Colonic Eosinophils Research Articles

P016 Reduction of mucosal (active) eosinophils, B cells and T cells after vedolizumab therapy in patients with ulcerative colitis

Abstract Background Patients with ulcerative colitis (UC) are often treated with biological therapies or small molecules. Knowledge about the impact of these therapies on the intestinal and peripheral blood immune cell composition is scarce. Therefore, we investigated how advanced therapies modulate immune cell distribution in UC patients. Methods We included 30 UC patients (53% male, median age 42 years) who started a biological or small molecule. Before the first drug administration, mucosal colonic biopsies and a peripheral blood sample were obtained. At the end of induction, colonic biopsies and peripheral blood were sampled again. Patients starting adalimumab (n=2), infliximab (n=3), vedolizumab (n=11), ustekinumab (n=6), ozanimod (n=2) and the JAK inhibitors filgotinib (n=3) and tofacitinib (n=3) were included. Endoscopic improvement was defined as a Mayo endoscopic subscore of 0-1 at the end of induction. From the biopsies, a single-cell suspension was made. Intestinal and circulating immune cells were characterized via flow cytometry. Statistical analysis was performed using a paired t-test. Results Independent of the mechanism of action (MOA), patients responding to therapy showed a decrease of colonic granulocytes (neutrophils (p<0.0001) (Figure 1A), basophils (p<0.0001) (Figure 1B) and eosinophils (p=0.008) (Figure 1C)), active eosinophils (p=0.002) (Figure 1D)), B cells (p=0.05) (Figure 1E), regulatory T cells (p<0.0001) (Figure 1F) and T helper (Th) 2 cells (p=0.02) (Figure 1G), balanced with an increase of Th1 cells (p=0.03) (Figure 1H). In peripheral blood, eosinophils increased in patients not responding to therapy (p=0.05) (Figure 1I). Furthermore, we observed that only patients starting vedolizumab (n=11) showed a decrease in colonic eosinophils (p=0.02) (Figure 1J), active eosinophils (p=0.002) (Figure 1K), B cells (p=0.03) (Figure 1L) and T cells (p=0.004) (Figure 1M). Considering only non-vedolizumab patients (n=19), we did not observe this effect. Conclusion UC patients responding to advanced therapies showed a different intestinal immune cell distribution compared to non-responders, regardless of MOA. Vedolizumab therapy furthermore decreased several mucosal immune cell subsets that migrate to the gut through α4β7-MAdCAM-1 binding. While the effect of vedolizumab on B cells and T cells was previously described, we have now potentially identified an additional eosinophil-reducing effect in the colon.

Correlation between the Eosinophil Colonic Mucosa Density and Severity of Ulcerative Colitis

Background: The inflammatory process of ulcerative colitis (UC) involves eosinophils. Eosinophils are not only related to the severity of UC but also to clinical improvement. The role of eosinophils in colonic mucosa has not been fully understood. This study aims to determine the correlation between the density of eosinophils in the colonic mucosa and the severity of ulcerative colitis.Method: This is a prospective cross-sectional study with consecutive sampling between August 2020 and July 2021. The subjects were UC inpatients/outpatients at Dr. Sardjito Hospital who met the inclusion and exclusion criteria. The number and location of the biopsies are determined based on a colonoscopy performed by a Gastroenterology-Hepatology Consultant. An Anatomic Pathology Specialist examined the eosinophil colonic tissue. The severity of UC was classified using the Truelove Witts score. Data analysis using a computer program with a p-value 0.05 was considered statistically significant.Results: There are 3 UC severity categories according to the Truelove Witts score: 22 mild (45.8%), 9 moderate (18.8%), and 17 severe (35.4%). Seven participants (14.6%) had eosinophilia, with a median eosinophilia score of 203.33 cells/microL (0–1470 cells/microL). Five participants (10.4%) with colonic mucosal eosinophilia, with a median value of 14.13 cells/HPF (0–172 cells/HPF). The density of colonic mucosal eosinophils and the severity of UC had a moderate connection (r = 0.396; p = 0.005).Conclusion: There is a significant correlation between the density of eosinophils in the colonic mucosa and the severity of UC.

DOP09 Eosinophils exert a pro-inflammatory role in a chronic DSS colitis model without an impact on fibrosis

Abstract Background Eosinophils might play a pro-inflammatory role in inflammatory bowel disease (IBD). However, the role of eosinophils in intestinal fibrosis remains poorly understood, although a pro-fibrotic function has been hypothesized based on data outside the gastrointestinal tract. Therefore, we aimed to unravel the role of eosinophils in chronic intestinal inflammation and fibrosis and to explore eosinophil depletion as a potential therapeutic target. Methods A 3-cycles chronic dextran sodium sulphate (DSS) model was induced in 6-8-week-old C57BL/6 wild type mice. Mice received 3 DSS cycles (1.5% - 2.00% - 2.00%) in which 1 DSS cycle consisted of 1 week of DSS administration followed by 2 weeks of recovery. During the 3 cycles, and starting 3 days prior to colitis induction, anti-CCR3 antibody or isotype injections were given twice weekly to study the effect of the eosinophil depletion (total of 18 injections). The disease activity index (DAI; weight loss, stool consistency and presence of blood) was determined twice weekly. At sacrifice, colonic damage was scored macroscopically (presence of hyperaemia, adhesions and length and degree of colon affected by inflammation) and colonic single cells were isolated and fluorescently stained for flow cytometry. Eosinophils were thereby identified as CD45+ CD11b+ Siglec-F+ CD117- cells. Lastly, a histological active disease score was determined comprising of the sum of neutrophil infiltration, mononuclear cell infiltration, changes in mucosal architecture, goblet cell loss and epithelial defects (Creyns et al., 2019). Intestinal fibrosis was assessed via colon weight/length ratio, COL1A1 gene expression and collagen deposition with a Martius Scarlet Blue (MSB) staining and a colorimetric hydroxyproline assay. Results Blood and colonic eosinophil depletion via anti-CCR3 injections was confirmed via flow cytometry (figure 1). The DAI in the eosinophil depleted group was decreased compared to the isotype injected group (area under the curve 115.4 ± 29 vs 160.6 ± 28; p=0.02). A similar trend was seen in the macroscopic damage score (2.0 ± 1.3 vs 3.9 ± 2.1; p=0.08). Furthermore, a lower histological active disease score was found in the mice in which the eosinophils were depleted compared to the isotype injected mice (8.8 ± 0.8 vs 12.8 ± 1.5; p=0.002) (figure 2). Lastly, no differences in the parameters for fibrosis between the anti-CCR3 injected and isotype injected groups were observed (figure 3). Conclusion Eosinophil depletion via intraperitoneal anti-CCR3 injections resulted in partial protection from intestinal inflammation in chronic DSS, and could therefore be further explored as a potential therapeutic agent. In contrast, eosinophil depletion does not seem to have any anti-fibrotic effect

The Relationship between Eosinophil Density in the Colonic Mucosa and Eosinophil Blood Count in Children: A Cross-Sectional Study.

Eosinophils are found in the mucosa of the healthy gastrointestinal tract, but they also often accompany gastrointestinal diseases. We hypothesized that a positive correlation exists between blood eosinophil count and colonic eosinophil mucosal density in children. Electronic health records regarding 181 colonoscopies, performed with biopsy in the years 2019-2022, were screened for information on blood and colonic eosinophil count, age, sex, diagnoses, weight, height, white blood cell (WBC) count, serum C-reactive protein (CRP), and total IgE concentration. The median age (IQR) of the 107 included children (109 colonoscopies) was 12.4 years (8.1-15.5); 32 presented with blood eosinophilia (29.3%). The median eosinophil density/high-power field in the colonic mucosa was 22.5 (9-31). We found a weak correlation between colonic mucosal eosinophil density and blood eosinophil count (r = 0.295, 95% CI 0.108-0.462, p = 0.0018). This association was more pronounced in patients with elevated CRP (r = 0.529, 95% CI 0.167-0.766, p = 0.0054) and older than 12.4 years (r = 0.448, 95% CI 0.197-0.644, p = 0.00068). Peripheral blood eosinophilia might hint at increased mucosal colonic eosinophil density, especially in older children and in the presence of systemic inflammation. However, it seems unlikely that blood and colonic eosinophilia are strongly linked in younger children. Studies in adults are warranted.

Potent CCR3 Receptor Antagonist, SB328437, Suppresses Colonic Eosinophil Chemotaxis and Inflammation in the Winnie Murine Model of Spontaneous Chronic Colitis.

Eosinophils and their regulatory molecules have been associated with chronic intestinal inflammation and gastrointestinal dysfunctions; eosinophil accumulation in the gut is prominent in inflammatory bowel disease (IBD). The chemokine receptor CCR3 plays a pivotal role in local and systemic recruitment and activation of eosinophils. In this study, we targeted CCR3-ligand interactions with a potent CCR3 receptor antagonist, SB328437, to alleviate eosinophil-associated immunological responses in the Winnie model of spontaneous chronic colitis. Winnie and C57BL/6 mice were treated with SB328437 or vehicle. Clinical and histopathological parameters of chronic colitis were assessed. Flow cytometry was performed to discern changes in colonic, splenic, circulatory, and bone marrow-derived leukocytes. Changes to the serum levels of eosinophil-associated chemokines and cytokines were measured using BioPlex. Inhibition of CCR3 receptors with SB328437 attenuated disease activity and gross morphological damage to the inflamed intestines and reduced eosinophils and their regulatory molecules in the inflamed colon and circulation. SB328437 had no effect on eosinophils and their progenitor cells in the spleen and bone marrow. This study demonstrates that targeting eosinophils via the CCR3 axis has anti-inflammatory effects in the inflamed intestine, and also contributes to understanding the role of eosinophils as potential end-point targets for IBD treatment.

Prognostic Value of Colonic Tissue and Blood Eosinophils in Ulcerative Colitis.

It has been suggested that eosinophils may be a prognostic marker of disease outcome in ulcerative colitis (UC), but conflicting data exist. The objective was to investigate the extent of mucosal eosinophils and peripheral blood eosinophil count in newly diagnosed UC patients and to investigate its predictive value in short- and long-term disease outcomes. The degree of eosinophilia in baseline colonic biopsies and blood of newly diagnosed UC patients was retrospectively analyzed. It was investigated if tissue and blood eosinophilia could be a marker of a severe phenotype of UC, defined as the need for corticosteroids or immunomodulators in the first year or treatment with therapeutic monoclonal antibodies or colectomy during follow-up. Time to therapeutic monoclonal antibodies and time to colectomy were also evaluated as outcomes. There were 103 UC patients (median age 26 years) included. Median tissue peak eosinophil count (PEC) was 70.0 and median peripheral blood eosinophil count was 0.3 × 109/L at diagnosis. Tissue PEC (r = -0.161, P = .104) and blood eosinophil count (r = 0.022, P = .877) were not correlated with the severity of histologic inflammation. Logistic regression analyses did not identify PEC and blood eosinophil count as predictors of more severe disease outcomes. Tissue PEC and peripheral blood eosinophil count did not predict the time the initiation of therapeutic monoclonal antibodies or colectomy. Baseline tissue or peripheral blood eosinophils are not markers of disease activity and cannot be used as a predictor of severe disease outcomes in both adults and children with UC.

Evaluating Eosinophilic Colitis as a Unique Disease Using Colonic Molecular Profiles: A Multi-Site Study

Colonic eosinophilia, an enigmatic finding often referred to as eosinophilic colitis (EoC), is a poorly understood condition. Whether EoC is a distinct disease or a colonic manifestation of eosinophilic gastrointestinal diseases (EGIDs) or inflammatory bowel disease (IBD) is undetermined. Subjects with EoC (n= 27) and controls (normal [NL, n= 20], Crohn's disease [CD, n= 14]) were enrolled across sites associated with the Consortium of Eosinophilic Gastrointestinal Disease Researchers. EoC was diagnosed as colonic eosinophilia (ascending ≥100, descending ≥85, sigmoid ≥65 eosinophils/high-power field) with related symptoms. Colon biopsies were subjected to RNA sequencing. Associations between gene expression and histologic features were analyzed with Spearman correlation; operational pathways and cellular constituents were computationally derived. We identified 987 differentially expressed genes (EoC transcriptome) between EoC and NL (>1.5-fold change, P< .05). Colonic eosinophil count correlated with 31% of EoC transcriptome, most notably with CCL11 and CLC (r= 0.78 and 0.77, P < .0001). Among EoC and other EGIDs, there was minimal transcriptomic overlap and minimal evidence of a strong allergic type 2 immune response in EoC compared with other EGIDs. Decreased cell cycle and increased apoptosis in EoC compared with NL were identified by functional enrichment analysis and immunostaining using Ki-67 and cleaved caspase-3. Pericryptal circumferential eosinophil collars were associated with the EoC transcriptome (P < .001). EoC transcriptome-based scores were reversible with disease remission and differentiated EoC from IBD, even after controlling for colonic eosinophil levels (P < .0001). We established EoC transcriptomic profiles, identified mechanistic pathways, and integrated findings with parallel IBD and EGID data. These findings establish EoC as a distinct disease compared with other EGIDs and IBD, thereby providing a basis for improving diagnosis and treatment.

CCL11 exacerbates colitis and inflammation-associated colon tumorigenesis.

CCL11, also known as eotaxin-1, is described as an eosinophil chemoattractant, which has been implicated in allergic and Th2 inflammatory diseases. We have reported that CCL11 is significantly increased in the serum of inflammatory bowel disease (IBD) patients, colonic eosinophils are increased and correlate with tissue CCL11 levels in ulcerative colitis patients, and CCL11 is increased in dextran sulfate sodium (DSS)-induced murine colitis. Here, we show that CCL11 is involved in the pathogenesis of DSS-induced colitis and in colon tumorigenesis in the azoxymethane (AOM)-DSS model of colitis-associated carcinogenesis (CAC). Ccl11-/- mice exposed to DSS then allowed to recover had significantly less body weight loss and a decrease in histologic injury versus wild-type (WT) mice. In the AOM-DSS model, Ccl11-/- mice exhibited decreased colonic tumor number and burden, histologic injury, and colonic eosinophil infiltration versus WT mice. Ccl11 is expressed by both colonic epithelial and lamina propria immune cells. Studies in bone marrow chimera mice revealed that hematopoietic- and epithelial-cell-derived CCL11 were both important for tumorigenesis in the AOM-DSS model. These findings indicate that CCL11 is important in the regulation of colitis and associated carcinogenesis and thus anti-CCL11 antibodies may be useful for treatment and cancer chemoprevention in IBD.

Colonic mucosal eosinophilia in children without inflammatory bowel disease

Children undergoing colonoscopy and mucosal biopsies may show increased colonic mucosal eosinophils, which may or may not be associated with inflammatory bowel disease. There is not much clinical data on American children who have isolated increased colonic mucosal eosinophils. We sought to study the clinical correlates of children without inflammatory bowel disease who show increased mucosal eosinophils to understand their clinical presentation, etiological associations, and outcome. A retrospective analysis of children seen at a tertiary-level Children's hospital was performed by reviewing their medical charts and extracting pertinent data. There were 110 children in the study who had increased colonic mucosal eosinophils. Most children presented with abdominal pain, but several of them also had constipation, blood in stools, and diarrhea. Food allergies, irritable bowel syndrome, asthma, and lactase deficiency were the top four conditions present in these patients. Pathology of the colonic distribution revealed involvement of more than two colonic regions in 86% of the subjects, and only two subjects showing epithelial or crypt involvement by eosinophils. All subjects had a good outcome. Children with colonic mucosal eosinophilia (CME) who do not have an inflammatory bowel disease most frequently present with abdominal pain and primarily an increase of lamina propria eosinophils in two or more colonic regions. Based on the etiological associations we noted in the study, a work-up of children with CME may encompass detailed history for functional gastrointestinal disorders and lactose intolerance, testing for food and environmental allergies, stool examination for parasites, and peripheral blood counts. Almost all children had resolution of symptoms in the studied period suggesting that CME in children has a good clinical outcome.

Assessing Phenotypic Heterogeneity in Intestinal Tissue Eosinophils.

Eosinophils are primarily tissue-dwelling leukocytes. Utilization of flow cytometry techniques applied to digested tissues is expanding the scope of organs within which eosinophils are identified at baseline and is providing deeper insights into categorizing phenotypically and functionally distinct tissue-resident eosinophil subpopulations in health and disease. Here we describe a tissue digestion protocol and flow cytometry gating strategy for identification and isolation of tissue eosinophils from the small intestine of mice. This protocol is also amenable to the isolation and characterization of colonic eosinophils, and of intestinal eosinophils from human resected tissues.

Allerjik Proktokolit Öngörüsünde Hematolojik Parametrelerin Kullanımı

Aim: Allergic proctocolitis (AP) is a common cause of rectal bleeding in infants. There is no diagnostic tool specific to the disease. The aim of the study was to evaluate hemogram parameters as a marker of inflammation in patients with AP.Material and Methods: The files of patients who were exclusively breastfed and diagnosed as food protein induced AP were examined retrospectively. A hundred and fifty patients diagnosed with AP were included in the study. The same number of healthy babies formed the control group. Parameters in complete blood count were compared between patient and control groups. Rectosigmoidoscopic examination was performed to confirm the diagnosis in patients who could not achieve complete improvement with diet therapy, and hemogram parameters were evaluated according to eosinophilic infiltration in biopsies.Results: The mean platelet volume (MPV) values (p&amp;lt;0.001) and eosinophil percentages (p=0.001) of the AP group were higher than the control group. The mean hemoglobin values of the AP group were statistically significantly lower than the control group (p&amp;lt;0.001). No statistically significant difference was found between patient and control groups in terms of white blood cell (WBC) count, platelet count, platelet distribution width (PDW) and neutrophil/lymphocyte ratio (NLR). WBC count, platelet count, hemoglobin, MPV and C-reactive protein (CRP) values were similar between groups of patients according to the number of eosinophils in colon biopsies.Conclusion: We observed a significantly higher MPV values and eosinophil percentages in patients with AP. These parameters maybe helpful in diagnosis of AP.

The relationship between mucosal inflammatory cells, specific symptoms, and psychological functioning in youth with irritable bowel syndrome

Both mucosal inflammation and psychologic dysfunction have been implicated in irritable bowel syndrome (IBS). While some relationships between inflammation (mast cells and eosinophils) and depression have been reported in adults with IBS, relationships between inflammation and psychologic function have not been studied in children and adolescents. The aims of the current study were to: (1) assess densities of colonic mast cells, eosinophils, and TH17 cells in youth with IBS; and, (2) explore relationships between these cells and specific IBS symptoms and psychologic functioning. Utilizing previously obtained biopsies from the descending and rectosigmoid colons, densities were determined for mast cells, eosinophils, and TH17 cells, respectively, in 37 youth with IBS and 10 controls. In IBS patients, densities were assessed in relation to specific IBS symptoms and in relation to self-report anxiety and depression scores. In both the descending and rectosigmoid colons, densities of mast cells, eosinophils, and TH17 cells were higher in IBS patients as compared to controls. In IBS patients, rectosigmoid mast cell density was higher in those reporting pain relief with defecation. Also, in IBS patients, rectosigmoid eosinophilia was associated with higher anxiety scores and eosinophil density correlated with depression scores. In the descending colon, eosinophil and mast cell densities both correlated with depression scores. In conclusion, mucosal inflammation (mast cells and eosinophils) is associated with pain relief with defecation and with anxiety and depression in youth with IBS.

Prodromal Intestinal Events in Alzheimer's Disease (AD): Colonic Dysmotility and Inflammation Are Associated with Enteric AD-Related Protein Deposition.

Increasing evidence suggests that intestinal dysfunctions may represent early events in Alzheimer’s disease and contribute to brain pathology. This study examined the relationship between onset of cognitive impairment and colonic dysfunctions in a spontaneous AD model before the full development of brain pathology. SAMP8 mice underwent Morris water maze and assessment of faecal output at four, six and eight months of age. In vitro colonic motility was examined. Faecal and colonic Aβ, tau proteins, α-synuclein and IL-1β were assessed by ELISA. Colonic citrate synthase activity was assessed by spectrophotometry. Colonic NLRP3, caspase-1 and ASC expression were evaluated by Western blotting. Colonic eosinophil density and claudin-1 expression were evaluated by immunohistochemistry. The effect of Aβ on NLRP3 signalling and mitochondrial function was tested in cultured cells. Cognitive impairment and decreased faecal output occurred in SAMP8 mice from six months. When compared with SAMR1, SAMP8 animals displayed: (1) impaired in vitro colonic contractions; (2) increased enteric AD-related proteins, IL-1β, active-caspase-1 expression and eosinophil density; and (3) decreased citrate synthase activity and claudin-1 expression. In THP-1 cells, Aβ promoted IL-1β release, which was abrogated upon incubation with caspase-1 inhibitor or in ASC-/- cells. Aβ decreased mitochondrial function in THP-1 cells. In SAMP8, enteric AD-related proteins deposition, inflammation and impaired colonic excitatory neurotransmission, occurring before the full brain pathology development, could contribute to bowel dysmotility and represent prodromal events in AD.

16 CCL11 EXACERBATES COLITIS VIA MODULATION OF EPITHELIAL WOUND REPAIR

Abstract Background We have shown that CCL11 (eotaxin-1), an eosinophil chemoattractant, is significantly increased in the serum of ulcerative colitis and Crohn’s disease patients vs controls and is also increased in dextran sulfate sodium (DSS)-induced murine colitis. In response to azoxymethane (AOM)-DSS, Ccl11–/– mice have significantly decreased colonic tumor number and burden, histologic injury, and colonic eosinophil infiltration vs wild-type (WT) mice. Ccl11 is expressed by isolated colonic epithelial and lamina propria immune cells. Studies in bone marrow chimera mice revealed that both hematopoietic- and epithelial-cell derived CCL11 were important for protection in the AOM-DSS model. Our aim was to assess the role of CCL11 in an injury and recovery colitis model and in an epithelial wound restitution model. Methods C57BL/6 WT and Ccl11–/– mice were exposed to 4% DSS in the drinking water for 5 days followed by 5 days of water for an injury and recovery model. Body weights were assessed daily. Histologic injury was assessed by a validated scoring system including depth and percent involvement of inflammation and crypt damage. Colonic eosinophil and neutrophil infiltration was determined by immunohistochemistry for major basic protein (MBP) and myeloperoxidase (MPO), respectively. The number of MBP- and MPO-positive cells per high-powered field (HPF) were quantified in a blinded manner. Young Adult Mouse Colon (YAMC) epithelial cells were stained with antibodies to the CCL11 receptors CCR2, CCR3, and CCR5 for assessment by flow cytometry. YAMC cell monolayers were wounded and followed for 24 h in normal media or with the addition of 100ng/mL recombinant CCL11 (rCCL11). The wound area was measured at 0 and 24 h to determine percent restitution. RNA was isolated and assessed for Ccl11 mRNA expression. Results In the injury and recovery model, Ccl11–/– mice exhibited decreased body weight loss (p&amp;lt;0.05), histologic injury (20.6 ± 1.5 vs 12.4 ± 1.6, p&amp;lt;0.001), and fewer MBP-positive cells/HPF (23.5 ± 1.4 vs 2.4 ± 0.2, p&amp;lt;0.001) vs WT mice. While colonic MPO-positive cells were increased with DSS exposure, there was no difference in Ccl11–/– mice. Naïve/unstimulated YAMC cells expressed both CCR3 and CCR5. Wounding the YAMC monolayer alone did not lead to increased Ccl11 mRNA expression. However, in the presence of rCCL11, there was a decrease in wound restitution at 24 h (48.0% ± 1.7 vs 31.3% ± 2.1, p&amp;lt;0.001). Conclusions Loss of CCL11 leads to clinical and histologic improvement in an injury and recovery colitis model. Colonic epithelial cells express both CCR3 and CCR5, and epithelial wound restitution is decreased in the presence of rCCL11. These data suggest that CCL11 has a deleterious effect on epithelial restitution leading to an exacerbation of colitis. Therefore, treatment with anti-CCL11 antibodies may be a therapeutic strategy in IBD patients.

P159 PHENOTYPIC CHARACTERIZATION OF INFLAMMATORY BOWEL DISEASE BIOPSIES REVEAL THAT MAST CELLS ARE SIGNIFICANTLY ELEVATED AND ACTIVATED IN PATIENTS WITH ULCERATIVE COLITIS

Abstract Rationale Accumulation and activation of mast cells and eosinophils have been implicated in the pathogenesis of several chronic inflammatory gastrointestinal (GI) diseases, including eosinophilic gastrointestinal diseases (EGIDs) and inflammatory bowel disease (IBD). Despite the strong association of mast cell and eosinophil numbers and activation with the pathogenesis of IBD, no further characterization of these cells has been performed. Current treatment options for IBD include aminosalicylates, antibiotics, immunomodulators, biologic agents and small molecules. These therapies are only moderately effective. A significant proportion of patients fail to respond, do not fully respond, or lose response over time. Therefore, there is significant need for more selective and effective therapy options. Siglec-8 is an inhibitory receptor selectively expressed on human eosinophils and mast cells and represents a novel target for the treatment of IBD with the anti-Siglec-8 mAb, antolimab (AK002). We aimed to quantify and evaluate the activation state of mast cells and eosinophils in colonic tissue from IBD or non-diseased patients. In addition, we quantified the production of TNFa from human colon tissue mast cells and evaluated the inhibitory activity of antolimab (AK002) on these cells. Methods Single-cell suspensions were prepared by enzymatic digestion of fresh colonic biopsies from patients clinically diagnosed with IBD (n=29) or non-diseased control tissues (n=16). Multi-color flow cytometry was performed to identify major immune cell populations and evaluate the activation state of mast cells and eosinophils. Mast cells were FACS-sorted from human colon tissue to evaluate cytokine production and inhibitory activity of antolimab. Results The percentage of mast cells and the expression of the mast cell degranulation marker CD107a were significantly increased in ulcerative colitis (UC) patient biopsy tissue compared to Crohn’s disease (CD) and non-diseased colonic tissue (Figure 1A and B). Furthermore, FACS-sorted mast cells from human colon tissue produced significant quantities of TNFa that was reduced after ex vivo antolimab treatment. Colonic tissue eosinophils were also elevated in a subset of UC and CD patient biopsies, and all UC and CD tissue eosinophils displayed increased expression of the activation marker CD11b compared to control colonic tissue. Conclusions Mast cells and eosinophils may play a significant role in driving the pathogenesis of ulcerative colitis through the production of inflammatory mediators. The high expression of Siglec-8 and the inhibitory activity against mast cells suggests that antibodies that target this receptor, such as antolimab (AK002) represent a potential novel approach for the treatment of IBD.

16 CCL11 EXACERBATES COLITIS VIA MODULATION OF EPITHELIAL WOUND REPAIR

We have shown that CCL11 (eotaxin-1), an eosinophil chemoattractant, is significantly increased in the serum of ulcerative colitis and Crohn’s disease patients vs controls and is also increased in dextran sulfate sodium (DSS)-induced murine colitis. In response to azoxymethane (AOM)-DSS, Ccl11–/– mice have significantly decreased colonic tumor number and burden, histologic injury, and colonic eosinophil infiltration vs wild-type (WT) mice. Ccl11 is expressed by isolated colonic epithelial and lamina propria immune cells. Studies in bone marrow chimera mice revealed that both hematopoietic- and epithelial-cell derived CCL11 were important for protection in the AOM-DSS model. Our aim was to assess the role of CCL11 in an injury and recovery colitis model and in an epithelial wound restitution model.

Association Between Endoscopic and Histologic Findings in a Multicenter Retrospective Cohort of Patients with Non-esophageal Eosinophilic Gastrointestinal Disorders.

Little is known about the endoscopic and histologic findings of non-esophageal eosinophilic gastrointestinal diseases (EGID). To characterize the presenting endoscopic and histologic findings in patients with eosinophilic gastritis (EG), eosinophilic gastroenteritis (EGE), and eosinophilic colitis (EC) at diagnosis and 6months after initiating the treatment. We conducted a retrospective cohort study at 6 US centers associated with the Consortium of Eosinophilic Gastrointestinal Researchers. Data abstracted included demographics, endoscopic findings, tissue eosinophil counts, and associated histologic findings at diagnosis and, when available, after initial treatment. Of 373 subjects (317 children and 56 adults), 142 had EG, 123 EGE, and 108 EC. Normal endoscopic appearance was the most common finding across all EGIDs (62% of subjects). Baseline tissue eosinophil counts were quantified in 105 (74%) EG, 36 (29%) EGE, and 80 (74%) EC subjects. The mean peak gastric eosinophil count across all sites was 87 eos/hpf for EG and 78 eos/hpf for EGE. The mean peak colonic eosinophil count for EC subjects was 76 eos/hpf (range 10-500). Of the 29% of subjects with post-treatment follow-up, most had an improvement in clinical, endoscopic, and histologic findings regardless of treatment utilized. Reductions in tissue eosinophilia correlated with improvements in clinical symptoms as well as endoscopic and histologic findings. In this large cohort, normal appearance was the most common endoscopic finding, emphasizing the importance of biopsy, regardless of endoscopic appearance. Decreased tissue eosinophilia was associated with improvement in symptoms, endoscopic, and histologic findings, showing that disease activity is reversible.

Mucosal Eosinophilia Is an Independent Predictor of Vedolizumab Efficacy in Inflammatory Bowel Diseases.

Peripheral and mucosal eosinophilia may be associated with more aggressive disease in inflammatory bowel disease (IBD) patients. Vedolizumab blocks T lymphocytes, eosinophil adhesion, and extravasation in the gastrointestinal tract. It is not known if mucosal eosinophilia is a predictor for the therapeutic efficacy of vedolizumab. This was a retrospective cohort study of IBD patients with ileal or colonic biopsies who were off steroids before starting vedolizumab. Biopsies were rereviewed by pathologists, and mean eosinophil density was quantified. Patient characteristics and steroid-free clinical response 6 months after beginning vedolizumab were determined. Features were compared between nonresponders and responders, and multivariable logistic regression was performed to identify predictors of clinical response. Of 251 IBD patients starting vedolizumab therapy, 65 patients (48% Crohn's disease, 52% ulcerative colitis) met inclusion criteria. All IBD patients not responding to vedolizumab were more likely to have a higher baseline mean eosinophil count (340 ± 156 vs 236 ± 124; P = 0.004), be previously exposed to an anti-TNF (96% vs 56%; P = 0.001), and be male (58% vs 28%; P = 0.02). Mean eosinophil counts were significantly increased in colonic biopsies in UC nonresponders (438 ± 149 vs 299 ± 145; P = 0.01). A similar trend was seen in CD nonresponders. On multivariable analysis, colonic eosinophil density and prior anti-TNF exposure-and the combination of both-were independent predictors of response. In ulcerative colitis, colonic eosinophilia and prior anti-TNF exposure were independent predictors of 6-month clinical nonresponse to vedolizumab. Mucosal eosinophil density as a novel biomarker should be explored in larger patient cohorts.Aside from the previous anti-TNF exposure, eosinophil density in the colon of patients with UC is a negative predictor for a steroid-free long-term response to vedolizumab. The degree colonic eosinophilia may be a novel biomarker that should be further explored.

Lactase Deficiency and Colonic Mucosal Eosinophilia (P19-014-19)

ObjectivesImmunological studies in patients with lactase deficiency (LD) have suggested a role of colonic mucosal inflammatory cells in causation of some of the symptoms. We hypothesized that since eosinophils are associated with symptoms of abdominal pain and diarrhea; and patients with LD frequently manifest these symptoms, there may be an increase of eosinophils in LD. Thus, our objective was to study children with LD to assess eosinophils in their colonic mucosa. MethodsWe reviewed the pathology reports of mucosal biopsies of 86 children with LD who underwent esophagogastroduodenoscopy (EGD) and colonoscopy or only EGD. Data was abstracted from the pathology reports and analyzed. Lactase enzyme testing was performed at a reference laboratory on the mucosal biopsy specimen obtained from duodenum. The reference laboratory defined the normal range of lactase enzyme as 24.5+/− 8 micromoles per minute per gram of protein (micromoles/min), and abnormal level as <15 micromoles/min. ResultsThe subjects ranged in age from 1 to 17 years and 47 (55%) were female and all subjects had abdominal pain. The lactase enzyme levels in the study subjects ranged from 0 to 13.9. All 86 subjects underwent EGD, 6 (7%) of whom had celiac disease and 10 (12%) showed increased mucosal eosinophils in the duodenal mucosa. All subjects with celiac disease had very low (<7 micromoles/min) levels of lactase. There were 52 subjects who had colonoscopy as well, and 16 (31%) of them had increased colonic mucosal eosinophils (CME), whereas 32 (62%) showed no histopathological abnormality of colonic mucosa. ConclusionsOur study found that 31% of children with lactase deficiency manifest increased colonic mucosal eosinophils. Chemical mediators secreted by eosinophils are known to mediate abdominal pain. However, to fully understand the role of other inflammatory cells in the clinical presentation of children with LD, future studies on larger numbers of subjects that assess eosinophils and mast cells are needed. Funding SourcesIntra-departmental Funding.

Eosinophilic colitis and colonic eosinophilia.

Eosinophilic colitis is a rare condition, with a prevalence rate in the USA of 2-3/100 000 persons (0.003%), but diagnosed in 0.1% of biopsies in those colonoscoped for diarrhoea. Secondary colonic eosinophilia is more common and associated with systemic, colonic and infectious diseases. In this review, the latest advances in diagnosis, treatment and prognosis are summarized and discussed. What constitutes a 'normal' count of eosinophils is poorly documented but there are recent studies that establish normal colonic eosinophil ranges as well as distinguishing histological and clinical findings in primary eosinophilic colitis and secondary colonic eosinophilia in children and adults. Primary eosinophilic colitis is rare, relatively straightforward to diagnose, but may be difficult to treat. Colonic eosinophilia may be overt in parasite infection and connective tissue disease. More subtle, secondary colonic eosinophilia is a useful biomarker for gastrointestinal diseases, such as inflammatory bowel disease, colonic spirochaetosis and collagenous colitis, but the eosinophilia may more often be overlooked. A limited number of drugs are also known to cause left sided colonic eosinophilia such as clopidogrel, ibuprofen and oestroprogestinic agents. Advances in our understanding of primary eosinophilic colitis and secondary colonic eosinophilia is progressing and if present, colonic eosinophilia should point the clinician and pathologist to a list of differential diagnoses worth considering to direct optimal management.