During colonization of germfree mice with the total fecal microbial community of their conventionally born and raised siblings (conventionalization), the intestinal mucosal immune system initiates ...and maintains a balanced immune response. However, the genetic regulation of these balanced, appropriate responses to the microbiota is obscure. Here, combined analysis of germfree and conventionalized mice revealed that the major molecular responses could be detected initiating at day 4 post conventionalization, with a strong induction of innate immune functions followed by stimulation of adaptive immune responses and development and expansion of adaptive immune cells at later stages of conventionalization. This study provides a comprehensive overview of mouse developmental and immune-related cellular pathways and processes that were co-mediated by the commensal microbiota and suggests which mechanisms were involved in this reprogramming. The dynamic, region-dependent mucosal responses to the colonizing microbiota revealed potential transcriptional signatures for the control of intestinal homeostasis in healthy mice, which may help to decipher the genetic basis of pathway dysregulation in human intestinal inflammatory diseases.
CD103
CD11b
dendritic cells (DCs) are unique to the intestine, but the factors governing their differentiation are unclear. Here we show that transforming growth factor receptor 1 (TGFβR1) has an ...indispensable, cell intrinsic role in the development of these cells. Deletion of Tgfbr1 results in markedly fewer intestinal CD103
CD11b
DCs and a reciprocal increase in the CD103
CD11b
dendritic cell subset. Transcriptional profiling identifies markers that define the CD103
CD11b
DC lineage, including CD101, TREM1 and Siglec-F, and shows that the absence of CD103
CD11b
DCs in CD11c-Cre.Tgfbr1
mice reflects defective differentiation from CD103
CD11b
intermediaries, rather than an isolated loss of CD103 expression. The defect in CD103
CD11b
DCs is accompanied by reduced generation of antigen-specific, inducible FoxP3
regulatory T cells in vitro and in vivo, and by reduced numbers of endogenous Th17 cells in the intestinal mucosa. Thus, TGFβR1-mediated signalling may explain the tissue-specific development of these unique DCs.Developmental cues for the different dendritic cell (DC) subsets in the intestine are yet to be defined. Here the authors show that TGFβR1 signalling is needed for development of CD103
CD11b
intestinal DCs from CD103
CD11b
cells and that they contribute to the generation of Th17 and regulatory T cells.
Uncontrolled interferon γ (IFNγ)-mediated T-cell responses to commensal microbiota are a driver of inflammatory bowel disease (IBD). Interleukin-10 (IL-10) is crucial for controlling these T-cell ...responses, but the precise mechanism of inhibition remains unclear. A better understanding of how IL-10 exerts its suppressive function may allow identification of individuals with suboptimal IL-10 function among the heterogeneous population of IBD patients. Using cells from patients with an IL10RA deficiency or STAT3 mutations, we demonstrate that IL-10 signaling in monocyte-derived dendritic cells (moDCs), but not T cells, is essential for controlling IFNγ-secreting CD4
T cells. Deficiency in IL-10 signaling dramatically increased IL-1β release by moDCs. IL-1β boosted IFNγ secretion by CD4
T cells either directly or indirectly by stimulating moDCs to secrete IL-12. As predicted a signature of IL-10 dysfunction was observed in a subgroup of pediatric IBD patients having higher IL-1β expression in activated immune cells and macroscopically affected intestinal tissue. In agreement, reduced IL10RA expression was detected in peripheral blood mononuclear cells and a subgroup of pediatric IBD patients exhibited diminished IL-10 responsiveness. Our data unveil an important mechanism by which IL-10 controls IFNγ-secreting CD4
T cells in humans and identifies IL-1β as a potential classifier for a subgroup of IBD patients.
The intestinal influx oligopeptide transporter peptide transporter 1 (PEPT1) (SLC15A1) is best known for nutrient-derived di- and tripeptide transport. Its role in drug absorption is increasingly ...recognized. To better understand the disposition of PEPT1 substrate drugs in young infants, we studied intestinal PEPT1 mRNA expression and tissue localization across the pediatric age range. PEPT1 mRNA expression was determined using real-time reverse-transcription polymerase chain reaction in small intestinal tissues collected from surgical procedures (neonates and infants) or biopsies (older children and adolescents). PEPT1 mRNA relative to villin mRNA expression was compared between neonates/infants and older children/adolescents. PEPT1 was visualized in infant tissue using immunohistochemical staining. Other transporters multidrug resistance protein 1 (MDR1), multidrug resistance-like protein 2 (MRP2), and organic anion transporter polypeptide 2B1 (OATP2B1) were also stained to describe the localization in relation to PEPT1. Twenty-six intestinal samples (n = 20 neonates/infants, n = 2 pediatric, n = 4 adolescents) were analyzed. The young infant samples were collected at a median (range) gestational age at birth of 29.2 weeks (24.7-40) and postnatal age of 2.4 weeks (0-16.6). The PEPT1 mRNA expression of the neonates/infants was only marginally lower (0.8-fold) than the older children (P < 0.05). Similar and clear apical PEPT1 and MRP2 staining, apical and lateral MDR1 staining, and intraepithelial OATP2B1 staining at the basolateral membrane of the enterocyte were detected in 12 infant and 2 adolescent samples. Although small intestinal PEPT1 expression tended to be lower in neonates than in older children, this difference is small and tissue distribution is similar. This finding suggests similar oral absorption of PEPT1 substrates across the pediatric age range.
Breach of tolerance to gluten leads to the chronic small intestinal enteropathy celiac disease. A key event in celiac disease development is gluten-dependent infiltration of activated cytotoxic ...intraepithelial lymphocytes (IELs), which cytolyze epithelial cells causing crypt hyperplasia and villous atrophy. The mechanisms leading to gluten-dependent small intestinal IEL infiltration and activation remain elusive. We have demonstrated that under homeostatic conditions in mice, gluten drives the differentiation of anti-inflammatory T cells producing large amounts of the immunosuppressive cytokine interleukin-10 (IL-10). Here we addressed whether this dominant IL-10 axis prevents gluten-dependent infiltration of activated cytotoxic IEL and subsequent small intestinal enteropathy. We demonstrate that IL-10 regulation prevents gluten-induced cytotoxic inflammatory IEL infiltration. In particular, IL-10 suppresses gluten-induced accumulation of a specialized population of cytotoxic CD4
CD8αα
IEL (CD4
CTL) expressing Tbx21, Ifng, and Il21, and a disparate non-cytolytic CD4
CD8α
IEL population expressing Il17a, Il21, and Il10. Concomitantly, IL-10 suppresses gluten-dependent small intestinal epithelial hyperproliferation and upregulation of stress-induced molecules on epithelial cells. Remarkably, frequencies of granzyme B
CD4
CD8α
IEL are increased in pediatric celiac disease patient biopsies. These findings demonstrate that IL-10 is pivotal to prevent gluten-induced small intestinal inflammation and epithelial damage, and imply that CD4
CTL are potential new players into these processes.
Antibodies directed to tumour necrosis factor-α (TNF-α) are very effective in treating paediatric Crohn’s disease (CD). Over the last few years, research has provided important new insights into how ...to optimise this treatment’s effectiveness. Research on predictors for anti-TNF treatment responsiveness has revealed potential markers, but data on their accuracy in paediatric CD patients are lagging behind. Also, new evidence has become available on the safety profile of anti-TNF antibodies that suggests the assumed increased malignancy risk seen in patients on anti-TNF and thiopurine combination treatment may be linked more to thiopurine use and not to anti-TNF treatment. In addition, the early results of CT-P13, an infliximab biosimilar, in CD patients confirm the expected similarity with its originator. Thus, the effectiveness of anti-TNF antibody treatment is slowly improving, its malignancy risk is lower than assumed, and its costs are reduced by the introduction of equally effective biosimilars. Together, these trends allow for a more prominent role for anti-TNF antibodies in future treatment of paediatric CD.
To cite this article: du Pré MF, Samsom JN. Adaptive T-cell responses regulating oral tolerance to protein antigen. Allergy 2011; 66: 478-490. ABSTRACT: The term oral (or mucosal) tolerance has been ...classically defined as the suppression of T- and B-cell responses to an antigen by prior administration of the antigen by the oral route. In recent years, it has become clear that both innate and acquired regulatory immune responses are essential for the development of oral tolerance. As such, mucosal microenvironmental factors such as transforming growth factor- β, prostaglandins but also dietary vitamin A create conditioning of an adaptive regulatory T-cell response that suppresses subsequent antigen-specific responses. Particular resident subsets of antigen presenting dendritic cells are pivotal to convey conditioning signals next to the presentation of antigen. This review discusses the primary mechanisms of adaptive regulatory T-cell induction to ingested soluble protein antigen. However, we also discuss the limitations of our knowledge with respect to understanding the very common food hypersensitivity Celiac disease caused by an aberrant adaptive immune response to the food protein gluten.
Tolerance to harmless exogenous antigens is the default immune response in the gastrointestinal tract. Although extensive studies have demonstrated the importance of the mesenteric lymph nodes (MLNs) ...and intestinal CD103(+) dendritic cells (DCs) in driving small intestinal tolerance to protein antigen, the structural and immunological basis of colonic tolerance remain poorly understood. We show here that the caudal and iliac lymph nodes (ILNs) are inductive sites for distal colonic immune responses and that colonic T cell-mediated tolerance induction to protein antigen is initiated in these draining lymph nodes and not in MLNs. In agreement, colonic tolerance induction was not altered by mesenteric lymphadenectomy. Despite tolerance development, CD103(+)CD11b(+) DCs, which are the major migratory DC population in the MLNs, and the tolerance-related retinoic acid-generating enzyme RALDH2 were virtually absent from the ILNs. Administration of ovalbumin (OVA) to the distal colon did increase the number of CD11c(+)MHCII(hi) migratory CD103(-)CD11b(+) and CD103(+)CD11b(-) DCs in the ILNs. Strikingly, colonic tolerance was intact in Batf3-deficient mice specifically lacking CD103(+)CD11b(-) DCs, suggesting that CD103(-) DCs in the ILNs are sufficient to drive tolerance induction after protein antigen encounter in the distal colon. Altogether, we identify different inductive sites for small intestinal and colonic T-cell responses and reveal that distinct cellular mechanisms are operative to maintain tolerance at these sites.
Summary
We hypothesize that T cells such as interleukin (IL)‐21+B cell lymphoma 6 (BCL6)+ T follicular helper cells can regulate B cell‐mediated immunity within the allograft during acute T ...cell‐mediated rejection; this process may feed chronic allograft rejection in the long term. To investigate this mechanism, we determined the presence and activation status of organized T and B cells in so‐called ectopic lymphoid structures (ELSs) in different types of acute renal allograft rejection. Biopsies showing the following primary diagnosis were included: acute/active antibody‐mediated rejection, C4d+ (a/aABMR), acute T cell‐mediated rejection grade I (aTCMRI) and acute T cell‐mediated rejection grade II (aTCMRII). Paraffin sections were stained for T cells (CD3 and CD4), B cells (CD20), follicular dendritic cells (FDCs, CD23), activated B cells (CD79A), immunoglobulin (Ig)D, cell proliferation (Ki67) and double immunofluorescent stainings for IL‐21 and BCL6 were performed. Infiltrates of T cells were detected in all biopsies. In aTCMRI, B cells formed aggregates surrounded by T cells. In these aggregates, FDCs, IgD and Ki67 were detected, suggesting the presence of ELSs. In contrast, a/aABMR and aTCMRII showed diffuse infiltrates of T and B cells but no FDCs and IgD. IL‐21 was present in all biopsies. However, co‐localization with BCL6 was observed mainly in aTCMRI biopsies. In conclusion, ELSs with an activated phenotype are found predominantly in aTCMRI where T cells co‐localize with B cells. These findings suggest a direct pathway of B cell alloactivation at the graft site during T cell mediated rejection.
In this manuscript we hypothesize that T cells such as IL‐21+BCL6+ T follicular helper cells can regulate B cell mediated immunity within the renal allograft during acute T‐cell mediated rejection, this process may feed chronic allograft rejection on long term. To investigate this mechanism we determined the presence and activation status of organized T and B cells in so‐called ectopic lymphoid structures (ELSs) in different types of acute renal allograft rejection. ELSs with an activated phenotype are predominantly found in acute T cell‐mediated rejection grade I (aTCMRI), suggesting a direct pathway of B cell allo‐activation at the graft site during T cell mediated rejection.
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