Modulating microbiome-immune axis in the deployment-related chronic diseases of Veterans: report of an expert meeting

The present report summarizes the United States Department of Veterans Affairs (VA) field-based meeting titled "Modulating microbiome-immune axis in the deployment-related chronic diseases of Veterans." Our Veteran patient population experiences a high incidence of service-related chronic physical and mental health problems, such as infection, irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), various forms of hematological and non-hematological malignancies, neurologic conditions, end-stage organ failure, requiring transplantation, and posttraumatic stress disorder (PTSD). We report the views of a group of scientists who focus on the current state of scientific knowledge elucidating the mechanisms underlying the aforementioned disorders, novel therapeutic targets, and development of new approaches for clinical intervention. In conclusion, we dovetailed on four research areas of interest: 1) microbiome interaction with immune cells after hematopoietic cell and/or solid organ transplantation, graft-versus-host disease (GVHD) and graft rejection, 2) intestinal inflammation and its modification in IBD and cancer, 3) microbiome-neuron-immunity interplay in mental and physical health, and 4) microbiome-micronutrient-immune interactions during homeostasis and infectious diseases. At this VA field-based meeting, we proposed to explore a multi-disciplinary, multi-institutional, collaborative strategy to initiate a roadmap, specifically focusing on host microbiome-immune interactions among those with service-related chronic diseases to potentially identify novel and translatable therapeutic targets.

Antigen-driven colonic inflammation is associated with development of dysplasia in primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is an immune-mediated disease of the bile ducts that co-occurs with inflammatory bowel disease (IBD) in almost 90% of cases. Colorectal cancer is a major complication of patients with PSC and IBD, and these patients are at a much greater risk compared to patients with IBD without concomitant PSC. Combining flow cytometry, bulk and single-cell transcriptomics, and T and B cell receptor repertoire analysis of right colon tissue from 65 patients with PSC, 108 patients with IBD and 48 healthy individuals we identified a unique adaptive inflammatory transcriptional signature associated with greater risk and shorter time to dysplasia in patients with PSC. This inflammatory signature is characterized by antigen-driven interleukin-17A (IL-17A)+ forkhead box P3 (FOXP3)+ CD4 T cells that express a pathogenic IL-17 signature, as well as an expansion of IgG-secreting plasma cells. These results suggest that the mechanisms that drive the emergence of dysplasia in PSC and IBD are distinct and provide molecular insights that could guide prevention of colorectal cancer in individuals with PSC.

COVID-19 and transtympanic injections for sudden sensorineural hearing loss

BACKGROUND

Multiple reports have linked COVID-19 infection with sudden sensorineural hearing loss (SSNHL), although other studies have failed to demonstrate this association. The current study was conceived to examine the rates of SSNHL across a large, principally national, population by characterizing the rate of transtympanic injections for SSNHL during the pandemic.

METHODS

Retrospective review of all patients that underwent transtympanic injection from 2019 to 2020.

RESULTS

Covering a unique beneficiary population of 9.6 million individuals of all ages in the United States, a statistically significant decrease in transtympanic injections for SSNHL was performed from 2019 to 2020 (p = 0.04, IRR = 0.91, 95 % CI = 0.84-0.99). No patient receiving a transtympanic injection also had a COVID-19 diagnosis.

CONCLUSIONS

These findings support the idea that COVID-19 infections do not clinically significantly increase patients' risk of developing SSNHL. In fact, the decreased exposure through social isolation to other common viruses implicated in causing SSNHL may have actually led to a lower rate of SSNHL during the pandemic.

PIR-B Regulates CD4+ IL17a+ T-Cell Survival and Restricts T-Cell-Dependent Intestinal Inflammatory Responses

BACKGROUND & AIMS

CD4⁺ T cells are regulated by activating and inhibitory cues, and dysregulation of these proper regulatory inputs predisposes these cells to aberrant inflammation and exacerbation of disease. We investigated the role of the inhibitory receptor paired immunoglobulin-like receptor B (PIR-B) in the regulation of the CD4⁺ T-cell inflammatory response and exacerbation of the colitic phenotype.

METHODS

We used Il10^-/- spontaneous and CD4⁺CD45RB^hi T-cell transfer models of colitis with PIR-B-deficient (Pirb^-/-) mice. Flow cytometry, Western blot, and RNA sequencing analysis was performed on wild-type and Pirb^-/- CD4⁺ T cells. In silico analyses were performed on RNA sequencing data set of ileal biopsy samples from pediatric CD and non-inflammatory bowel disease patients and sorted human memory CD4⁺ T cells.

RESULTS

We identified PIR-B expression on memory CD4⁺ interleukin (IL)17a⁺ cells. We show that PIR-B regulates CD4⁺ T-helper 17 cell (Th17)-dependent chronic intestinal inflammatory responses and the development of colitis. Mechanistically, we show that the PIR-B- Src-homology region 2 domain-containing phosphatase-1/2 axis tempers mammalian target of rapamycin complex 1 signaling and mammalian target of rapamycin complex 1-dependent caspase-3/7 apoptosis, resulting in CD4⁺ IL17a⁺ cell survival. In silico analyses showed enrichment of transcriptional signatures for Th17 cells (RORC, RORA, and IL17A) and tissue resident memory (HOBIT, IL7R, and BLIMP1) networks in PIR-B⁺ murine CD4⁺ T cells and human CD4⁺ T cells that express the human homologue leukocyte immunoglobulin-like receptor subfamily B member 3 (LILRB3). High levels of LILRB3 expression were associated strongly with mucosal injury and a proinflammatory Th17 signature, and this signature was restricted to a treatment-naïve, severe pediatric CD population.

CONCLUSIONS

Our findings show an intrinsic role for PIR-B/LILRB3 in the regulation of CD4⁺ IL17a⁺ T-cell pathogenic memory responses.

Maternal EGF limits bacterial translocation in the offspring: a model of enterally acquired Late Onset Sepsis

Late-onset neonatal sepsis (LOS), an important cause of morbidity and mortality in prematurely born infants, results from a bloodstream infection by bacteria of gut origin. It remains unclear how such bacteria translocate from the intestine, though it has been repeatedly observed that breastfed infants, particularly those fed mother’s own milk (MOM), have reduced risk of LOS compared to formula fed infants. Epidermal growth factor (EGF) promotes intestinal barrier function in infants and is present at high concentrations in breast milk post-partum and decreases throughout lactation. We found reduced concentrations of EGF in the stool of premature formula-fed infants compared to MOM-fed infants, and observed a similar decrease in EGF concentrations of stool of neonatal mice asynchronously cross-fostered (ACF) to dams that had delivered two weeks prior. LOS bloodstream isolates of E. coli colonized the tracts of all pups but translocated and disseminated systemically only in ACF mice resulting in bacteremia and rapid death. Oral gavage of recombinant EGF reduced bacteria translocation and prevented the development of systemic disease in ACF mice. Thus, disruption of maternally delivered EGF in ACF mice results in translocation of pathogens from the gut, and a sepsis-like disease. In conclusion we have identified a mechanism whereby gut-residing pathogens gain systemic access and have developed a novel animal model replicating this mechanism to explore the protective effect of breastmilk and EGF in LOS.

Altered selection during language processing in individuals at high risk for psychosis

INTRODUCTION

Performance in the executive function (EF) domain has been linked to symptoms and functional outcomes in psychosis. Studies have found that UHR populations have difficulty with verbal fluency, which involves multiple facets of EF. Two potentially implicated EF facets were examined to explore whether these could be dissociated in UHR populations: selection among alternatives (measured by selection costs) and retrieval from semantic memory retrieval (measured by retrieval costs).

METHODS

A total of 45 UHR individuals and 46 healthy controls (HVs) were assessed with a verb generation task. Differences in selection cost (RT difference between high and low selection demand conditions) and retrieval cost (RT difference between high and low retrieval demand conditions) were examined and participants were also assessed for clinical symptoms.

RESULTS

The UHR group showed greater selection costs relative to HVs, F (1, 91) = 4.39, p = 0.039. However, there were no group differences on retrieval cost, F (1, 91) = 0.63, p = 0.43. A positive association (r = 0.41) was found between disorganized and negative symptoms and selection costs (but not retrieval costs) in the UHR group. There was no significant association between selection costs and positive symptoms.

DISCUSSION

Increased selection costs may reflect impaired performance in the neural inhibition domain of EF in the UHR population, potentially underlying a mechanistically distinct EF subdomain that affects the group's ability to efficiently select between competing options. Findings suggest that UHR individuals may exhibit impairment in selecting among alternatives, but not in retrieval from semantic memory.

Impaired granulocyte-macrophage colony-stimulating factor bioactivity accelerates surgical recurrence in ileal Crohn’s disease

AIM

To examine the relationship between elevated granulocyte-macrophage colony-stimulating factor (GM-CSF) auto-antibodies (Ab) level and time to surgical recurrence after initial surgery for Crohn’s disease (CD).

METHODS

We reviewed 412 charts from a clinical database at tertiary academic hospital. Patients included in the study had ileal or ileocolonic CD and surgical resection of small bowel or ileocecal region for management of disease. Serum samples were analyzed for serological assays including GM-CSF cytokine, GM-CSF Ab, ASCA IgG and IgA, and genetic markers including SNPs rs2066843, rs2066844, rs2066845, rs2076756 and rs2066847 in NOD2, rs2241880 in ATG16L1, and rs13361189 in IRGM. Cox proportional-hazards models were used to assess the predictors of surgical recurrence.

RESULTS

Ninety six percent of patients underwent initial ileocecal resection (ICR) or ileal resection (IR) and subsequently 40% of patients required a second ICR/IR for CD. GM-CSF Ab level was elevated at a median of 3.81 mcg/mL. Factors predicting faster time to a second surgery included elevated GM-CSF Ab [hazard ratio (HR) 3.52, 95%CI: 1.45-8.53, P = 0.005] and elevated GM-CSF cytokine (HR = 2.48, 95%CI: 1.31-4.70, P = 0.005). Factors predicting longer duration between first and second surgery included use of Immunomodulators (HR = 0.49, 95%CI: 0.31-0.77, P = 0.002), the interaction effect of low GM-CSF Ab levels and smoking (HR = 0.60, 95%CI: 0.45-0.81, P = 0.001) and the interaction effect of low GM-CSF cytokine levels and ATG16L1 (HR = 0.65, 95%CI: 0.49-0.88, P = 0.006).

CONCLUSION

GM-CSF bioavailability plays a critical role in maintaining intestinal homeostasis. Decreased bioavailability coupled with the genetic risk markers and/or smoking results in aggressive CD behavior.

Microgeographic Proteomic Networks of the Human Colonic Mucosa and Their Association With Inflammatory Bowel Disease

BACKGROUND & AIMS

Interactions between mucosal cell types, environmental stressors, and intestinal microbiota contribute to pathogenesis in inflammatory bowel disease (IBD). Here, we applied metaproteomics of the mucosal-luminal interface to study the disease-related biology of the human colonic mucosa.

METHODS

We recruited a discovery cohort of 51 IBD and non-IBD subjects endoscopically sampled by mucosal lavage at 6 colonic regions, and a validation cohort of 38 no-IBD subjects. Metaproteome data sets were produced for each sample and analyzed for association with colonic site and disease state using a suite of bioinformatic approaches. Localization of select proteins was determined by immunoblot analysis and immunohistochemistry of human endoscopic biopsy samples.

RESULTS

Co-occurrence analysis of the discovery cohort metaproteome showed that proteins at the mucosal surface clustered into modules with evidence of differential functional specialization (eg, iron regulation, microbial defense) and cellular origin (eg, epithelial or hemopoietic). These modules, validated in an independent cohort, were differentially associated spatially along the gastrointestinal tract, and 7 modules were associated selectively with non-IBD, ulcerative colitis, and/or Crohn's disease states. In addition, the detailed composition of certain modules was altered in disease vs healthy states. We confirmed the predicted spatial and disease-associated localization of 28 proteins representing 4 different disease-related modules by immunoblot and immunohistochemistry visualization, with evidence for their distribution as millimeter-scale microgeographic mosaic.

CONCLUSIONS

These findings suggest that the mucosal surface is a microgeographic mosaic of functional networks reflecting the local mucosal ecology, whose compositional differences in disease and healthy samples may provide a unique readout of physiologic and pathologic mucosal states.

Disruption of the gut microbiota by antibiotics exposure during early life promotes spontaneous Th2 responses and loss of tolerance to dietary antigens

Allergic disorders, manifest by T helper 2 (Th2) type immune responses to environmental antigens, are rapidly increasing in children. Regulatory T cells (Tregs) limit Th2 responses, and Treg deficiencies are seen in children with allergic disorders, implying that Treg deficiencies or dysfunction underlie the pathogenesis of Th2 mediated disease. What incurs Treg deficiency and its relationship to the increasing incidence of allergy is unknown, however, studies have shown that the intestinal microbiota plays an important role in regulating Treg differentiation during early life. With this in mind we explored whether oral exposure to specific antibiotics in early life altered Treg populations and predisposed to Th2 responses. We found that exposure of mice to a combination of broad spectrum oral antibiotics between days 10 and 20 of life abrogated tolerance to a dietary antigen, ovalbumin (Ova). Exposure of mice to single antibiotics of varying spectra between days 10 and 20 of life had a range of effects from abrogation of oral tolerance to the spontaneous development of Th2 responses manifested by increased levels of IL-13 in the serum in the absence of challenge. Ongoing studies are evaluating the effect of the respective antibiotic regimens on the intestinal microbial community using 16S bacterial DNA sequencing, with the aim to link alterations in the microbial composition to the immunological profile of the respective treatment groups. In summary, our results show that disruption of the intestinal microbiota by exposure to specific antibiotics during a period in early life results in loss of Tregs, promotes Th2 immunity, and impair establishment of oral tolerance to dietary antigen.

CCR6 expression by small intestine lamina propria dendritic cells is critical for surveillance of the luminal contents at the villous epithelial surface (CCR5P.251)

The immune system underlying the villous epithelium is continually monitoring its complex environment to appropriately respond with the induction of tolerance or immunity. However little is known about the factors promoting immune surveillance of the luminal contents at this surface. Mice deficient in lymphotoxin beta receptor (LTBR) have a decreased population of dendritic cells (DCs) associated with the villous epithelium. The chemokine CCL20 is expressed by the villous epithelium in a LTBR dependent manner, and CCR6, the only receptor for CCL20, is expressed by the LP-DCs associating with the villous epithelium. Using an in vivo imaging approach, we observed that LP-DC from CCR6 deficient mice were further from the intestinal lumen and flow cytometric analysis revealed they had a decreased population of epithelia associated LP-DCs. Mixed bone marrow transfers confirmed that CCR6 expression by DCs was required for association with the epithelium. In vivo imaging and flow cytometry revealed that LP-DCs from CCR6-/- mice were not impaired at migrating in the lymphatics or populating the mesenteric lymph node. However LP-DCs from CCR6-/- mice were deficient at acquiring epithelial cell proteins and intraluminal ovalbumin, and were deficient in priming immune responses to luminal antigen in the mesenteric lymph nodes. These findings identify an essential role for CCR6 expression by LP-DCs in surveillance of the luminal environment at the villous epithelial surface.

Goblet cell-associated antigen passages are reduced during enteric infection (MUC4P.831)

The intestinal mucosa is continually exposed to foreign antigens derived from the diet, commensal bacteria, and pathogens. Regulating the exposure of the immune system to this broad array of antigens is crucial to ensure intestinal homeostasis and to respond appropriately to enteric infections. Using in vivo two-photon imaging of the intestine of live mice, we recently demonstrated that under steady state conditions a subset of small intestinal goblet cells (GCs) transport luminal antigens to CD103+ dendritic cells (DCs) by forming goblet cell-associated antigen passages (GAPs). To understand how enteric infection altered GCs and GAPs, we infected mice with wildtype fluorescently labeled Salmonella typhimurium and evaluated GCs and GAPs using fluorescence microscopy. Within hours of intraluminal exposure, Salmonella preferentially localized around and within GCs that had formed GAPs. 24 hours after oral Salmonella infection, a subset of GCs were found to be apoptotic, and 72 hours after infection, GAPs were significantly decreased beyond the level of GC apoptosis. Salmonella infection resulted in epithelial activation of the epidermal growth factor receptor (EGFR), a potential regulator of GC secretion and GAP formation. These observations indicate that GAPs may provide a portal of entry for pathogens, and that GAP formation is reduced following enteric infection potentially to avoid delivery of luminal antigen to lamina propria immune cells in a hostile environment.

Colonic goblet cell intrinsic, Myd88 dependent, microbial sensing rapidly regulates antigen delivery to the lamina propria immune system (MUC4P.853)

The delivery of antigens across the intestinal epithelium is an early and critical event in homeostatic responses to innocuous antigens and inflammatory responses to potential pathogens. The factors and mechanisms regulating antigen delivery to the lamina propria (LP) immune system are largely unknown. We recently demonstrated when small intestinal goblet cells (GCs) secrete, they form goblet cell-associated antigen passages (GAPs) and deliver luminal antigens to LP dendritic cells (DCs). Here we report in the basal state, GAP formation is driven by acetylcholine (Ach) signaling via the muscarinic ACh receptor 4 (mAChR4) expressed by GCs. In contrast to conventionally housed mice, GAPs were present in the colon of mice with a reduced microbiota or altered microbial sensing. Formation of colonic GAPs in these mice was dependent upon mAChR4 signaling. Moreover, in mice with a reduced microbial load, luminal microbial stimuli inhibited GAP formation within minutes. In vitro studies revealed GC intrinsic sensing of the microbiota rapidly inhibited ACh induced GC secretion, and conditional deletion of Myd88 in GCs in conventionally housed mice resulted in the spontaneous formation of colonic GAPs, and the delivery of luminal antigen to colonic LP DCs. These findings identify a role for microbial sensing by colonic GCs to rapidly regulate antigen delivery to the LP immune system, and preventing delivery of luminal antigens when the luminal microbial load is abundant and complex.

Enteric antigens are delivered to the infant colonic immune system to promote enhance and long-lasting tolerance (MUC8P.801)

Epidemiological studies indicate early exposure to microbial and dietary antigens via the gastrointestinal (GI) tract is associated with a decreased susceptibility for food allergy and inflammatory bowel disease later in life. However, the properties of the infant GI tract conferring this benefit are largely unknown. We found introduction of a dietary antigen during infancy, as opposed to early adulthood, promoted enhanced and lasting tolerance. Using in vivo imaging and ex vivo analysis of lamina propria antigen presenting cells following intraluminal antigen administration, we observed, in contrast to adults, enteric antigens were delivered to the colonic immune system in infants, which had an increased tolerogenic capacity. Antigen delivery to the infant colon immune system was mediated by goblet cell-associated antigen passages (GAPs) and the formation of colonic GAPs was regulated by goblet cell intrinsic sensing of the luminal microbiota, which inhibited antigen delivery and GAP formation in the colon as the microbiota expanded after weaning. Additionally, inhibition of colonic GAPs during enteric antigen exposure during infancy abrogated the tolerance induction. We propose antigen delivery to the infant colon allows the immune system to become ‘educated’ to dietary and microbial antigens, preventing responses to innocuous antigens encountered in the adult colon where the environment contains abundant and complex microbial stimuli.

Toll-like receptor signaling regulates mucosal barrier function and antigen acquisition in the small intestine (P3266)

The mucosal immune system must efficiently recognize foreign antigen during intestinal infection and yet avoid triggering inappropriate inflammatory responses to commensal microbes and food antigens. In vivo two-photon imaging revealed that low-molecular weight material can cross the epithelium of the small intestine during goblet cell secretion, a phenomenon termed goblet cell-associated antigen passages (GAPs). GAPs are abundant in the steady-state and selectively deliver foreign antigen to CD103+ lamina propria dendritic cells with tolerogenic potential. However, under pathological conditions, goblet cell secretion and epithelial permeability are dramatically altered. The cellular mechanisms that regulate barrier function in response to luminal microbial products are poorly understood, but have important ramifications for intestinal pathogenesis and oral vaccine efficacy. We found that Toll-like receptor (TLR) ligands introduced acutely into the intestines of germ free mice modulated GAP formation in vivo. Furthermore, mice deficient in TLRs that signal through TRIF, lacked GAPs and had reduced epithelial permeability. We propose that a subset of villus epithelial cells expressing TLR3/TLR4 and containing high levels of serotonin (5HT) can induce GAP formation in the small intestine by secreting 5HT in response to TLR ligands.

Luminal microbial sensing regulates colonic goblet cell associated antigen passages through the activation of p42/p44 MAPK and the EGFR (P3154)

The intestinal tract is full of proteins ranging in antigenicity from inert food antigens to potential pathogens and bacterial toxins. A major focus of mucosal immunology is to better understand how these antigens are acquired and introduced to the immune system. Using intravital two-photon imaging we recently showed that in conventionally housed mice, small intestinal goblet cells, but not colonic goblet cells, act as a route of antigen delivery to intestinal dendritic cells by forming goblet cell-associated antigen passages (GAPs), in a mechanism linked to goblet cell secretion. In contrast to conventionally housed mice, we observed that GAPs were present in the colon of germfree mice, mice given antibiotics, and, surprisingly, neonatal mice. We found that the activation of p44/p42 MAPK and EGFR in colonic goblet cells correlated with the presence of luminal microbiota and the ability to sense the flora via TLRs. Inhibition of either p42/p44 MAPK or EGFR allowed GAP formation to occur in the colon of SPF housed mice, and colonic GAPs in germfree mice were blocked by activation of the EGFR. These observations indicate that sensing the enteric flora inhibits colonic GAP formation. This regulation of antigen delivery would allow sampling of luminal antigens when the environment is permissive, such as in the homeostatic small intestine, but would prevent sampling luminal antigens in a hostile environment, such as the high microbial load in the colon or during infection.

Goblet cells deliver luminal retinoids and imprint CD103+ lamina propria dendritic cells (P3223)

The intestinal lamina propria (LP) underlies the villous epithelia and contains a large population of CD103+ myeloid DCs. CD103+ LP-DCs generate the vitamin A metabolite all-trans retinoic acid (ATRA) and promote intestinal type responses including generating Foxp3+ T regulatory cells, imprinting gut homing expression on lymphocytes, and facilitating IgA production. In vivo studies demonstrated that luminal retinoids from the diet or bile are required to condition intestinal LP-DCs to generate ATRA. How luminal retinoids confer this capacity is not known. Goblet cell associated antigen passages (GAPs) provides a portal for CD103+ LP-DCs to acquire soluble luminal substances and goblet cell (GCs) proteins, suggesting a role for GCs and GAPs in imprinting CD103+ LP-DCs. Using an in vivo two-photon (2P) imaging approach, we found that GAPs delivered luminal retinoids and the enzyme required to metabolize pro-vitamin A to LP-DCs. In the absence of GCs, LP-DCs are not imprinted with ALDH activity. We observed that LP-DCs express CCR6, which was required for LP-DCs to associate with the small intestine epithelium. CCR6 deficient LP-DCs do not acquire GC proteins or luminal antigens, do not become imprinted with ALDH activity, and are impaired at inducing ATRA dependent events. These findings demonstrate that GAPs deliver luminal retinoids and the enzymes required to metabolize these retinoids to CD103+ LP-DCs, and accordingly play a critical role in imprinting CD103+ LP-DCs.

Stromal cells participate in the murine esophageal mucosal injury response

We identified α-smooth muscle actin (α-SMA)- and vimentin-expressing spindle-shaped esophageal mesenchymal cells in the adult and neonate murine esophageal lamina propria. We hypothesized that these esophageal mesenchymal cells express and secrete signaling and inflammatory mediators in response to injury. We established primary cultures of esophageal mesenchymal cells using mechanical and enzymatic digestion. We demonstrate that these primary cultures are nonhematopoietic, nonendothelial, stromal cells with myofibroblast-like features. These cells increase secretion of IL-6 in response to treatment with acidified media and IL-1β. They also increase bone morphogenetic protein (Bmp)-4 secretion in response to sonic hedgehog. The location of these cells and their biological functions demonstrate their potential role in regulating esophageal epithelial responses to injury and repair.

Stromal cells participate in the murine esophageal mucosal injury response

We identified α-smooth muscle actin (α-SMA)- and vimentin-expressing spindle-shaped esophageal mesenchymal cells in the adult and neonate murine esophageal lamina propria. We hypothesized that these esophageal mesenchymal cells express and secrete signaling and inflammatory mediators in response to injury. We established primary cultures of esophageal mesenchymal cells using mechanical and enzymatic digestion. We demonstrate that these primary cultures are nonhematopoietic, nonendothelial, stromal cells with myofibroblast-like features. These cells increase secretion of IL-6 in response to treatment with acidified media and IL-1β. They also increase bone morphogenetic protein (Bmp)-4 secretion in response to sonic hedgehog. The location of these cells and their biological functions demonstrate their potential role in regulating esophageal epithelial responses to injury and repair.

Imprinting CD103+ LP-DCs and the acquisition of luminal antigen is dependent upon CCR6 (71.12)

Dendritic cells (DCs) play a crucial role initiating and guiding immune responses. DCs are found within the gut associated lymphoid tissue, within the lamina propria (LP), and closely associated with the small intestinal epithelium. The epithelia associated DCs (EADC) are positioned to be imprinted by epithelial cells and to acquire luminal antigens, however the factors recruiting LPDCs to the epithelium are not known. We observed that CCL20 is expressed by small intestine villous enterocytes, and that the receptor for CCL20, CCR6, is expressed by small intestine EADCs and LPDCs. CCR6-/- mice had a diminished population of EADCs, but not LPDCs when compared with wildtype mice. Mixed bone marrow chimeric mice revealed that CCR6-/- LPDCs were less efficient at associating with the epithelium, demonstrating a requirement for CCR6 recruiting EADCs. Consistent with our observation that goblet cells (GC) act as passages delivering luminal antigens and GC antigens, LPDCs from CCR6-/- mice were inefficient at presenting luminal antigens to T-cells and rarely stained positive for the goblet cell protein cytokeratin 18. Moreover CD103+ LPDCs from CCR6-/- mice had decreased aldehyde dehydrogenase activity, consistent with the requirement for DC-epithelia associations to imprint DCs with a mucosal phenotype. These observations demonstrate an essential role for CCR6 in recruiting LPDCs to the epithelium where these DCs are imprinted and acquire luminal and GC antigens.

Goblet cell-associated antigen passages and luminal antigen delivery to intestinal dendritic cells (71.6)

Understanding how pathogen-specific immunity is elicited in the gut against the overwhelming background of foreign antigens from food and normal flora is essential for treating intestinal infections and inflammatory diseases. Oral tolerance is mediated in part by intestinal dendritic cells (DCs) that promote the development of regulatory T cells. Beneath the villous epithelium, the lamina propria (LP) contains a large population of DCs (CD11c+ CD11b+ MHCII+ cells), CD103+ CX3CR1- DCs, which can promote IgA production, imprint gut homing on lymphocytes, and induce the development of regulatory T cells, and CD103- CX3CR1+ DCs, which can contribute to TNFα production, colitis, and the development of Th17 T cells. How luminal antigens are captured by LP-DCs in the steady-state is controversial. Using a combination of in vivo two-photon imaging and ex vivo analyses we show that goblet cells (GCs) within the small intestine function as passages to deliver low-molecular weight antigens from the intestinal lumen to underlying CD103+ LP-DCs, a phenomenon we have termed goblet-cell associated antigen passages (GAPs). The preferential delivery of antigens to CD103+ LP-DCs has important implications for peripheral tolerance induction at the mucosa. The mechanisms that regulate GAP function during homeostasis and pathogenic infection are the focus of ongoing work.

AHR drives the development of gut ILC22 cells and postnatal lymphoid tissues via pathways dependent on and independent of Notch

Innate lymphoid cells (ILCs) of the ILC22 type protect the intestinal mucosa from infection by secreting interleukin 22 (IL-22). ILC22 cells include NKp46(+) and lymphoid tissue-inducer (LTi)-like subsets that express the aryl hydrocarbon receptor (AHR). Here we found that Ahr(-/-) mice had a considerable deficit in ILC22 cells that resulted in less secretion of IL-22 and inadequate protection against intestinal bacterial infection. Ahr(-/-) mice also lacked postnatally 'imprinted' cryptopatches and isolated lymphoid follicles (ILFs), but not embryonically 'imprinted' Peyer's patches. AHR induced the transcription factor Notch, which was required for NKp46(+) ILCs, whereas LTi-like ILCs, cryptopatches and ILFs were partially dependent on Notch signaling. Thus, AHR was essential for ILC22 cells and postnatal intestinal lymphoid tissues. Moreover, ILC22 subsets were heterogeneous in their requirement for Notch and their effect on the generation of intestinal lymphoid tissues.

Epimorphin deletion protects mice from inflammation-induced colon carcinogenesis and alters stem cell niche myofibroblast secretion

Epithelial-mesenchymal interactions regulate normal gut epithelial homeostasis and have a putative role in inflammatory bowel disease and colon cancer pathogenesis. Epimorphin is a mesenchymal and myofibroblast protein with antiproliferative, promorphogenic effects in intestinal epithelium. We previously showed that deletion of epimorphin partially protects mice from acute colitis, associated with an increase in crypt cell proliferation. Here we explored the potential therapeutic utility of modulating epimorphin expression by examining the effects of epimorphin deletion on chronic inflammation-associated colon carcinogenesis using the azoxymethane/dextran sodium sulfate (AOM/DSS) model. We found that mice in which epimorphin expression was absent had a marked reduction in incidence and extent of colonic dysplasia. Furthermore, epimorphin deletion in myofibroblasts altered the morphology and growth of cocultured epithelial cells. Loss of epimorphin affected secretion of soluble mesenchymal regulators of the stem cell niche such as Chordin. Importantly, IL-6 secretion from LPS-treated epimorphin-deficient myofibroblasts was completely inhibited, and stromal IL-6 expression was reduced in vivo. Taken together, these data show that epimorphin deletion inhibits chronic inflammation-associated colon carcinogenesis in mice, likely as a result of increased epithelial repair, decreased myofibroblast IL-6 secretion, and diminished IL-6-induced inflammation. Furthermore, we believe that modulation of epimorphin expression may have therapeutic benefits in appropriate clinical settings.

A small intestine trans-epithelial conduit system assists in lamina propria DC sampling (90.2)

The mechanisms by which lamina propria DCs sample antigens from the gut remains a crucial topic in mucosal immunology. DCs acquire antigen by several distinct processes including M cell transcytosis, specialized transport involving the neonatal Fc receptor, paracellular leak and by DC trans-epithelial dendrite extension. The continuous sampling of luminal contents by gut resident DCs could both contribute to rapid pathogen recognition and provide normal flora and food antigens for tolerance induction. We used two-photon microscopy, to examine DC sampling behavior in vivo and discovered a previously unreported small-intestine-trans-epithelial-conduit (SiTEC) system. We found that SiTECs could carry macromolecules across the epithelium to the lamina propria where they were taken up by resident DCs. SiTECs have a functional molecular weight cut-off of approximately 70kD based on dextran permeability and can pass small proteins as well. The SiTEC system presents a simple mechanism to deliver luminal antigens to lamina propria DCs for the maintenance of tolerance in the steady-state.

Differential role of tumor necrosis factor receptors in TNBS colitis

BACKGROUND

Tumor necrosis factor alpha (TNFalpha) plays a central role in the pathology of T helper 1-mediated colitis such as Crohn's disease; however, the role of its 2 receptors in mediating pathology has not been fully explored.

METHODS

Trinitrobenzene sulfonic acid colitis was used to induce colitis in mice lacking each of the TNF receptors (TNFRs) and in wild-type mice. TNFR1-/- mice lost more weight, became hypothermic, and had increased mortality compared with wild-type C57Bl/6 mice. TNFR2-/- mice, however, lost less weight, had normal temperatures, and had improved survival.

RESULTS

Despite the improved clinical outcomes in TNFR2-/- mice, TNFalpha levels were increased in these mice.

CONCLUSIONS

TNFalpha signaling through TNFR1 is protective in the trinitrobenzene sulfonic acid mouse model of inflammatory bowel disease.

Increased prevalence of celiac disease and need for routine screening among patients with osteoporosis

BACKGROUND

There is an increased prevalence of osteoporosis among patients with celiac disease. However, the relative prevalence of celiac disease among osteoporotic and nonosteoporotic populations is not known, and the benefit of screening the osteoporotic population for celiac disease remains controversial.

METHODS

We evaluated 840 individuals, 266 with and 574 without osteoporosis, from the Washington University Bone Clinic by serologic screening for celiac disease. Individuals with positive serologic test results for antitissue transglutaminase or antiendomysial antibody were offered endoscopic intestinal biopsy to confirm the diagnosis of celiac disease. Individuals with biopsy-proven celiac disease were treated with a gluten-free diet and followed up for improvement in bone mineral density.

RESULTS

Twelve (4.5%) of 266 patients with osteoporosis and 6 (1.0%) of 574 patients without osteoporosis tested positive by serologic screening for celiac disease. All but 2 serologically positive individuals underwent in-testinalbiopsy. Nine osteoporotic patients and 1 nonosteoporotic patient had positive biopsy results. The prevalence of biopsy-proven celiac disease was 3.4% among the osteoporotic population and 0.2% among the nonosteoporotic population. All biopsy-positive individuals tested positive by antitissue transglutaminase and antiendomysial antibody. The antitissue transglutaminase levels correlated with the severity of osteoporosis as measured by T score, demonstrating that the more severe the celiac disease the more severe the resulting osteoporosis. Treatment of the patients with celiac disease with a gluten-free diet resulted in marked improvement in T scores.

CONCLUSIONS

The prevalence of celiac disease among osteoporotic individuals (3.4%) is much higher than that among nonosteoporotic individuals (0.2%). The prevalence of celiac disease in osteoporosis is high enough to justify a recommendation for serologic screening of all patients with osteoporosis for celiac disease.

The lymphotoxin-beta receptor is critical for control of murine Citrobacter rodentium-induced colitis

BACKGROUND AND AIMS

Lymphotoxin is a tumor necrosis factor-family cytokine. Blocking of lymphotoxin alpha 1 beta 2 /lymphotoxin-beta receptor interactions prevents experimental colitis in mice, and this suggests a potential treatment principle of human inflammatory bowel disease. Infection of mice with Citrobacter rodentium serves as an animal model for human infectious colitis induced by enteropathogenic Escherichia coli . We studied the role of lymphotoxin alpha 1 beta 2 /lymphotoxin-beta receptor signaling in Citrobacter rodentium -induced colitis.

METHODS

Mice with disrupted lymphotoxin alpha 1 beta 2 /lymphotoxin-beta receptor interactions secondary to gene defects (lymphotoxin-alpha -/- , lymphotoxin-beta -/- , and lymphotoxin-beta receptor -/- ) or treatment with the antagonist lymphotoxin-beta receptor-immunoglobulin G fusion protein were infected with Citrobacter rodentium . Body weight, fecal excretion of Citrobacter rodentium , and disease-related mortality were monitored. Spleen and liver organ cultures of mice assessed systemic infection. Intestinal inflammation and lymphoid architecture were histologically recorded in the large intestine, mesenteric lymph nodes, and spleen of infected mice.

RESULTS

Inhibition of lymphotoxin alpha 1 beta 2 /lymphotoxin-beta receptor interactions was associated with increased severity of Citrobacter rodentium -induced colitis, as indicated by increased disease-related mortality, more severe weight loss, intestinal bacterial abscesses, and a higher burden of Citrobacter rodentium in the spleen and liver of -/- and lymphotoxin-beta receptor-immunoglobulin G-treated mice. There was a reduction of CD11c + dendritic cells in the spleen of naive and infected -/- and lymphotoxin-beta receptor-immunoglobulin G-treated mice. In infected lymphotoxin-beta receptor -/- mice, anti- Citrobacter rodentium immunoglobulin G2a levels were decreased, whereas immunoglobulin G1 levels were increased. Citrobacter rodentium -induced interleukin-4 secretion was increased in lymphotoxin-beta receptor -/- mice.

CONCLUSIONS

Lymphotoxin alpha 1 beta 2 /lymphotoxin-beta receptor interactions are critical for immunity against Citrobacter rodentium in mice. Impaired anti-enteropathogenic Escherichia coli immunity may be anticipated in anti-lymphotoxin-beta receptor-directed therapy for human inflammatory bowel disease.

Denervation and reinnervation in congenital brachial palsy

Motor unit number estimation (MUNE) was shown to be useful in assessing the neurophysiological status of 18 subjects with congenital brachial palsy. This was especially so since conventional M-wave measurements may give misleading impressions as to the extent of motor axon regeneration. In most subjects the involvement of sensory nerve fibers indicated that the traumatic lesions included postganglionic segments of the fibers, with or without preganglionic damage. In a minority the lesions were purely preganglionic. Digital sensory nerve involvement was more in a mediolateral direction, consistent with greater damage to the uppermost elements in the brachial plexus. In 5 individuals, MUNE and sensory testing showed that there had been trauma to the supposedly unaffected arm. Discrepancies between sensory and motor results suggested that reinnervation of the biceps brachii muscle was greater than that of the intrinsic muscles of the hand. In one subject examined serially, reinnervation of the hand muscles was detected by 10 months and continued in the hypothenar muscles for the next 6 years.

Depression of human electromyographic activity by fatigue of a synergistic muscle

In human volunteers, lateral gastrocnemius muscles were stimulated electrically under ischemic conditions so as to produce fatigue. Recordings of electromyographic (EMG) activity were then made from those muscles and simultaneously from untreated medial gastrocnemius muscles during maximal voluntary efforts. In the lateral gastrocnemius the mean amount of EMG activity declined by 52% and was associated with a 35% reduction in the mean amplitude of the M wave (muscle compound action potential) and an insignificant change in M-wave area. In the medial gastrocnemius the EMG was also diminished, by 29%, but there were no significant changes in M-wave amplitude or area. The findings in the medial gastrocnemius are consistent with the existence of an inhibitory reflex effect which originates in the fatigued lateral gastrocnemius muscle and serves to depress excitation in motoneurons supplying that muscle and also in those innervating synergists. The inhibitory effect appears to be long-lasting, in that a significant reduction of the EMG could still be demonstrated 10 min after release of the arterial cuff.