Jan Hendrik Niess

Commensal Gut Flora Drives the Expansion of Proinflammatory CD4 T Cells in the Colonic Lamina Propria under Normal and Inflammatory Conditions

We tested in B6 mice whether the local expansion of CD4 T cells producing proinflammatory cytokines including IL-17 (Th17 cells) in the colonic lamina propria (cLP) depends on the commensal microflora. High numbers of CD4 Th17 cells were found in the lamina propria of the ileum and colon but not the duodenum, jejunum, mesenteric lymph nodes, spleen, or liver of specific pathogen-free (SPF) mice. The microflora is required for the accumulation of cytokine (IL-17, IFN-γ, TNF-α, IL-10)-producing CD4 T cells in the cLP because only low numbers of cytokine-producing cLP CD4 T cells were found in syngeneic (age- and sex-matched) germfree mice. The fraction of cLP Th17 cells was higher in (type I and type II) IFN- but not IL-4- or IL-12p40-deficient SPF congenics. cLP CD4 Th17 cells produce IL-17 but not IFN-γ, TNF-α, IL-4, or IL-10. cLP CD4 Th17 cells accumulate locally in colitis induced by adoptive transfer of IFN-γ+/+ or IFN-γ−/− CD4 T cells into congenic SPF (but not germfree) RAG−/− hosts. In this colitis model, cLP CD4 T cells that “spontaneously” produce IL-17 progressively increase in number in the inflamed cLP, and increasing serum IL-17 levels appear as the disease progresses. Commensal bacteria-driven, local expansion of cLP CD4 Th17 cells may contribute to the pathogenesis of this inflammatory bowel disease.

Enteric Flora Expands Gut Lamina Propria CX3CR1+ Dendritic Cells Supporting Inflammatory Immune Responses under Normal and Inflammatory Conditions

CD103 or CX3CR1 surface expression defines distinct dendritic cells (DCs) and macrophages in the murine lamina propria of the colon (cLP). We investigated the surface marker and functional phenotype of CD103+ and CX3CR1+ cLP DCs and their role in transfer colitis. cLP CD11c+ cells were isolated from specific pathogen-free or germ-free mice to elucidate the role of the commensal flora in their development. The cLP CD11c+ cells are a heterogeneous cell population that includes 16% CX3CR1+, 34% CD103+, 30% CD103−CX3CR1− DCs, and 17% CD68+/F4/80+CX3CR1+CD11c+ macrophages. All DCs expressed high levels of MHC II but low levels of costimulatory (CD40, CD86, and CD80) and coinhibitory (programmed death ligand-1) molecules. Ex vivo confocal microscopy demonstrated that CX3CR1+CD11c+ cells, but not CD103+ DCs, were reduced in the cLP of germ-free (CX3CR1-GFP) mice. The absence of the enteric flora prevents the formation of transepithelial processes by the CX3CR1+ DCs. CX3CR1+ DCs preferentially supported Th1/Th17 CD4 T cell differentiation. CD103+ DCs preferentially induced the differentiation of Foxp3-expressing regulatory T cells. The stimulation of cLP DCs with fractalkine/CX3CL1 increased the release of IL-6 and TNF-α. In the absence of CX3CR1, the CD45RBhigh CD4 transfer colitis was suppressed and associated with reduced numbers of DCs in the mesenteric lymph nodes and a reduction in serum IFN-γ and IL-17. The local bacteria-driven accumulation of CX3CR1+ DCs seems to support inflammatory immune responses.

CD69 Regulates Type I IFN-Induced Tolerogenic Signals to Mucosal CD4 T Cells That Attenuate Their Colitogenic Potential

CD69 is highly expressed by lymphocytes at mucosal surfaces. We aimed to investigate the role of CD69 in mucosal immune responses. The expression of CD69 by CD4 T cells isolated from the spleen, mesenteric lymph nodes, small intestinal lamina propria, and colonic lamina propria was determined in specific pathogen-free B6 and TCR transgenic animals, as well as in germ-free B6 mice. Transfer colitis was induced by transplanting RAG−/− mice with B6 or CD69−/−CD45RBhigh CD4 T cells. CD69 expression by CD4 T cells is induced by the intestinal microflora, oral delivery of specific Ag, and type I IFN (IFN-I) signals. CD4 T cells from CD69−/− animals produce higher amounts of the proinflammatory cytokines IFN-γ, TNF-α, and IL-21, whereas the production of TGF-β1 is decreased. CD69-deficient CD4 T cells showed reduced potential to differentiate into Foxp3+ regulatory T cells in vivo and in vitro. The transfer of CD69−/−CD45RBhigh CD4 T cells into RAG−/− hosts induced an accelerated colitis. Oral tolerance was impaired in CD69−/− and IFN-I receptor 1-deficient mice when compared with B6 and OT-II × RAG−/− animals. Polyinosinic-polycytidylic acid treatment of RAG−/− mice transplanted with B6 but not CD69−/− or IFN-I receptor 1-deficient CD45RBhigh CD4 T cells attenuated transfer colitis. CD69 deficiency led to the increased production of proinflammatory cytokines, reduced Foxp3+ regulatory T cell induction, impaired oral tolerance, and more severe colitis. Hence, the activation Ag CD69 plays an important role in regulating mucosal immune responses.

Tissue-specific differentiation of a circulating CCR9 − pDC-like common dendritic cell precursor

The ontogenic relationship between the common dendritic cell (DC) progenitor (CDP), the committed conventional DC precursor (pre-cDC), and cDC subpopulations in lymphoid and nonlymphoid tissues has been largely unraveled. In contrast, the sequential steps of plasmacytoid DC (pDC) development are less defined, and it is unknown at which developmental stage and location final commitment to the pDC lineage occurs. Here we show that CCR9(-) pDCs from murine BM which enter the circulation and peripheral tissues have a common DC precursor function in vivo in the steady state, in contrast to CCR9(+) pDCs which are terminally differentiated. On adoptive transfer, the fate of CCR9(-) pDC-like precursors is governed by the tissues they enter. In the BM and liver, most transferred CCR9(-) pDC-like precursors differentiate into CCR9(+) pDCs, whereas in peripheral lymphoid organs, lung, and intestine, they additionally give rise to cDCs. CCR9(-) pDC-like precursors which are distinct from pre-cDCs can be generated from the CDP. Thus, CCR9(-) pDC-like cells are novel CDP-derived circulating DC precursors with pDC and cDC potential. Their final differentiation into functionally distinct pDCs and cDCs depends on tissue-specific factors allowing adaptation to local requirements under homeostatic conditions.

Gut Microbiota, Probiotics and Inflammatory Bowel Disease

The colonization of humans with commensals is critical for our well-being. This tightly regulated symbiotic relationship depends on the flora and an intact mucosal immune system. A disturbance of either compound can cause intestinal inflammation. This review summarizes extrinsic and intrinsic factors contributing to intestinal dysbiosis and inflammatory bowel disease.

The Early Activation Marker CD69 Regulates the Expression of Chemokines and CD4 T Cell Accumulation in Intestine

Migration of naïve and activated lymphocytes is regulated by the expression of various molecules such as chemokine receptors and ligands. CD69, the early activation marker of C-type lectin domain family, is also shown to regulate the lymphocyte migration by affecting their egress from the thymus and secondary lymphoid organs. Here, we aimed to investigate the role of CD69 in accumulation of CD4 T cells in intestine using murine models of inflammatory bowel disease. We found that genetic deletion of CD69 in mice increases the expression of the chemokines CCL-1, CXCL-10 and CCL-19 in CD4+ T cells and/or CD4− cells. Efficient in vitro migration of CD69-deficient CD4 T cells toward the chemokine stimuli was the result of increased expression and/or affinity of chemokine receptors. In vivo CD69−/− CD4 T cells accumulate in the intestine in higher numbers than B6 CD4 T cells as observed in competitive homing assay, dextran sodium sulphate (DSS)-induced colitis and antigen-specific transfer colitis. In DSS colitis CD69−/− CD4 T cell accumulation in colonic lamina propria (cLP) was associated with increased expression of CCL-1, CXCL-10 and CCL-19 genes. Furthermore, treatment of DSS-administrated CD69−/− mice with the mixture of CCL-1, CXCL-10 and CCL-19 neutralizing Abs significantly decreased the histopathological signs of colitis. Transfer of OT-II×CD69−/− CD45RBhigh CD4 T cells into RAG−/− hosts induced CD4 T cell accumulation in cLP. This study showed CD69 as negative regulator of inflammatory responses in intestine as it decreases the expression of chemotactic receptors and ligands and reduces the accumulation of CD4 T cells in cLP during colitis.

What are CX3CR1+ mononuclear cells in the intestinal mucosa?

Intestinal dendritic cells (DC) and macrophages play a key role for the maintenance of intestinal integrity by initiating innate and adaptive immune responses. Although DC and macrophages have been viewed as distinct lineages, the reliability of surface markers for the definition of DC and macrophages has recently been questioned. Here, I will discuss the ontogeny and function of CX3CR1+ mononuclear cells in the small and large intestine.

Strongyloides stercoralis: a rare cause of obstructive duodenal stenosis.

Background: Strongyloidiasis is a rare helminthic infection in Europe, and it may cause duodenal obstruction. Methods: We report a patient who was admitted to our Medical Department with nausea and repeated vomiting since 10 years until food intake became impossible. Subsequent investigations revealed a duodenal obstruction at the upper third of the duodenum, as well as enterocolitis of the terminal ileum with eosinophils dispersed throughout the mucosa. Since food intake was still not possible after treatment with a course of i.v. PPI and prokinetic applications, we decided to perform a resection of the upper duodenum with Y-Roux reconstruction. Results: The histopathological examination of the resected specimen revealed strongyloidiasis. Conclusion: Parasite infections such as strongyloidiasis represent a rare differential diagnosis of duodenal obstruction especially if patients originate from endemic regions.

Age-of-onset-dependent influence of NOD2 gene variants on disease behaviour and treatment in Crohn’s disease

BackgroundInfluence of genetic variants in the NOD2 gene may play a more important role in disease activity, behaviour and treatment of pediatric- than adult-onset Crohn’s disease (CD).Methods85 pediatric- and 117 adult-onset CD patients were tested for the three main NOD2 CD-associated variants (p.R702W, p.G908R and p.10007fs) and clinical data of at least two years of follow-up were compared regarding disease behaviour and activity, response to therapy and bone mineral density (BMD).ResultsChronic active and moderate to severe course of CD is associated in patients with pediatric-onset (p=0.0001) and NOD2 variant alleles (p=0.0001). In pediatric-onset CD the average PCDAI-Score was significantly higher in patients carrying NOD2 variants (p=0.0008). In addition, underweight during course of the disease (p=0.012) was associated with NOD2 variants. Interestingly, osteoporosis was found more frequently in patients carrying NOD2 variant alleles (p=0.033), especially in pediatric-onset CD patients with homozygous NOD2 variants (p=0.037). Accordingly, low BMD in pediatric-onset CD is associated with a higher PCDAI (p=0.0092), chronic active disease (p=0.0148), underweight at diagnosis (p=0.0271) and during follow-up (p=0.0109). Furthermore, pediatric-onset CD patients with NOD2 variants are more frequently steroid-dependent or refractory (p=0.048) and need long-term immunosuppressive therapy (p=0.0213).ConclusionsThese data suggests that the presence of any of the main NOD2 variants in CD is associated with osteoporosis and an age of onset dependent influence towards underweight, higher disease activity and a more intensive immunosuppressive therapy. This observation supports the idea for an early intensive treatment strategy in children and adolescent CD patients with NOD2 gene variants.

Role of gut-resident dendritic cells in inflammatory bowel disease

The gastrointestinal immune system, innate and adaptive, is continuously exposed to challenges provided by the enteric flora. In most cases, the result of mucosal immune responses is the development of tolerance. Mucosal dendritic cells initiate and regulate local immune responses. Uncontrolled local immune responses are thought to be a major factor in the development of inflammatory bowel disease, such as Crohn’s disease and ulcerative colitis. This review will discuss the function of dendritic cells in the recognition of the enteric flora and their role in the development of intestinal inflammation.