Explore the vast range of titles available.

Mucosal-Associated Invariant T (MAIT) cells are T cells with a semi-invariant T cell receptor (TCR), recognizing riboflavin precursors presented by a non-polymorphic MR1 molecule. As these precursors are produced by the gut microbiome, we characterized the frequency, phenotype and clonality of MAIT cells in human colons with and without Crohn's disease (CD). The transcriptome of MAIT cells sorted from blood and intestinal lamina propria cells from colectomy recipients were compared with other CD8.sup.+ T cells. Colon biopsies from an additional ten CD patients and ten healthy controls (HC) were analyzed by flow cytometry. TCR genes were sequenced from individual MAIT cells from these biopsies and compared with those of MAIT cells from autologous blood. MAIT cells in the blood and colon showed a transcriptome distinct from other CD8 T cells, with more expression of the IL-23 receptor. MAIT cells were enriched in the colons of CD patients, with less NKG2D in inflamed versus uninflamed segments. Regardless of disease, most MAIT cells expressed integrin [alpha]4[beta]7 in the colon but not in the blood, where they were enriched for [alpha]4[beta]7 expression. TCR sequencing revealed heterogeneity in the colon and blood, with few public sequences associated with cohorts. MAIT cells are enriched in the colons of CD patients and disproportionately express molecules (IL-23R, integrin [alpha]4[beta]7) targeted by CD therapeutics, to suggest a pathogenic role for them in CD. Public TCR sequences were neither common nor sufficiently restricted to a cohort to suggest protective or pathogenic antigen-specificities.

FOXP3+ regulatory T cells (Tregs) are critical for preventing intestinal inflammation. However, FOXP3+ T cells are paradoxically increased in the intestines of patients with the inflammatory bowel disease (IBD) ulcerative colitis (UC) or Crohn's disease (CD). We determined whether these FOXP3+ cells in IBD patients share or lack the phenotype of such cells from patients without IBD. We quantified and characterized FOXP3+ Treg populations, as well as FOXP3- CD4+ T cells, in the lamina propria lymphocytes (LPL) of intestine surgically resected from patients with and without IBD, and in the blood of controls or Crohn's patients with or without disease activity. In all samples, a similar fraction of FOXP3+ cells expressed the \"natural\" Treg (nTreg) marker Helios, suggesting that, in IBD, these cells are not entirely \"induced\" Tregs (iTregs) derived from activated effector T cells. Helios+ and Helios- FOXP3+ T cells demonstrated similar expression of maturation markers, activation markers, and inhibitory molecules between IBD patients and controls, while FOXP3- cells paradoxically expressed more of the inhibitory receptors CD39, CTLA4, and PD-1 in inflamed mucosa. Greater expression of activation markers was also seen in both Helios+ and Helios- Tregs, relative to FOXP3- cells, in both IBD patients and controls, indicating that Tregs are effectively activated by antigen in IBD. Extensive immunophenotyping revealed that Helios+ and Helios- mucosal Tregs exist at a similar frequency, and have a similar expression of inhibitory molecules and activation markers in patients with IBD as in healthy controls.

Background/AimsVedolizumab is an anti-α4β7 monoclonal antibody approved for the treatment of inflammatory bowel disease (IBD). This exploratory study aimed to identify biomarkers associated with vedolizumab response.MethodsTwenty-six IBD patients (15 with Crohn’s, 11 with ulcerative or indeterminate colitis) initiating vedolizumab at a single center between 2014 and 2016 underwent sampling of serum and peripheral blood mononuclear cells (PBMCs) before and during vedolizumab therapy. Response was defined as steroid-free improvement in endoscopic score or Harvey–Bradshaw index/simple clinical colitis activity index (reduction greater than 3 or total less than 3). PBMCs were evaluated for immunophenotype and expression of α4β7 integrin on lymphocytes before and during vedolizumab therapy. Serum vedolizumab levels and α4β7 saturation were measured serially after induction.ResultsFourteen out of 26 (54%) patients treated with vedolizumab responded to therapy. Pretreatment α4β7 expression was higher in responders on multiple subsets of T, B, and NK cells, with terminal effector memory (p = .0009 for CD4 and .0043 for CD8) and NK cells (p = .0047) best discriminating between responders and nonresponders. During therapy, log10 serum vedolizumab levels at trough were higher in responders than nonresponders (p = .0007). Conversely, the percentage of effector memory T cells with free α4β7 at trough was lower in responders than nonresponders (p < .0001). However, loss of α4β7 saturation with vedolizumab was more sensitive to low serum vedolizumab in nonresponders.ConclusionsPretreatment α4β7 expression and α4β7 receptor saturation during maintenance therapy were identified as candidate biomarkers for vedolizumab response.

Abstract Background Vedolizumab, an antibody blocking integrin α4β7, is a safe and effective therapy for Crohn’s disease and ulcerative colitis. Blocking α4β7 from binding its cognate addressin MAdCAM-1 on intestinal blood vessel endothelial cells prevents T cells from migrating to the gut mucosa in animal models. However, data supporting this mechanism of action in humans is limited. Methods We conducted a cross-sectional case-control study to evaluate the effect of vedolizumab on intestinal immune cell populations while avoiding the confounding effect of resolving inflammation on the cellularity of the colonic mucosa in treatment-responsive patients. Colon biopsies from 65 case subjects receiving vedolizumab were matched with biopsies from 65 control individuals, similar in disease type, medications, anatomic location, and inflammation. Biopsies were analyzed by flow cytometry and full messenger RNA transcriptome sequencing of sorted T cells. Results No difference was seen between vedolizumab recipients and control individuals in the quantity of any antigen-experienced T lymphocyte subset or in the quality of the transcriptome in any experienced T cell subset. Fewer naïve colonic B and T cells were seen in vedolizumab recipients than control individuals, regardless of response. However, the most striking finding was a marked reduction in CD1c+ (BDCA1+) dendritic cells exclusively in vedolizumab-responsive patients. In blood, these dendritic cells ubiquitously express high levels of α4β7, which is rapidly downregulated upon vedolizumab exposure. Conclusions The clinical effects of vedolizumab reveal integrin α4β7-dependent dendritic cell migration to the intestinal mucosa to be central to inflammatory bowel disease pathogenesis. Lay Summary Vedolizumab had no effect on the number or gene expression of memory T lymphocytes in the colons of recipients relative to control individuals. However, the colons of vedolizumab-responsive patients had distinctly fewer dendritic cells, which in blood express the most integrin α4β7.

Successful treatment of inflammatory bowel disease (IBD) with the anti-integrin α4β7 mAb vedolizumab suggests that interaction of this integrin with addressin mucosal addressin cell adhesion molecule-1 (MAdCAM-1) is central to IBD pathogenesis. Although this was presumed to be due to an inhibition of lymphocyte trafficking to the gut, as has been observed in animal models, we report no depletion of CD4 T cells from the colonic mucosa as a consequence of vedolizumab treatment in humans, regardless of efficacy. Likewise, no upregulation of alternative trafficking mechanisms was observed as a consequence of therapy to suggest that this homeostasis is maintained in patients by a mechanistic escape from inhibition. Instead, we explore a role for MAdCAM–integrin interaction as a gut-specific costimulatory signal, demonstrating that it can replace CD28 ligation to activate human T cells in vitro. This activation through integrin α4β7 is mediated through the gut-restricted molecule MAdCAM-1, and it cannot be replicated by matrix molecules or proteins that bind other integrins. A detailed analysis of mRNA expression by human T cell subsets following suboptimal TCR stimulation in the presence or absence of CD28 versus MAdCAM-1 costimulation reveals marked similarity in the effect that these two signals have upon T cells, with temporal or quantitative differences detected in the expression of cytokines associated with Th17 cells or pyogenic inflammation. Thus, we describe an alternative costimulatory pathway for T cells in the intestine, through ligation of integrin α4β7 by MAdCAM-1, which may explain the therapeutic efficacy of vedolizumab and have implications concerning the treatment of IBD.

Ulcerative colitis (UC) is characterized by epithelial barrier dysfunction and dysregulated mucosal immune responses; however, the mechanisms driving disease onset remain poorly defined. Autoantibodies against the epithelial-restricted integrin αvβ6 are a highly specific biomarker of UC that can precede clinical diagnosis by up to 10 years. Because αvβ6 activates TGFβ at epithelial surfaces, we hypothesized that UC-associated αvβ6 autoantibodies inhibit mucosal TGFβ activation and disrupt epithelial homeostasis. We showed that αvβ6 autoantibodies were enriched in UC and that IgG from autoantibody-positive individuals inhibited αvβ6-dependent activation of TGFβ. αvβ6 blockade dampened TGFβ signaling and altered differentiation-associated gene programs in human intestinal epithelial cells. In mice, deletion of αv caused expansion of inflammation-associated goblet cells in the colon and changes in intestinal immune cells. Using a novel mouse model, we showed that αvβ6-specific autoantibody disrupted epithelial-immune crosstalk and increased susceptibility to DSS colitis. Together, these findings establish anti-αvβ6 autoantibodies as active inhibitors of epithelial TGFβ signaling, constituting a anti-cytokine response, rather than passive biomarkers. By linking preclinical seropositivity to impaired epithelial signaling and heightened susceptibility to colitis, this work identifies epithelial αvβ6-dependent TGFβ activation as a pathway that may be leveraged to modify disease risk or limit disease severity.

Successful treatment of inflammatory bowel disease (IBD) with the anti-integrin α β mAb vedolizumab suggests that interaction of this integrin with addressin mucosal addressin cell adhesion molecule-1 (MAdCAM-1) is central to IBD pathogenesis. Although this was presumed to be due to an inhibition of lymphocyte trafficking to the gut, as has been observed in animal models, we report no depletion of CD4 T cells from the colonic mucosa as a consequence of vedolizumab treatment in humans, regardless of efficacy. Likewise, no upregulation of alternative trafficking mechanisms was observed as a consequence of therapy to suggest that this homeostasis is maintained in patients by a mechanistic escape from inhibition. Instead, we explore a role for MAdCAM-integrin interaction as a gut-specific costimulatory signal, demonstrating that it can replace CD28 ligation to activate human T cells in vitro. This activation through integrin α β is mediated through the gut-restricted molecule MAdCAM-1, and it cannot be replicated by matrix molecules or proteins that bind other integrins. A detailed analysis of mRNA expression by human T cell subsets following suboptimal TCR stimulation in the presence or absence of CD28 versus MAdCAM-1 costimulation reveals marked similarity in the effect that these two signals have upon T cells, with temporal or quantitative differences detected in the expression of cytokines associated with Th17 cells or pyogenic inflammation. Thus, we describe an alternative costimulatory pathway for T cells in the intestine, through ligation of integrin α β by MAdCAM-1, which may explain the therapeutic efficacy of vedolizumab and have implications concerning the treatment of IBD.

Background FOXP3+ regulatory T cells (Tregs) are critical for preventing intestinal inflammation. However, FOXP3+ T cells are paradoxically increased in the intestines of patients with the inflammatory bowel disease (IBD) ulcerative colitis (UC) or Crohn's disease (CD). We determined whether these FOXP3+ cells in IBD patients share or lack the phenotype of such cells from patients without IBD. Methods We quantified and characterized FOXP3+ Treg populations, as well as FOXP3- CD4+ T cells, in the lamina propria lymphocytes (LPL) of intestine surgically resected from patients with and without IBD, and in the blood of controls or Crohn's patients with or without disease activity. Results In all samples, a similar fraction of FOXP3+ cells expressed the \"natural\" Treg (nTreg) marker Helios, suggesting that, in IBD, these cells are not entirely \"induced\" Tregs (iTregs) derived from activated effector T cells. Helios+ and Helios- FOXP3+ T cells demonstrated similar expression of maturation markers, activation markers, and inhibitory molecules between IBD patients and controls, while FOXP3- cells paradoxically expressed more of the inhibitory receptors CD39, CTLA4, and PD-1 in inflamed mucosa. Greater expression of activation markers was also seen in both Helios+ and Helios- Tregs, relative to FOXP3- cells, in both IBD patients and controls, indicating that Tregs are effectively activated by antigen in IBD. Conclusions Extensive immunophenotyping revealed that Helios+ and Helios- mucosal Tregs exist at a similar frequency, and have a similar expression of inhibitory molecules and activation markers in patients with IBD as in healthy controls.

Autophagy proteins have been linked with development of immune-mediated diseases including lupus, but the mechanisms for this are unclear. We have previously shown that non-canonical autophagy induced by αv-integrins regulates B cell activation by viral and self-antigens in mice. Here we investigated the involvement of this pathway in B cells from human tissue. Our data revealed that autophagy is specifically induced in germinal-center and memory B cell sub-populations from human tonsil and spleen. Transcriptomic analysis showed that induction of autophagy is related to unique aspects of activated B cells such as mitochondrial metabolism. To understand the function of non-canonical autophagy in B cells, we used CRISPR-mediated knockdown of autophagy genes. Integrating data from primary B cells and knockout cells we found that αv-integrin-related non-canonical autophagy limits activation of specific pathways while promoting others. These data provide new mechanistic links for autophagy and immune dysregulation in diseases such as lupus.