Background and aimsColonoscopy practice has evolved with a trend towards water-assisted insertion. A recent national survey suggests a hybrid approach to colonic distension during insertion, with water used predominately to the splenic flexure and carbon dioxide (CO2) with water used thereafter to the caecum, is commonly used. This contrasts with the water exchange technique where no CO2is used. This study aimed to evaluate whether a hybrid or water exchange technique allows more efficient colonoscopy.MethodsThis prospective, randomised controlled trial was conducted between March 2021 and June 2022. Participants were randomised 1:1 to hybrid or water exchange colonoscopy, performed by four experienced colonoscopists. The primary outcome was total procedure time with secondary outcomes of caecal intubation time, caecal intubation rate, polyp detection, loop formation, number of ancillary manoeuvres, sedation use and patient comfort.Results256 patients were invited, and 246 were randomised to either hybrid or water exchange colonoscopy. 122 patients were included in each arm of the primary analysis. Total procedure time was greater in the water exchange group compared with hybrid (29 vs 25 min, p=0.009). Patient reposition episodes occurred more frequently in the water exchange group vs hybrid group (5.5 vs 5, p=0.003) and left colon Boston Bowel Preparation Scale (BBPS) score was improved. No difference was seen in all other outcomes.ConclusionA hybrid technique, compared with water exchange, enabled faster colonoscopy without adversely impacting sedation requirement, caecal intubation, overall bowel cleansing and patient comfort. This technique appears to maximise the advantages of both water and CO2to enable more efficient colonoscopy.Trial registration numberNCT04710706.

Background Long-term pouch surveillance outcomes for familial adenomatous polyposis (FAP) are unknown. We aimed to quantify surveillance outcomes and to determine which of selected possible predictive factors are associated with pouch dysplasia.Methods Retrospective analysis of collected data on 249 patients was performed, analyzing potential risk factors for the development of adenomas or advanced lesions (= 10 mm/high grade dysplasia (HGD)/cancer) in the pouch body and cuff using Cox proportional hazards models. Kaplan-Meier analyses included landmark time-point analyses at 10 years after surgery to predict the future risk of advanced lesions.Results Of 249 patients, 76% developed at least one pouch body adenoma, with 16% developing an advanced pouch body lesion; 18% developed an advanced cuff lesion. Kaplan-Meier analysis showed a 10-year lag before most advanced lesions developed; cumulative incidence of 2.8% and 6.4% at 10 years in the pouch body and cuff, respectively. Landmark analysis suggested the presence of adenomas prior to the 10-year point was associated with subsequent development of advanced lesions in the pouch body (hazard ratio [HR] 4.8, 95 %CI 1.6-14.1; P = 0.004) and cuff (HR 6.8, 95% CI 2.5-18.3; P< 0.001). There were two HGD and four cancer cases in the cuff and one pouch body cancer; all cases of cancer/HGD that had prior surveillance were preceded by = 10-mm adenomas.Conclusions Pouch adenoma progression is slow and most advanced lesions occur after 10 years. HGD and cancer were rare events. Pouch phenotype in the first decade is associated with the future risk of developing advanced lesions and may guide personalized surveillance beyond 10 years.

The role of microbiota:immune system dysregulation in the etiology of colorectal cancer (CRC) is poorly understood. CRC develops in gut epithelium, accompanied by low level inflammatory signaling, intestinal microbial dysbiosis and immune dysfunction. We examined populations of intraepithelial lymphocytes in non-affected colonic mucosa of CRC and healthy donors and circulating immune memory to commensal bacterial species and yeasts. γδ T cells and resident memory T cells, populations with a regulatory CD39-expressing phenotype, were found at lower frequencies in the colonic tissue of CRC donors compared to healthy controls. Patterns of T cell proliferative responses to a panel of commensal bacteria were distinct in CRC, while B cell memory responses to several bacteria/yeast were significantly increased, accompanied by increased proportions of effector memory B cells, transitional B cells and plasmablasts in blood. IgA responses to mucosal microbes were unchanged. Our data describe a novel immune signature with similarities to and differences from that of inflammatory bowel disease. They implicate B cell dysregulation as a potential contributor to parainflammation and identify pathways of weakened barrier function and tumor surveillance in CRC-susceptible individuals.

Total colectomy with ileorectal anastomosis (TC-IRA) is a surgical option for patients with familial adenomatous polyposis (FAP). Regular endoscopic surveillance of the rectum is recommended to prevent rectal cancer. We aimed to document polyp progression in the rectum following TC-IRA and evaluate the role of polypectomy during surveillance. Patients with FAP who underwent TC-IRA between 1990 and 2017 were identified. Demographic, endoscopic and genetic data were retrieved. Cumulative rectal adenoma (polyp) counts were obtained, whilst accounting for any polypectomies during the study period. The rate of polyp progression and factors influencing secondary proctectomy were evaluated. One hundred and ninety-nine patients fulfilled our inclusion criteria, of which 44% were male. The median age at colectomy was 19 (range 11–70) years and median preoperative rectal polyp count was 7 (range 0–50). All patients had an APC pathogenic variant, of which 151 (79%) were 5' of the mutation cluster region (MCR), 19 (10%) in the MCR, six (3%) were 3' of the MCR and 15 (8%) had a gross deletion. After a median follow-up of 8.6 (range1–27) years and a median of 11 (range 2–37) flexible sigmoidoscopies per patient, the median rate of polyp progression was 5.5 polyps/year (range 0–70.2). There was no evidence of polyp regression. Eight (4%) patients underwent secondary proctectomy for neoplasia, of which one (0.5%) had rectal adenocarcinoma. A total of 13,527 polyps were removed, a median of 35 polyps/patient (range 0–829). The rate of polyp progression was not significantly associated with genotypic or phenotypic factors. Progression of rectal adenoma burden following TC-IRA appears to be slow and dependent on the length of follow-up. In the modern era of stringent endoscopic surveillance and therapeutic procedures such as cold snare polypectomy, the rate of secondary proctectomy and the risk of rectal cancer after TC-IRA are very low. These findings are important when counselling patients with regard to the choice of surgery for FAP and implementing endoscopic surveillance.

INTRODUCTION: Familial adenomatous polyposis (FAP) is a condition caused by a constitutional pathogenic variant of the adenomatous polyposis coli gene that results in intestinal adenoma formation and colorectal cancer, necessitating pre-emptive colectomy. We sought to examine interaction between the mucosal immune system and commensal bacteria in FAP to test for immune dysfunction that might accelerate tumorigenesis. METHODS: Colonic biopsies were obtained from macroscopically normal mucosal tissue from 14 healthy donors and 13 patients with FAP during endoscopy or from surgical specimens. Intraepithelial and lamina propria lymphocytes were phenotyped. Intraepithelial microbes were labeled with anti-IgA/IgG and analyzed by flow cytometry. RESULTS: Proportions of resident memory CD103-expressing CD8+ and γδ T-cell receptor+ intraepithelial lymphocytes were dramatically reduced in both the left and right colon of patients with FAP compared with healthy controls. In lamina propria, T cells expressed less CD103, and CD4+ CD103+ cells expressed less CD73 ectonucleotidase. IgA coating of epithelia-associated bacteria, IgA+ peripheral B cells, and CD4 T-cell memory responses to commensal bacteria were increased in FAP. DISCUSSION: Loss of resident memory T cells and γδ T cells in mucosal tissue of patients with FAP accompanies intestinal microbial dysbiosis previously reported in this precancerous state and suggests impaired cellular immunity and tumor surveillance. This may lead to barrier dysfunction, possible loss of regulatory T-cell function, and excess IgA antibody secretion. Our data are the first to implicate mucosal immune dysfunction as a contributing factor in this genetically driven disease and identify potentially critical pathways in the etiology of CRC.

Aim Total colectomy with ileorectal anastomosis (TC-IRA) is a surgical option for patients with familial adenomatous polyposis (FAP). Regular endoscopic surveillance of the rectum is recommended to prevent rectal cancer. We aimed to document polyp progression in the rectum following TC-IRA and evaluate the role of polypectomy during surveillance. Method Patients with FAP who underwent TC-IRA between 1990 and 2017 were identified. Demographic, endoscopic and genetic data were retrieved. Cumulative rectal adenoma (polyp) counts were obtained, whilst accounting for any polypectomies during the study period. The rate of polyp progression and factors influencing secondary proctectomy were evaluated. Results One hundred and ninety-nine patients fulfilled our inclusion criteria, of which 44% were male. The median age at colectomy was 19 (range 11-70) years and median preoperative rectal polyp count was 7 (range 0-50). All patients had an APC pathogenic variant, of which 151 (79%) were 5' of the mutation cluster region (MCR), 19 (10%) in the MCR, six (3%) were 3' of the MCR and 15 (8%) had a gross deletion. After a median follow-up of 8.6 (range1-27) years and a median of 11 (range 2-37) flexible sigmoidoscopies per patient, the median rate of polyp progression was 5.5 polyps/year (range 0-70.2). There was no evidence of polyp regression. Eight (4%) patients underwent secondary proctectomy for neoplasia, of which one (0.5%) had rectal adenocarcinoma. A total of 13,527 polyps were removed, a median of 35 polyps/patient (range 0-829). The rate of polyp progression was not significantly associated with genotypic or phenotypic factors. Conclusion Progression of rectal adenoma burden following TC-IRA appears to be slow and dependent on the length of follow-up. In the modern era of stringent endoscopic surveillance and therapeutic procedures such as cold snare polypectomy, the rate of secondary proctectomy and the risk of rectal cancer after TC-IRA are very low. These findings are important when counselling patients with regard to the choice of surgery for FAP and implementing endoscopic surveillance.

Background: Bacteroides thetaiotaomicron (Bt) is a prominent member of the human intestinal microbiota that, like all Gram-negative bacteria, naturally generates nanosized outer membrane vesicles (OMVs) which bud off from the cell surface. Importantly, OMVs can cross the intestinal epithelial barrier to mediate microbe-host cell crosstalk involving both epithelial and immune cells to help maintain intestinal homeostasis. Here we have examined the interaction between Bt OMVs and blood or colonic mucosa-derived dendritic cells (DC) from healthy individuals and patients with Crohn’s disease (CD) or ulcerative colitis (UC). Results: In healthy individuals, Bt OMVs stimulated significant (p<0.05) IL-10 expression by colonic DC, whereas in peripheral blood-derived DC they also stimulated significant (p<0.001 and p<0.01, respectively) expression of IL-6 and the activation marker CD80. Conversely, in UC Bt OMVs were unable to elicit IL-10 expression by colonic DC. There were also reduced numbers of CD103+ DC in the colon of both UC and CD patients compared to controls, supporting a loss of regulatory DC in both diseases. Furthermore, in CD and UC, Bt OMVs elicited a significantly lower proportion of DC which expressed IL-10 (p<0.01 and p<0.001, respectively) in blood compared to controls. These alterations in DC responses to Bt OMVs were seen in patients with inactive disease, and thus are indicative of intrinsic defects in immune responses to this commensal in inflammatory bowel disease (IBD). Conclusions: Overall, our findings suggest a key role for OMVs generated by the commensal gut bacterium Bt in directing a balanced immune response to constituents of the microbiota locally and systemically during health which is altered in IBD patients.

Background and Aims The intestinal microbiota is closely associated with resident memory lymphocytes in mucosal tissue. We sought to understand how acquired cellular and humoral immunity to the microbiota differ in health versus inflammatory bowel disease [IBD]. Methods Resident memory T cells [Trm] in colonic biopsies and local antibody responses to intraepithelial microbes were analysed. Systemic antigen-specific immune T and B cell memory to a panel of commensal microbes was assessed. Results Systemically, healthy blood showed CD4 and occasional CD8 memory T cell responses to selected intestinal bacteria, but few memory B cell responses. In IBD, CD8 memory T cell responses decreased although B cell responses and circulating plasmablasts increased. Possibly secondary to loss of systemic CD8 T cell responses in IBD, dramatically reduced numbers of mucosal CD8+ Trm and γδ T cells were observed. IgA responses to intraepithelial bacteria were increased. Colonic Trm expressed CD39 and CD73 ectonucleotidases, characteristic of regulatory T cells. Cytokines/factors required for Trm differentiation were identified, and in vitro-generated Trm expressed regulatory T cell function via CD39. Cognate interaction between T cells and dendritic cells induced T-bet expression in dendritic cells, a key mechanism in regulating cell-mediated mucosal responses. Conclusions A previously unrecognised imbalance exists between cellular and humoral immunity to the microbiota in IBD, with loss of mucosal T cell-mediated barrier immunity and uncontrolled antibody responses. Regulatory function of Trm may explain their association with intestinal health. Promoting Trm and their interaction with dendritic cells, rather than immunosuppression, may reinforce tissue immunity, improve barrier function, and prevent B cell dysfunction in microbiota-associated disease and IBD aetiology.

44 Background & Aims: The intestinal microbiota is closely associated with resident memory 45 lymphocytes in mucosal tissue. We sought to understand how acquired cellular and humoral 46 immunity to the microbiota differ in health versus inflammatory bowel disease (IBD). 47 Methods: Resident memory T-cells (Trm) in colonic biopsies and local antibody responses to 48 intraepithelial microbes were analyzed. Systemic antigen-specific immune Tand B-cell 49 memory to a panel of commensal microbes was assessed. 50 Results: Systemically, healthy blood showed CD4 and occasional CD8 memory T-cell 51 responses to selected intestinal bacteria but few memory B-cell responses. In IBD, CD8 52 memory T-cell responses decreased although B-cell responses and circulating plasmablasts 53 increased. Possibly secondary to loss of systemic CD8 T-cell responses in IBD, dramatically 54 reduced numbers of mucosal CD8 Trm and γδ T-cells were observed. IgA responses to 55 intraepithelial bacteria were increased. Colonic Trm expressed CD39 and CD73 56 ectonucleotidases, characteristic of regulatory T-cells. Cytokines/factors required for Trm 57 differentiation were identified, and in vitro-generated Trm expressed regulatory T-cell 58 function via CD39. Cognate interaction between T-cells and dendritic cells induced T-bet 59 expression in dendritic cells, a key mechanism in regulating cell-mediated mucosal 60 responses. 61 Conclusions: A previously unrecognized imbalance exists between cellular and humoral 62 immunity to the microbiota in IBD, with loss of mucosal T-cell-mediated barrier immunity 63 and uncontrolled antibody responses. Regulatory function of Trm may explain their 64 association with intestinal health. Promoting Trm and their interaction with dendritic cells 65

There is limited experience of endoscopic submucosal dissection (ESD) for resection of colorectal lesions in the West and outcome data tends to be worse than that reported from Japanese centres. We report the outcomes of ESD in a single, tertiary UK referral centre. A prospective database was analyzed including 129 consecutive patients (mean age: 66.6±12.6 years, 62.6% males) with 131 colorectal neoplasms resected by ESD between 3/2012 and 4/2017. Two experienced colonoscopists performed all procedures. The median (IQR) lesion size was 4cm (2-5), 63 (48.1%) lesions were granular-type laterally spreading tumors (LST-G), and 107 (81.7%) were located in the rectum. In 27 (20.6%) cases a flexible endosurgical platform was used to assist ESD of complex rectal polyps [median(IQR) size: 6cm (5-8)] by dynamic trans-anal retraction (Trans-Anal Submucosal Endoscopic Resection; TASER). Histology showed low-grade adenoma/dysplasia in 69 (52.7%), high-grade adenoma/dysplasia in 38 (29%), T1 cancer (<1000μm) in 15 (11.4%), and T1 cancer (≥1000μm) in 9 (6.9%) lesions. The en bloc, histological complete and curative (R0) resection rates were 98.5%, 84.7% and 80.9% respectively. Two (1.6%) cases of delayed bleeding occurred, without transfusion/re-intervention requirement. Perforation occurred in 2 (1.6%) cases: one was recognized and treated intraoperatively with endoclips; the other one was followed up and managed conservatively. Forty-eight (36.6%) patients were electively admitted to hospital post procedure, for a median duration of 1 day (range 1-5). Thirteen patients (9.2%), at risk of lymph node metastasis, underwent additional radical surgery. Eighty-six (65.6%) ESD cases had endoscopic follow-up data over a median duration of 12.1 months (range 3-51.3). The overall local recurrence rate was 3.1%. This was lower in cases with en bloc compared with piecemeal resection (3.6% vs 50%, p=0.09), in cases with histologic complete compared with histologic incomplete resection (2.6% vs 25%, p=0.04), and in cases with R0 compared with non-R0 resection (2.6% vs 22.2%, p=0.05). After a median follow up of 15.5 months (range: 3-55.8), the overall and disease-specific survival in the study population was 98.5% and 100%, respectively. The current study demonstrates favorable clinical outcomes of selected colorectal ESD in a Western endoscopy setting, comparable to those reported in Asian series. Further studies addressing the cost-effectiveness of ESD and comparing its long-term outcome with endoscopic mucosal resection in the West are needed.

Introduction There is limited experience of endoscopic submucosal dissection (ESD) for resection of colorectal lesions in the West and outcome data tends to be worse than that reported from Japanese centres. We report the outcomes of ESD in a single, tertiary UK referral centre. Methods A prospective database was analysed including 165 consecutive patients (mean age: 64.6±12.6 years, 62.4% males) with 173 colorectal neoplasms resected by ESD between 3/2012 and 12/2017. Two experienced colonoscopists performed all procedures. Results The median (IQR) lesion size was 3.5 cm (2–5), and 140 (80.9%) were located in the rectum. Overall, 49.7% were granular-type laterally spreading tumours (LST), 19.7% were non-granular LST, and 30.6% were polypoid lesions. In 29 (16.7%) cases a flexible endosurgical platform was used to assist ESD of complex rectal polyps [median(IQR) size: 6 cm (5–8)] by dynamic trans-anal retraction (Trans-Anal Submucosal Endoscopic Resection; TASER). Histology showed low-grade adenoma/dysplasia in 83 (47.9%), high-grade adenoma/dysplasia in 52 (30%), T1 cancer (<1000 µm) in 17 (9.8%), and T1 cancer (<1000 µm) in 17 (9.8%) lesions. The en bloc, histological complete and curative (R0) resection rates were 97.7%, 80.3% and 76.3% respectively. Three (1.7%) cases of delayed bleeding occurred, with one case requiring transfusion. Perforation occurred in 2 (1.2%) cases: one was recognised and treated intraoperatively with endoclips; the other one was followed up and managed conservatively. Sixty (34.7%) patients were electively admitted to hospital post procedure, for a median duration of 1 day (range 1–5). Twenty patients (12.1%), at risk of lymph node metastasis, underwent additional radical surgery. Eighty-nine (51.4%) ESD cases had endoscopic follow-up data over a median duration of 12 months (range 3.4–51.3). The local recurrence rate was 4/89 (4.5%); all recurrent cases were managed endoscopically. The recurrence rate was lower in cases with en bloc compared with piecemeal resection (3.4% vs 50%, p=0.08), histologic complete compared with histologic incomplete resection (2.5% vs 22.2%, p=0.05), and R0 compared with non-R0 resection (2.5% vs 20%, p=0.06). After a median follow up of 14.6 months (range: 3–55.8), the overall and disease-specific survival in the study population was 98.8% and 100%, respectively. Conclusions The current study demonstrates favourable clinical outcomes of selected colorectal ESD in a Western endoscopy setting. Further studies addressing the cost-effectiveness of ESD and comparing its long-term outcome with endoscopic mucosal resection in the West are needed.

Background & Aims: Most knowledge about gastrointestinal (GI)-tract dendritic cells (DC) relies on murine studies where CD103+ DC specialize in generating immune tolerance with the functionality of CD11b+/− subsets being unclear. Information about human GI-DC is scarce, especially regarding regional specifications. Here, we characterized human DC properties throughout the human colon. Methods: Paired proximal (right/ascending) and distal (left/descending) human colonic biopsies from 95 healthy subjects were taken; DC were assessed by flow cytometry and microbiota composition assessed by 16S rRNA gene sequencing. Results: Colonic DC identified were myeloid (mDC, CD11c+CD123−) and further divided based on CD103 and SIRPα (human analog of murine CD11b) expression. CD103-SIRPα+ DC were the major population and with CD103+SIRPα+ DC were CD1c+ILT3+CCR2+ (although CCR2 was not expressed on all CD103+SIRPα+ DC). CD103+SIRPα- DC constituted a minor subset that were CD141+ILT3−CCR2−. Proximal colon samples had higher total DC counts and fewer CD103+SIRPα+ cells. Proximal colon DC were more mature than distal DC with higher stimulatory capacity for CD4+CD45RA+ T-cells. However, DC and DC-invoked T-cell expression of mucosal homing markers (β7, CCR9) was lower for proximal DC. CCR2 was expressed on circulating CD1c+, but not CD141+ mDC, and mediated DC recruitment by colonic culture supernatants in transwell assays. Proximal colon DC produced higher levels of cytokines. Mucosal microbiota profiling showed a lower microbiota load in the proximal colon, but with no differences in microbiota composition between compartments. Conclusions: Proximal colonic DC subsets differ from those in distal colon and are more mature. Targeted immunotherapy using DC in T-cell mediated GI tract inflammation may therefore need to reflect this immune compartmentalization. Keywords: CCR2, Dendritic Cells, Distal Colon, Human Gastrointestinal Tract, Proximal Colon, Microbiota

Background: A high prevalence of the adherent-invasive E. coli (AIEC) in the intestinal mucosa of Crohn's disease patients has been shown.We previously showed that upon AIEC infection, autophagy is induced in host cells to restrain AIEC intracellular replication.The mechanism underlying such autophagy induction, however, remains largely unknown.Here, we investigated the role of the GCN2/eIF2α/ ATF4 pathway in autophagy response to AIEC infection.Methods: Autophagic activity was assessed by Western blot and immunofluorescent labelling of LC3.Intracellular bacterial number was determined by bacterial invasion assay and confocal microscopy.Binding of ATF4 to autophagy gene promoters was assessed by Chromatin immunoprecipitation (ChIP) assay.Wild type (WT) and GCN2 knockout (KO) mice were infected with an AIEC reference strain LF82 by gavage.Results: Infection of human intestinal epithelial T84 cells with the AIEC LF82 strain activated the GCN2/eIF2α/ATF4 pathway as shown by increased phospho-GCN2 and phospho-eIF2α levels, enhanced ATF4 protein expression, and upregulated mRNA expression levels of ATF4 target genes.To explore the role of this pathway in host responses to AIEC infection, we used GCN2-deficient mouse embryonic fibroblasts (GCN2-/-MEF).GCN2 depletion suppressed eIF2α activation and inhibited the increase in ATF4 protein level induced by LF82 infection.mRNA expression levels of the autophagy genes p62, MAP1lc3, Beclin1, atg3 and atg7 were significantly increased in WT MEF upon LF82 infection, and this was blocked in GCN2-/-MEF.ChIP assay showed that GCN2 depletion inhibited the LF82-induced binding of ATF4 to the promoters of these autophagy genes.Consequently, autophagy induction upon LF82 infection was suppressed in GCN2-/-MEF, leading to increased LF82 intracellular replication and elevated pro-inflammatory cytokine production, compared to WT MEF.In vivo study consistently showed that LF82 infection activated the GCN2/eIF2α/ATF4 pathway in enterocytes from WT mice, but not GCN2 KO mice.In response to AIEC infection, autophagy was induced in WT mouse-derived enterocytes, and this was not observed in KO mice.LF82 persistence in the gut was increased in KO mice, leading to aggravated intestinal inflammation, compared to that in WT mice.Depletion of GCN2 did not affect susceptibility of mice to DSS-induced colitis, indicating that the effects obtained were not a consequence of inflammation and were specific for AIEC infection.Conclusions: The GCN2/eIF2α/ATF4 pathway is activated in host cells during AIEC infection, which is served as a defense mechanism to induce a functional autophagy to control AIEC intracellular replication.

BACKGROUND & AIMS: Most knowledge about gastrointestinal (GO-tract dendritic cells (DC) relies on murine studies where CD103(+) DC specialize in generating immune tolerance with the functionality of CD11B(+/-) subsets being unclear. Information about human GI-DC is scarce, especially regarding regional specifications. Here, we characterized human DC properties throughout the human colon.METHODS: Paired proximal (right/ascending) and distal (left/descending) human colonic biopsies from 95 healthy subjects were taken; DC were assessed by flow cytometry and microbiota composition assessed by 16S rRNA gene sequencing.RESULTS: Colonic DC identified were myeloid (mDC, CD11c(+)CD123(-) ) and further divided based on CD103 and SIRP alpha (human analog of murine CD11b) expression. CD103 SIRP alpha(+) DC were the major population and with CD103(+) SIRP alpha(+) DC were CD1c(+) ILT3(+)CCR2(+) (although CCR2 was not expressed on all CD103(+) SIRP alpha(+) DC). CD103(+)SIRP alpha(-) DC constituted a minor subset that were CD141(+)ILT3(-)CCR2(-). Proximal colon samples had higher total DC counts and fewer CD103(+)SIRP alpha(+) cells. Proximal colon DC were more mature than distal DC with higher stimulatory capacity for CD4(+)CD45RA(+) T-cells. However, DC and DC-invoked T-cell expression of mucosal homing markers (beta 7, CCR9) was lower for proximal DC. CCR2 was expressed on circulating CD1c(+), but not CD141(+) mDC, and mediated DC recruitment by colonic culture supernatants in transwell assays. Proximal colon DC produced higher levels of cytokines. Mucosal microbiota profiling showed a lower microbiota load in the proximal colon, but with no differences in microbiota composition between compartments.CONCLUSIONS: Proximal colonic DC subsets differ from those in distal colon and are more mature. Targeted immunotherapy using DC in T-cell mediated GI tract inflammation may therefore need to reflect this immune compartmentalization.

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)-1β) 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.

ScopeThe human/microbiota cross-talk is partially mediated by bacteria-derived peptides like Serine-Threonine peptide (STp), which is resistant to gut proteolysis, is found in the human healthy colon and induces regulatory properties on gut dendritic cells (DCs); here we characterized human gut DC in ulcerative colitis (UC) patients and studied the effect of STp on their properties.Methods and resultsHuman colonic DC from healthy controls and UC patients were isolated, conditioned for 24 h +/- STp and characterized by flow cytometry, immunohistochemistry, and electron microscopy. Expression of immature DC markers DC-SIGN and ILT3, and Toll-like receptors were increased on gut UC-DC. Langerin (involved in phagocytosis), lymph node homing marker CCR7, and activation markers CD40/CD80/CD86 were decreased in UC. Gut DC had restricted stimulatory capacity for T-cells in UC. Conditioning of DC with STp in vitro reduced Toll-like receptor expression, increased CD40 and CD80 expression, and restored their stimulatory capacity.ConclusionColonic DCs display an abnormal immature phenotype in UC, which was partially restored following STp treatment. Bacteria-derived metabolites, like STp, seem to have a role in gut homeostasis that is missing in UC so they might lead a new era of probiotic products setting the basis for nondrug dietary therapy in inflammatory bowel disease.

Background: There is a gap in the formal assessment of technical skills in polypectomy that is now considered an integral part of colonoscopy. Polypectomy has been shown to reduce the incidence of colorectal cancer but does have associated complications. Polypectomy competency assessment should arguably be a part of the certification process for all endoscopists. A polypectomy competency assessment tool (Direct Observation of Polypectomy Skills [DOPyS]) has been developed and its reliability examined. This study examined the ability of the DOPyS to reliably distinguish between endoscopists with different levels of experience, ie, its construct validity.Objective: To determine the construct validity of the DOPyS.Design: Videos of 32 polypectomies (endoscopic view only) were collected from 2 expert (>1000 colonoscopies) endoscopists (17 polyps) and 6 intermediate-level (100-500 colonoscopies) endoscopists (15 polyps). The videos were edited to include only the entire polypectomy procedure, arranged in random order, and assessed blindly by 4 experienced endoscopists, only 2 of whom were familiar with polypectomy assessment by using the DOPyS before scoring. The differences in overall competency scores (range 1-4; competency, scores >= 3) for the expert and intermediate groups were compared by using the Fisher exact test.Setting: Single center.Results: The analysis suggested that both trained assessors familiar with the DOPyS could reliably distinguish between the expert and intermediate endoscopists (P = .049 and P < .001), with the expert group scoring higher than the intermediate one. For the assessors with no previous experience of the DOPyS, no such difference could be seen (P = .71 and P = .15).Limitations: Small sample and polyp size.Conclusions: The results of the analysis suggested that the DOPyS could reliably differentiate between polypectomies performed by endoscopists of different levels of experience, but only if the assessors were trained in the use of the assessment tool. Training is therefore required to use this tool reliably. (Gastrointest Endosc 2012;75;568-75.)

There is a void in the formal assessment of technical skills in polypectomy which is now considered an integral part of colonoscopy. It has been shown to reduce the incidence of colorectal cancer but does have associated complications. Polypectomy competency assessment should arguably be a part of the certification process for all endoscopists. A polypectomy competency assessment tool (Direct Observation of Polypectomy Skills (DOPyS), which incorporates a 33-point procedure-specific checklist and an overall competency score) has been developed and its reliability, examined. This study examines the ability of the DOPyS to distinguish between endoscopists with different levels of experience (i.e. its construct validity). To determine construct validity of the DOPyS. Thirty-two polypectomy videos (the endoscopic view only) were collected from real patient procedures performed by two experienced (>1000 colonoscopies) endoscopists (17 videos) and six intermediate level (100-500 colonoscopies) endoscopists (15 videos). The videos were edited to include only the entire polypectomy procedure, arranged in random order, and assessed blindly by two experienced endoscopy assessors, both of whom were trained in polypectomy assessment using the DOPyS prior to scoring. The differences in overall competency scores (range 1-4; scores ≥3=competency) for the expert and intermediate groups were compared, and considered significant (p value <0.05) using Fisher's exact test. The results suggest that the DOPyS can determine a difference between endoscopists of different levels of experience, provided the assessors are trained in the use of the assessment tool. Training in assessment is essential to reduce examiner variability and improve reliability of an assessment. Large-scale validation studies are required to strengthen evidence for the use of this tool for routine polypectomy competency assessment.Tabled 1AssessorOverall scoreExpert Group Number of Videos (%)Intermediate Group Number of Videos (%)P-value1Score <32 (12%)7 (47%)0.049Score ≥315 (88%)8 (53%)2Score <31 (6%)12 (80%)<0.001Score ≥316 (94%)3 (20%) Open table in a new tab

Background: Experts are accurate in differentiating small adenomas from hyperplastic polyps at colonoscopy by using narrow-band imaging (NBI).Objective: To prospectively evaluate the effectiveness of an NBI training module on individuals with varying colonoscopy experience.Design: Prospective educational evaluation study.Setting: Academic endoscopy unit.Participants: Twenty-one participants of varying colonoscopy experience (novices, trainees, and experienced gastroenterologists) and 5 experts in NBI.Intervention: Participants completed a computer-based test module consisting of 30 NBI polyp images. No feedback was given. They then completed a computer-based training module on the use of NBI in the differentiation of adenomas and hyperplastic polyps. The test module was then completed a second time.Main Outcome Measurements: Construct validity (the difference in baseline accuracy on the test module between different groups of participants) and content validity (difference in accuracy achieved on the test module before and after training) of the training module.Results: There was a significant difference in the baseline accuracy (P < .001) between experts (0.95; 95% confidence interval [CI], 0.92-0.97), experienced colonoscopists (0.68; 95% CI, 0.68-0.74), trainees (0.75; 95% CI, 0.67-0.82), and novices (0.62; 95% CI, 0.46-0.77). Accuracy increased significantly (P < .001) for all 3 groups after training (novices 0.84; 95% CI, 0.78-0.88, trainees 0.90; 95% Cl, 0.84-0.93, and experienced colonoscopists 0.84; 95% CI, 0.76-0.89). After training, the agreement was moderate at least (kappa = 0.56 for novices, kappa = 0.70 for trainees, and kappa = 0.54 for experienced colonoscopists).Limitations: This study did not assess the accuracy of optical diagnosis in routine clinical practice.Conclusion: A short, computer-based training module can improve the diagnostic accuracy and interobserver agreement for the use of NBI to differentiate adenomas from hyperplastic polyps and could be used for the initial training in optical diagnosis. (Gastrointest Endosc 2011;73:128-33.)