and their interaction with the microbiota in the pathogenesis of the disease. Similarly, a better understanding of the composition of the toxic gluten peptides has improved the ways to detect them in food and drinks and how to monitor GFD compliance via non-invasive approaches. This review, therefore, addresses the major findings obtained in the last few years including the re-discovery of non-celiac gluten sensitivity.

The prognostic significance and relationship with body composition of CCR7-positive cells in colorectal cancer.

BACKGROUND AND OBJECTIVES: The host local immune response (LIR) to cancer is a determinant of cancer outcome. Regulation of this local response is largely achieved through chemokine synthesis from the tumor microenvironment such as C-Chemokine-Receptor-7 (CCR7). We examined the LIR measured as CCR7 expression, in colorectal cancers (CRC) and explored relationships with body composition (BC) and survival. METHODS: A study of paraffin-embedded tissue specimens was carried out in 116 patients with non-metastatic CRC. CCR7 expression was determined by immunohistochemistry. Analysis of computer tomography scans was used to calculate BC parameters. Survival analyses and multivariate regression models were used. RESULTS: High CCR7(+) cell density within the tumor stroma and at the margin was significantly associated with increased age, the presence of lymphovascular invasion, higher tumor stage, lymph node metastasis, high Klintrup-Makinen immune score, and myosteatosis. High CCR7(+) cell density in the tumor margin was significantly associated with shorter disease-free (DFS) and overall survival (OS) (P < 0.001). This was also significantly associated with shorter survival in multivariate analysis (HR = 8.87; 95%CI [2.51-31.3]; P < 0.01 for OS and HR = 4.72; 95%CI (1.24-12.9); P = 0.02 for DFS). CONCLUSIONS: Our results suggest that a specific immune microenvironment may be associated with altered host's BC and tumor behavior, and that CCR7 may serve as a novel prognostic biomarker.

Innate lymphoid cells and natural killer T cells in the gastrointestinal tract immune system.

The gastrointestinal tract is equipped with a highly specialized intrinsic immune system. However, the intestine is exposed to a high antigenic burden that requires a fast, nonspecific response -so-called innate immunity- to maintain homeostasis and protect the body from incoming pathogens. In the last decade multiple studies helped to unravel the particular developmental requirements and specific functions of the cells that play a role in innate immunity. In this review we shall focus on innate lymphoid cells, a newly discovered, heterogeneous set of cells that derive from an Id2-dependent lymphoid progenitor cell population. These cells have been categorized on the basis of the pattern of cytokines that they secrete, and the transcription factors that regulate their development and functions. Innate lymphoid cells play a role in the early response to pathogens, the anatomical contention of the commensal flora, and the maintenance of epithelial integrity.Amongst the various innate lymphoid cells we shall lay emphasis on a subpopulation with several peculiarities, namely that of natural killer T cells, a subset of T lymphocytes that express both T-cell and NK-cell receptors. The most numerous fraction of the NKT population are the so-called invariant NKT or iNKT cells. These iNKT cells have an invariant TCR and recognize the glycolipidic structures presented by the CD1d molecule, a homolog of class-I MHC molecules. Following activation they rapidly acquire cytotoxic activity and secrete both Th1 and Th2 cytokines, including IL-17. While their specific role is not yet established, iNKT cells take part in a great variety of intestinal immune responses ranging from oral tolerance to involvement in a number of gastrointestinal conditions.

State-of-the-art cytometry in the search of novel biomarkers in digestive cancers.

Despite that colorectal and liver cancer are among the most prevalent tumours in the world, the identification of non-invasive biomarkers to aid on their diagnose and subsequent prognosis is a current unmet need that would diminish both their incidence and mortality rates. In this context, conventional flow cytometry has been widely used in the screening of biomarkers with clinical utility in other malignant processes like leukaemia or lymphoma. Therefore, in this review, we will focus on how advanced cytometry panels covering over 40 parameters can be applied on the study of the immune system from patients with colorectal and hepatocellular carcinoma and how that can be used on the search of novel biomarkers to aid or diagnose, prognosis, and even predict clinical response to different treatments. In addition, these multiparametric and unbiased approaches can also provide novel insights into the specific immunopathogenic mechanisms governing these malignant diseases, hence potentially unravelling novel targets to perform immunotherapy or identify novel mechanisms, rendering the development of novel treatments. As a consequence, computational cytometry approaches are an emerging methodology for the early detection and predicting therapies for gastrointestinal cancers.

Circulating immunome fingerprint in eosinophilic esophagitis is associated with clinical response to proton pump inhibitor treatment.

Objectives: The aim of the study was to characterize the circulating immunome of patients with EoE before and after proton pump inhibitor (PPI) treatment in order to identify potential non-invasive biomarkers of treatment response. Methods: PBMCs from 19 healthy controls and 24 EoE patients were studied using a 39-plex spectral cytometry panel. The plasmacytoid dendritic cell (pDC) population was differentially characterized by spectral cytometry analysis and immunofluorescence assays in esophageal biopsies from 7 healthy controls and 13 EoE patients. Results: Interestingly, EoE patients at baseline had lower levels of circulating pDC compared with controls. Before treatment, patients with EoE who responded to PPI therapy had higher levels of circulating pDC and classical monocytes, compared with non-responders. Moreover, following PPI therapy pDC levels were increased in all EoE patients, while normal levels were only restored in PPI-responding patients. Finally, circulating pDC levels inversely correlated with peak eosinophil count and pDC count in esophageal biopsies. The number of tissue pDCs significantly increased during active EoE, being even higher in non-responder patients when compared to responder patients pre-PPI. pDC levels decreased after PPI intake, being further restored almost to control levels in responder patients post-PPI. Conclusions: We hereby describe a unique immune fingerprint of EoE patients at diagnosis. Moreover, circulating pDC may be also used as a novel non-invasive biomarker to predict subsequent response to PPI treatment.

A genome-wide association study for survival from a multi-centre European study identified variants associated with COVID-19 risk of death.

The clinical manifestations of SARS-CoV-2 infection vary widely among patients, from asymptomatic to life-threatening. Host genetics is one of the factors that contributes to this variability as previously reported by the COVID-19 Host Genetics Initiative (HGI), which identified sixteen loci associated with COVID-19 severity. Herein, we investigated the genetic determinants of COVID-19 mortality, by performing a case-only genome-wide survival analysis, 60 days after infection, of 3904 COVID-19 patients from the GEN-COVID and other European series (EGAS00001005304 study of the COVID-19 HGI). Using imputed genotype data, we carried out a survival analysis using the Cox model adjusted for age, age2, sex, series, time of infection, and the first ten principal components. We observed a genome-wide significant (P-value < 5.0 × 10-8) association of the rs117011822 variant, on chromosome 11, of rs7208524 on chromosome 17, approaching the genome-wide threshold (P-value = 5.19 × 10-8). A total of 113 variants were associated with survival at P-value < 1.0 × 10-5 and most of them regulated the expression of genes involved in immune response (e.g., CD300 and KLR genes), or in lung repair and function (e.g., FGF19 and CDH13). Overall, our results suggest that germline variants may modulate COVID-19 risk of death, possibly through the regulation of gene expression in immune response and lung function pathways.

Serum and Urine Metabolomic Profiling of Newly Diagnosed Treatment-Naïve Inflammatory Bowel Disease Patients.

BACKGROUND AND AIMS: Inflammatory bowel disease (IBD) is a prevalent chronic noncurable disease associated with profound metabolic changes. The discovery of novel molecular indicators for unraveling IBD etiopathogenesis and the diagnosis and prognosis of IBD is therefore pivotal. We sought to determine the distinctive metabolic signatures from the different IBD subgroups before treatment initiation. METHODS: Serum and urine samples from newly diagnosed treatment-naïve IBD patients and age and sex-matched healthy control (HC) individuals were investigated using proton nuclear magnetic resonance spectroscopy. Metabolic differences were identified based on univariate and multivariate statistical analyses. RESULTS: A total of 137 Crohn's disease patients, 202 ulcerative colitis patients, and 338 HC individuals were included. In the IBD cohort, several distinguishable metabolites were detected within each subgroup comparison. Most of the differences revealed alterations in energy and amino acid metabolism in IBD patients, with an increased demand of the body for energy mainly through the ketone bodies. As compared with HC individuals, differences in metabolites were more marked and numerous in Crohn's disease than in ulcerative colitis patients, and in serum than in urine. In addition, clustering analysis revealed 3 distinct patient profiles with notable differences among them based on the analysis of their clinical, anthropometric, and metabolomic variables. However, relevant phenotypical differences were not found among these 3 clusters. CONCLUSIONS: This study highlights the molecular alterations present within the different subgroups of newly diagnosed treatment-naïve IBD patients. The metabolomic profile of these patients may provide further understanding of pathogenic mechanisms of IBD subgroups. Serum metabotype seemed to be especially sensitive to the onset of IBD.

IL-6 promotes immune responses in human ulcerative colitis and induces a skin-homing phenotype in the dendritic cells and Tcells they stimulate.

Dendritic cells (DCs) control the type and location of immune responses. Ulcerative colitis (UC) is considered a Th2 disease mediated by IL-13 where up to one third of patients can develop extraintestinal manifestations. Colonic biopsies from inflamed and noninflamed areas of UC patients were cultured in vitro and their supernatants were used to condition human blood enriched DCs from healthy controls. Levels of IL-13 in the culture supernatants were below the detection limit in most cases and the cytokine profile suggested a mixed profile rather than a Th2 cytokine profile. IL-6 was the predominant cytokine found in inflamed areas from UC patients and its concentration correlated with the Mayo endoscopic score for severity of disease. DCs conditioned with noninflamed culture supernatants acquired a regulatory phenotype with decreased stimulatory capacity. However, DCs conditioned with inflamed culture supernatants acquired a proinflammatory phenotype with increased expression of the skin-homing chemokine CCR8. These DCs did not have decreased T-cell stimulatory capacity and primed T cells with the skin-homing CLA molecule in an IL-6-dependent mechanism. Our results highlight the role of IL-6 in UC and question the concept of UC as a Th2 disease and the relevance of IL-13 in its etiology.

Dysregulated circulating dendritic cell function in ulcerative colitis is partially restored by probiotic strain Lactobacillus casei Shirota.

BACKGROUND: Dendritic cells regulate immune responses to microbial products and play a key role in ulcerative colitis (UC) pathology. We determined the immunomodulatory effects of probiotic strain Lactobacillus casei Shirota (LcS) on human DC from healthy controls and active UC patients. METHODS: Human blood DC from healthy controls (control-DC) and UC patients (UC-DC) were conditioned with heat-killed LcS and used to stimulate allogeneic T cells in a 5-day mixed leucocyte reaction. RESULTS: UC-DC displayed a reduced stimulatory capacity for T cells (P < 0.05) and enhanced expression of skin-homing markers CLA and CCR4 on stimulated T cells (P < 0.05) that were negative for gut-homing marker ß7. LcS treatment restored the stimulatory capacity of UC-DC, reflecting that of control-DC. LcS treatment conditioned control-DC to induce CLA on T cells in conjunction with ß7, generating a multihoming profile, but had no effects on UC-DC. Finally, LcS treatment enhanced DC ability to induce TGFß production by T cells in controls but not UC patients. CONCLUSIONS: We demonstrate a systemic, dysregulated DC function in UC that may account for the propensity of UC patients to develop cutaneous manifestations. LcS has multifunctional immunoregulatory activities depending on the inflammatory state; therapeutic effects reported in UC may be due to promotion of homeostasis.