Evaluation of B and T lymphocytes and plasma cells in colonic mucosa from healthy dogs and from dogs with inflammatory bowel disease

Elucidating the Role of Innate and Adaptive Immune Responses in the Pathogenesis of Canine Chronic Inflammatory Enteropathy-A Search for Potential Biomarkers

Simple Summary

Canine chronic inflammatory enteropathy (CIE) is a chronic disease affecting the small or large intestine and, in some cases, the stomach of dogs. This gastrointestinal disorder is common and is characterized by recurrent vomiting, diarrhea, and weight loss in affected dogs. The pathogenesis of IBD is not completely understood. Similar to human IBD, potential disease factors include genetics, environmental exposures, and dysregulation of the microbiota and the immune response. Some important components of the innate and adaptive immune response involved in CIE pathogenesis have been described. However, the immunopathogenesis of the disease has not been fully elucidated. In this review, we summarized the literature associated with the different cell types and molecules involved in the immunopathogenesis of CIE, with the aim of advancing the search for biomarkers with possible diagnostic, prognostic, or therapeutic utility.

Abstract

Canine chronic inflammatory enteropathy (CIE) is one of the most common chronic gastrointestinal diseases affecting dogs worldwide. Genetic and environmental factors, as well as intestinal microbiota and dysregulated host immune responses, participate in this multifactorial disease. Despite advances explaining the immunological and molecular mechanisms involved in CIE development, the exact pathogenesis is still unknown. This review compiles the latest reports and advances that describe the main molecular and cellular mechanisms of both the innate and adaptive immune responses involved in canine CIE pathogenesis. Future studies should focus research on the characterization of the immunopathogenesis of canine CIE in order to advance the establishment of biomarkers and molecular targets of diagnostic, prognostic, or therapeutic utility.

Correlating Gastrointestinal Histopathologic Changes to Clinical Disease Activity in Dogs With Idiopathic Inflammatory Bowel Disease

Prior studies have failed to detect a convincing association between histologic lesions of inflammation and clinical activity in dogs with inflammatory bowel disease (IBD). We hypothesized that use of a simplified histopathologic scoring system would improve the consistency of interpretation among pathologists when describing histologic lesions of gastrointestinal inflammation. Our aim was to evaluate the correlation of histopathologic changes to clinical activity in dogs with IBD using this new system. Forty-two dogs with IBD and 19 healthy control dogs were enrolled in this retrospective study. Endoscopic biopsies from the stomach, duodenum, ileum, and colon were independently scored by 8 pathologists. Clinical disease activity was scored using the Canine Inflammatory Bowel Disease Activity Index (CIBDAI) or the Canine Chronic Enteropathy Clinical Activity Index (CCECAI), depending on the individual study center. Summative histopathological scores and clinical activity were calculated for each tissue (stomach, duodenum, ileum, and colon) and each tissue histologic score (inflammatory/morphologic feature). The correlation between CCECAI/CIBDAI and summative histopathologic score was significant ( P < .05) for duodenum ( r = 0.42) and colon ( r = 0.33). In evaluating the relationship between histopathologic scores and clinical activity, significant ( P < .05) correlations were observed for crypt dilation ( r = 0.42), lamina propria (LP) lymphocytes ( r = 0.40), LP neutrophils ( r = 0.45), mucosal fibrosis ( r = 0.47), lacteal dilation ( r = 0.39), and villus stunting ( r = 0.43). Compared to earlier grading schemes, the simplified scoring system shows improved utility in correlating histopathologic features (both summative histology scores and select histologic scores) to IBD clinical activity.

Mucosal immunity and gut microbiota in dogs with chronic enteropathy

Chronic enteropathy (CE) in dogs is a chronic and relapsing immunopathology, of unknown etiology, that usually manifests with a plethora of clinical signs reflecting the underlying heterogeneity in its pathogenesis. Alterations of the mucosal immune responses and the gut microbiota composition are thought to play an essential role in CE. Similar to humans, it is hypothesized that the breakdown in mucosal tolerance leads to aberrant and pathological immune responses toward the gut microbiota, that in turn, may contribute to the severity of disease, at least for certain CE subsets. Therefore, in this review, we discuss some of the most relevant and recent insights microbiological and immunological aspects characterizing CE in dogs.

Genome-wide association studies of inflammatory bowel disease in German shepherd dogs

Canine Inflammatory Bowel Disease (IBD) is considered a multifactorial disease caused by complex interactions between the intestinal immune system, intestinal microbiota and environmental factors in genetically susceptible individuals. Although IBD can affect any breed, German shepherd dogs (GSD) in the UK are at increased risk of developing the disease. Based on previous evidence, the aim of the present study was to identify single nucleotide polymorphisms (SNPs), which may confer genetic susceptibility or resistance to IBD using a genome-wide association study (GWAS). Genomic DNA was extracted from EDTA blood or saliva samples of 96 cases and 98 controls. Genotyping of cases and controls was performed on the Canine Illumina HD SNP array and data generated was analyzed using PLINK. Several SNPs and regions on chromosomes 7,9,11 and 13 were detected to be associated with IBD using different SNP-by-SNP association methods and FST windows approach. Searching one Mb up-and down-stream of the most significant SNPs, as identified by single SNP analysis as well as 200Kb before and after the start and the end position of the associated regions identified by FST windows approach, we identified 63 genes. Using a combination of pathways analysis and a list of genes that have been reported to be involved in human IBD, we identified 16 candidate genes potentially associated with IBD in GSD.

Immunophenotype of Peripheral Blood Lymphocytes in Dogs with Inflammatory Bowel Disease

Background

Inflammatory bowel disease (IBD) is common in dogs. Despite the known importance of intestinal lymphocytes in its pathogenesis, little is known about the role of peripheral blood lymphocytes (PBLs) in IBD.

Objectives

The aims of this study were (1) comparison of PBLs analyzed by flow cytometry (FCM) in IBD dogs and healthy controls and (2) comparison of PBLs in IBD dogs at the time of diagnosis and in dogs in clinical remission.

Animals

Whole blood samples of 19 IBD dogs at the time of diagnosis and blood samples of 6 dogs in clinical remission were collected. Ten healthy dogs served as controls.

Methods

In this prospective observational study, PBLs were analyzed with multicolor FCM by staining with a panel of anticanine and cross‐reactive monoclonal antibodies against T‐ and B‐cell differentiation antigens, including CD45, CD3, CD4, CD8α, CD8β, TCRαβ, TCRγδ, CD79αcy, and CD21.

Results

The IBD patients’ PBLs had significantly decreased percentages of TCRγδ⁺ T lymphocytes (median: healthy dogs, 3.32; IBD dogs, 0.97; P = 0.03) and CD21⁺ B cells (median: healthy dogs, 27.61; IBD dogs, 17.26; P = 0.04). There were no significant differences in PBLs between pretreatment and follow‐up samples.

Conclusions and Clinical Importance

The differences between PBLs in healthy and IBD dogs analyzed by FCM indicate an imbalance of lymphocytes with different immunologic functions and emphasize the potential value of this technique in a larger cohort of dogs. The PBLs did not differ between IBD dogs before treatment and clinically well‐controlled dogs after treatment.

Glycol methacrylate embedding for the histochemical study of the gastrointestinal tract of dogs naturally infected with Leishmania infantum

In canine visceral leishmaniasis a diffuse chronic inflammatory exudate and an intense parasite load throughout the gastrointestinal tract has been previously reported. However, these studies did not allow a properly description of canine cellular morphology details. The aim of our study was to better characterize these cells in carrying out a qualitative and quantitative histological study in the gastrointestinal tract of dogs naturally infected with Leishmania infantum by examining gut tissues embedded in glycol methacrylate. Twelve infected adult dogs were classified in asymptomatic and symptomatic. Five uninfected dogs were used as controls. After necropsy, three samples of each gut segment, including esophagus, stomach, duodenum, jejunum, ileum, cecum, colon, and rectum were collected and fixed in Carnoy's solution for glycol methacrylate protocols. Sections were stained with hematoxylin-eosin, toluidine blue borate, and periodic acid-Schiff stain. Leishmania amastigotes were detected by immunohistochemistry employed in both glycol methacrylate and paraffin embedded tissues. The quantitative histological analysis showed higher numbers of plasma cells, lymphocytes and macrophages in lamina propria of all segments of GIT of infected dogs than controls. The parasite load was more intense and cecum and colon, independently of the clinical status of these dogs. Importantly, glycol methacrylate embedded tissue stained with toluidine blue borate clearly revealed mast cell morphology, even after mast cell degranulation. Infected dogs showed lower numbers of mast cells in all gut segments than did controls. Despite the glycol methacrylate (GMA) protocol requires more attention and care than the conventional paraffin processing, this embedding procedure proved to be especially suitable for the present histological study, where it allowed to preserve and observe cell morphology in fine detail.

Evaluation of selected cytokine gene expression in colonic mucosa from dogs with idiopathic lymphocytic-plasmacytic colitis

Lymphocytic-plasmacytic colitis (LPC) is a common form of inflammatory bowel disease (IBD) affecting the canine large intestine. Cytokines are thought to be involved in the pathogenesis of IBD. However, to date, few studies have investigated cytokine mRNA expression in dogs with LPC. In this study, we investigated mRNA transcription levels of T helper cell cytokines, such as IFN-γ, IL-4, IL-17 and IL-10 and pro-inflammatory cytokines, such as IL-1β, IL-6, TNF-α, IL-8, IL-12 and IL-23, in colonic mucosa from LPC dogs by quantitative real-time RT-PCR. No significant differences were detected in cytokine mRNA expressions between dogs with LPC and controls, except for IL-23p19. Dogs with LPC failed to express a predominant cytokine profile in inflamed colonic mucosa as opposed to human IBD.

Intestinal protease-activated receptor-2 and fecal serine protease activity are increased in canine inflammatory bowel disease and may contribute to intestinal cytokine expression

Serine proteases elicit cellular responses via protease-activated receptor-2 (PAR-2) which is known to regulate inflammation and the immune response. Although the gastrointestinal tract is exposed to large amounts of proteolytic enzymes, the role of PAR-2 in canine inflammatory bowel disease (IBD) remains unclear. The objective of this study was to investigate the effects of PAR-2 activation on inflammatory cytokine/chemokine gene expression in canine intestine and the expression of intestinal PAR-2 and fecal serine protease activity in dogs with IBD. Duodenal biopsies from healthy dogs were cultured and treated ex vivo with trypsin or PAR-2 agonist peptide, and inflammatory cytokine/chemokine gene expression in the tissues was then quantified by real-time PCR. PAR-2 mRNA and protein expression levels in the duodenal mucosa were examined by real-time PCR and immunohistochemistry, respectively. Fecal serine protease activity was determined by azocasein assay. In ex vivo-cultured duodenum, trypsin and PAR-2 agonist peptide induced significant up-regulation of mRNA expression levels of interleukin-1 β (IL-1β), IL-8, mucosae-associated epithelial chemokine (MEC) and fractalkine, and this up-regulation was inhibited by a serine protease inhibitor. Duodenal PAR-2 mRNA and protein expression levels were higher in dogs with IBD than in healthy control dogs. Fecal serine protease activity was significantly elevated in dogs with IBD, and the level of activity correlated positively with the clinical severity score. These results suggest that PAR-2 may contribute to the pathogenesis of canine IBD by inducing expression of inflammatory mediators in response to luminal serine proteases.

Immunohistochemical and morphometric analysis of intestinal full-thickness biopsy samples from cats with lymphoplasmacytic inflammatory bowel disease

The distribution and numbers of CD3(+) T lymphocytes, immunoglobulin(+) plasma cells and calprotectin (L1)(+) macrophages was analyzed in full-thickness, formalin-fixed biopsy samples from the small intestine (duodenum, jejunum and ileum) and from the colon from nine cats with clinical signs of inflammatory bowel disease (IBD). All animals had lymphoplasmacytic enteritis or lymphoplasmacytic enterocolitis. Equivalent samples from the same intestinal regions from 12 healthy pet cats served as controls. Labelled cells in the lamina propria were counted by computer-aided morphometry. The different cell types were similarly distributed in both groups, but there were differences in their numbers. There were more CD3(+) T cells in the duodenum and jejunum of cats with IBD; however, the difference was only significant for the duodenum. There were significantly more IgA(+) cells in the duodenal crypt region. There were significantly more IgG(+) cells in the lower jejunal crypt region. Plasma cells expressing IgM were decreased in cats with IBD, but the difference was not significant. L1(+) macrophages were significantly decreased in the lower crypt area of the colon in cats with IBD and there was a trend to decreased L1(+) cells in the upper crypt area of the duodenum and jejunum. Comparison of the results of this study with previous findings on endoscopically-obtained duodenal biopsy samples from cats with IBD revealed some differences. These discrepancies might relate to differences between control cat populations, types of biopsy samples, methodological factors such as different counting techniques and the activity of the disease at the time of sampling.

Biomarkers in canine inflammatory bowel disease diagnostics

Canine inflammatory bowel disease (IBD) is a heterogeneous group of chronic gastrointestinal disorders. The etiology, similar to human IBD, remains unknown. Canine IBD is diagnosed by exclusion, which is a long, time and money-consuming process due to the need of elimination of other diseases presenting with similar symptoms. Therefore, a search for a specific and sensitive marker is needed to overcome these difficulties. The article is divided into 3 sections presenting up-to-date information about laboratory markers, immunohistochemical markers and changes in the neurochemical coding of the enteric nervous system, concentrating on their usefulness and future applications. Data concerning laboratory and immunohistochemical markers is based mainly on canine IBD, while the neuroimmunohistochemistry section presents knowledge from human IBD due to the lack of such studies in veterinary medicine.

Increased expression of fractalkine and its receptor CX3CR1 in canine inflammatory bowel disease and their possible role in recruitment of intraepithelial lymphocytes

The interaction between fractalkine/CX(3)CL1 and its receptor CX(3)CR1 has been reported to play an important role in various human inflammatory diseases, including inflammatory bowel disease (IBD) mediated by lymphocyte chemoattraction. The objective of this study was to investigate the role of fractalkine and CX(3)CR1 in lymphocyte migration in canine IBD. IBD was diagnosed in 34 dogs, and 19 healthy beagles were used as normal controls. We quantified intestinal mRNA and protein expression of fractalkine and CX(3)CR1 by real-time RT-PCR and ELISA, respectively, and examined the localization of fractalkine in canine intestine by immunohistochemistry. The expression of CX(3)CR1 and surface antigens on peripheral blood mononuclear cells (PBMCs) and intraepithelial lymphocytes (IELs) was analyzed by flow cytometry. Intestinal fractalkine and CX(3)CR1 mRNA was significantly up-regulated in IBD dogs compared with the healthy control dogs. In addition, fractalkine expression on intestinal epithelial cells was significantly increased in the intestinal mucosa of IBD dogs compared with the healthy dogs. CX(3)CR1(+) PBMCs were significantly elevated in IBD dogs and positively correlated with the histopathological severity of IELs infiltration. These CX(3)CR1(+) PBMCs predominantly expressed markers for cytotoxic T cells. Almost all IELs expressed CD3, and the majority of cells expressed CD8 rather than CD4, which was analogous to the CX(3)CR1(+) PBMCs. These results suggest that the fractalkine-CX(3)CR1 interaction may contribute to the pathogenesis of canine IBD through migration of IELs.

Intestinal cytokine mRNA expression in canine inflammatory bowel disease: a meta-analysis with critical appraisal

Data implicating mucosal cytokines in the pathogenesis of canine inflammatory bowel disease (IBD) are limited. The aims of the present study were to report new findings of intestinal cytokine expression in dogs with IBD and to compare these data with previous studies through meta-analysis. Cytokine mRNA abundance in intestinal biopsies collected prospectively was evaluated by using a semiquantitative RT-PCR technique. For meta-analysis, an electronic database search revealed 3 clinical trials, all of which were nonrandomized (type III) case series. Prospective analysis showed that the intestines of healthy dogs and those with IBD express numerous cytokines and that a proinflammatory expression profile is not a feature of small or large-intestinal IBD. The meta-analysis data included 158 dogs characterized as healthy (n = 45), diarrheic nonIBD dogs (n = 6), nonresponders (n = 2), small-intestinal IBD (n = 41), colonic IBD (n = 25), and chronic enteropathy (n = 39). German shepherd dogs were overrepresented in 3 of the 4 studies. Healthy dogs showed mRNA expression for most cytokines including IL2, IL4, IL5, IL10, IL12, IFNgamma, TNFalpha, and TGFbeta. Only IL12 mRNA expression was increased consistently in small-intestinal IBD, whereas IBD colitis lacked consistent patterns of expression. In summary, dogs with IBD fail to express a predominant Th1- or Th2 cytokine bias in inflamed mucosa. Heterogeneity of results among these studies might be explained by numerous factors including the method of mRNA quantification, stage of disease, and demographic differences in study populations.

Histopathological standards for the diagnosis of gastrointestinal inflammation in endoscopic biopsy samples from the dog and cat: a report from the World Small Animal Veterinary Association Gastrointestinal Standardization Group

The characterization of inflammatory change in endoscopic biopsy samples of the gastrointestinal mucosa is an increasingly important component in the diagnosis and management of canine and feline gastrointestinal disease. Interpretation has hitherto been limited by the lack of standard criteria that define morphological and inflammatory features, and the absence of such standardization has made it difficult, if not impossible, to compare results of retrospective or prospective studies. The World Small Animal Veterinary Association (WSAVA) Gastrointestinal Standardization Group was established, in part, to develop endoscopic and microscopical standards in small animal gastroenterology. This monograph presents a standardized pictorial and textual template of the major histopathological changes that occur in inflammatory disease of the canine and feline gastric body, gastric antrum, duodenum and colon. Additionally, a series of standard histopathological reporting forms is proposed, to encourage evaluation of biopsy samples in a systematic fashion. The Standardization Group believes that the international acceptance of these standard templates will advance the study of gastrointestinal disease in individual small companion animals as well as investigations that compare populations of animals.

Characterization of mast cell numbers and subtypes in biopsies from the gastrointestinal tract of dogs with lymphocytic-plasmacytic or eosinophilic gastroenterocolitis

It has been suggested but not proven that hypersensitivity type I reactions are involved in the pathogenesis of canine inflammatory bowel disease (IBD). The main effector cells in type I hypersensitivity reactions are mast cells (MCs). Canine MCs, as human MCs, can be subdivided into three subtypes according to their content of mast cell-specific proteases: tryptase (MCT), chymase (MCC), or tryptase and chymase bearing MCs (MCTC). In this study, numbers and subsets of mast cells were investigated in biopsies from the gastrointestinal tract of dogs with histopathologically confirmed lymphocytic-plasmacytic enteritis (LPE) (n=4), lymphocytic-plasmacytic colitis (LPC) (n=1) and eosinophilic gastroenterocolitis (EGE) (n=11). Paraffin sections of formalin-fixed samples from the stomach, small intestine (duodenum, jejunum, ileum) and colon were stained by using a metachromatic staining method (kresylecht-violet; KEV) and a combined enzyme histochemical and immunohistochemical technique for chymase and tryptase. Additionally, immunohistochemistry with antibodies against T cells (CD3), macrophages (myeloid/histiocyte antigen) and IgA, IgG and IgM bearing cells was conducted. Quantitative evaluation of mast cells and semiquantitative scoring of immunohistochemically stained cells were performed. Between the two histopathologically defined groups clear differences concerning mast cell numbers were detected. In most affected intestinal tissue locations of dogs with LPE/LPC a decrease in metachromatically (kresylecht-violet) stained granule-containing MCs and immunohistochemically stained MCT,C,TC was found. This reduction could be due to mast cell degranulation, a T helper cell 1 dominated reaction pattern or a "thinning out" due to increasing T cells, IgA and IgG bearing cells. Dogs with EGE displayed higher variability in mast cell numbers but most of the affected large and small intestinal locations had increased numbers of MCs. In these cases, T cells, IgA bearing cells and macrophages also increased. Increased numbers of MCs and eosinophils seen in the intestinal mucosa of dogs with EGE could indicate the presence of a type I hypersensitivity reaction (T helper cell 2 pattern) in response to dietary antigens. Changes in cell numbers occurred also in unaffected locations of dogs with LPE/LPC and EGE which showed reduced MCT,C,TC, increased KEV positive cells and partially increased leucocytes and macrophages.

Evaluation of disease activity markers in dogs with idiopathic inflammatory bowel disease

OBJECTIVES

To evaluate the clinical utility of serum tumour necrosis factor-alpha, C-reactive protein and microalbuminuria as disease activity markers in canine idiopathic inflammatory bowel disease.

METHODS

Dogs with chronic gastrointestinal disease for which no underlying cause could be identified were considered to have idiopathic inflammatory bowel disease and were included in the study. Serum tumour necrosis factor-alpha was assessed using a canine-specific ELISA, C-reactive protein by immunoturbidometric assay and quantitative microalbuminuria was analysed using a monoclonal antibody directed against canine albumin. The canine inflammatory bowel disease activity index and histopathologic grade were used to assess disease severity; biologic markers were then compared with the canine inflammatory bowel disease activity index and histopathologic grade.

RESULTS

Sixteen dogs were included in the study. C-reactive protein level was mildly elevated in 15 dogs. Microalbuminuria was elevated in two of 15 dogs, and tumour necrosis factor-alpha was not detected in any dog tested. No correlation was found between the canine inflammatory bowel disease activity index and C-reactive protein or microalbuminuria or between histopathologic grade and C-reactive protein or microalbuminuria. There was no correlation between histopathologic grade and the canine inflammatory bowel disease activity index.

CLINICAL SIGNIFICANCE

Although only a small number of dogs were evaluated, this study does not support the use of serum tumour necrosis factor-alpha measured by canine-specific ELISA or microalbuminuria in the evaluation of disease activity in dogs with idiopathic inflammatory bowel disease. Although mildly elevated in most dogs, C-reactive protein did not reflect disease severity as assessed by the canine inflammatory bowel disease activity index or histopathologic grade.

Apical junction complex protein expression in the canine colon: differential expression of claudin-2 in the colonic mucosa in dogs with idiopathic colitis

Canine idiopathic lymphocytic-plasmacytic colitis (LPC) is a well-recognized clinical and pathological entity in the dog, associated with altered immune cell populations and cytokine expression profiles. Clinical and experimental data indicate that alterations in the permeability of the intestinal epithelium contribute to the pathogenesis of a range of related conditions. The apical junction complex plays a significant role in regulating epithelial paracellular permeability, and we have characterized the distribution of a number of its component tight junction (ZO-1, occludin, claudin-2) and adherens junction (E-cadherin and beta-catenin) proteins in normal colon and colon from dogs with idiopathic LPC. ZO-1, occludin, E-cadherin, and beta-catenin exhibited a distribution in normal canine colon similar to that described previously in humans and rodents. In contrast to the situation in humans, claudin-2-specific labeling was observed in the normal canine colonic crypt epithelium, decreasing in intensity from the distal to the proximal crypt and becoming barely detectable at the luminal surface of the colon. There was little evidence for significant changes in ZO-1, occludin, E-cadherin, or beta-catenin expression in dogs affected by idiopathic LPC. However, claudin-2 expression markedly increased in the proximal crypt and luminal colonic epithelium in affected dogs, suggesting a role in the pathogenesis of canine LPC.

Clinical Assessment of Disease Activity for Canine Inflammatory Bowel Disease

Clinical indices, consisting of gastrointestinal signs and laboratory parameters, are widely used for assessing disease activity in human inflammatory bowel disease (IBD). The development of a standardized scoring index for use in dogs with IBD would be useful in the management of clinical cases, both at diagnosis and in response to medical therapy. This review provides a synopsis of current strategies used to assess IBD activity in humans and companion animals. The clinical application of a simple scoring index (e.g., canine IBD activity index [CIBDAI]) for measurement of canine IBD activity is also reviewed.

A scoring index for disease activity in canine inflammatory bowel disease

The clinical course of inflammatory bowel disease (IBD) in dogs is characterized by spontaneous exacerbations and remissions, which makes assessment of disease burden difficult. The objectives of this study were to develop a scoring system for evaluation of canine IBD activity and to validate this scoring method by correlating it to objective laboratory and histologic indices of intestinal inflammation. Fifty-eight dogs with IBD were evaluated prospectively and compared to 9 disease-free control dogs. Clinical disease activity was quantified by a simple scoring system, the canine IBD activity index (CIBDAI), and compared to serum concentrations of C-reactive protein (CRP), haptoglobin (HAP), alpha-acid glycoprotein (AGP), and serum amyloid A (SAA), as well as histology scores derived from endoscopic biopsy specimens. Forty-six dogs were available for a reevaluation of the CIBDAI, CRP HAP, and AGP, and 34 dogs had repeat analysis of SAA performed after medical therapy. Serum concentrations of CRP were significantly (P < .02) increased in dogs with CIBDAI scores > or = 5 (mild disease activity or greater) compared to controls. Among IBD dogs, the CIBDAI showed good correlation (r = 0.82, P < .0001) to both histology and HAP scores, but CRP also was a strong co-correlate of disease activity. The IBD dogs showed significantly (P < .0001) decreased CIBDAI and CRP values but significantly (P < .0001) increased HAP concentrations after medical therapy compared to pretreatment values. We conclude that the CIBDAI is a reliable measure of inflammatory activity in canine IBD and that CRP is suitable for laboratory evaluation of the effect of therapy in these patients.

Eosinophilic diseases in two Cavalier King Charles spaniels

This report describes the clinical presentation of two Cavalier King Charles spaniels with different eosinophilic diseases. The first case presented with dyspnoea and a non-productive cough, and investigations demonstrated eosinophilic bronchopneumonopathy. The second dog was referred for the investigation of haemorrhagic vomiting and diarrhoea and was eventually diagnosed with eosinophilic enteritis. Both dogs had concurrent eosinophilic stomatitis, and both responded completely to immunosuppressive glucocorticoid therapy. This report is the first to describe the concurrence of eosinophilic stomatitis and systemic eosinophilic disease in Cavalier King Charles spaniels, and suggest that this breed may be predisposed to eosinophilic syndromes.

Interobserver variation among histopathologic evaluations of intestinal tissues from dogs and cats

OBJECTIVE

To determine whether substantial interobserver variation exists among diagnostic pathologists for descriptions of intestinal mucosal cell populations and whether histopathologic descriptions accurately predict when a patient does not have clinically evident intestinal disease.

DESIGN

Comparative survey. Sample Population-14 histologic slides of duodenal, ileal, or colonic tissue from 10 dogs and 3 cats.

PROCEDURE

Each histologic slide was evaluated independently by 5 pathologists at 4 institutions. Pathologists, who had no knowledge of the tissues' origin, indicated whether slides were adequate for histologic evaluation and whether the tissue was normal or abnormal. They also identified the main infiltrating cell type in specimens that were considered abnormal, and whether infiltrates were mild, moderate, severe, or neoplastic.

RESULTS

Quality of all slides was considered adequate or superior by at least 4 of the 5 pathologists. For intensity of mucosal cellular infiltrates, there was uniformity of opinion for 1 slide, near-uniformity for 6 slides, and nonuniformity for 7 slides. Five dogs did not have clinical evidence of intestinal disease, yet the pathologists' descriptions indicated that their intestinal tissue specimens were abnormal.

CONCLUSIONS AND CLINICAL RELEVANCE

Substantial interobserver variation was detected. Standardization of pathologic descriptions of intestinal tissue is necessary for meaningful comparisons with published articles. Clinicians must be cautious about correlating clinical signs and histopathologic descriptions of intestinal biopsy specimens.

Relationships between fecal consistency and colonic microstructure and absorptive function in dogs with and without nonspecific dietary sensitivity

OBJECTIVE

To determine relationships between fecal consistency and colonic microstructure and absorptive function in dogs with and without nonspecific dietary sensitivity.

ANIMALS

12 dogs with nonspecific dietary sensitivity (affected) and 9 healthy dogs (controls).

PROCEDURE

Affected dogs were fed 4 test diets and control dogs, 3 diets for 4 weeks each in a crossover design. Fecal consistency was assessed daily. At the end of each feeding period, electrolyte and water transport were assessed, and colonic biopsy specimens were obtained for histologic examination and measurement of crypt water uptake by use of confocal microscopy.

RESULTS

Feces were consistently looser in affected dogs. In control dogs, we detected net colonic absorption of sodium and chloride and secretion of potassium and bicarbonate. Absorption of sodium and chloride was less in affected dogs, compared with controls, indicating that electrolyte transport was disrupted in affected dogs. This disruption was accentuated during feeding of diets associated with significantly poorer fecal consistency (ie, loose feces). Fecal consistency was inversely correlated with crypt water absorption, which was reduced in affected dogs. Colonic crypts were shorter and less dense in affected dogs fed diets associated with poor fecal consistency, compared with affected dogs fed other diets or with control dogs.

CONCLUSIONS AND CLINICAL RELEVANCE

Colonic transport function is a major determinant of fecal consistency in dogs. Dogs with nonspecific dietary sensitivity are particularly susceptible to diet-induced changes in absorptive function. Such changes are associated with damage to colonic microstructure, disrupted electrolyte transport, and failure to dehydrate luminal contents.

Quantitative assessment of mast cells and expression of IgE protein and mRNA for IgE and interleukin 4 in the gastrointestinal tract of healthy dogs and dogs with inflammatory bowel disease

OBJECTIVE

To characterize the mucosal IgE network in dogs affected with inflammatory bowel disease (IBD) and compare it with that for healthy dogs.

ANIMALS

9 healthy dogs and 20 dogs with IBD.

PROCEDURE

In situ hybridization of mRNA specific for IgE and interleukin 4 (IL-4) and immunohistochemical analysis for IgE protein and 2 markers of mast cells (ie, tryptase and chymase) were performed on tissue sections obtained from the gastrointestinal (GI) tract and lymph nodes of dogs.

RESULTS

Dogs with IBD had significantly more cells positive for IgE protein and more mast cells in the GI mucosa than healthy dogs. Despite this significant increase in number of cells positive for IgE, cells positive for IgE mRNA were rarely detected in the GI mucosa; most cells positive for IgE mRNA were found in mesenteric lymph nodes. Signal pattern of IL-4 mRNA was similar to that of IgE mRNA.

CONCLUSIONS AND CLINICAL RELEVANCE

The increased numbers of cells positive for IgE and mast cells in dogs with IBD suggest hypersensitivity such as hypersensitivity to bacterial or dietary-derived antigens in the intestinal lumen. Future studies need to elucidate whether this represents a cause of inflammation or is a result of the inflammatory process of IBD.

An immunohistochemical study of histiocytic ulcerative colitis in boxer dogs

Histiocytic ulcerative colitis (HUC) is an inflammatory bowel disease (IBD) that occurs predominantly in dogs of the boxer breed. The lesions are characterized by mucosal ulceration and mixed inflammatory cell infiltrate that includes the presence of periodic acid-Schiff (PAS)-positive macrophages. However, the phenotype of the inflammatory cells has not been characterized further. In the present study, immunohistochemistry and computer-aided morphometric analysis were used to define populations of leucocyte subsets in the colon of 14 boxer dogs with HUC. Biopsies from six of these dogs included both lesional and non-lesional regions. Colonic tissue from 11 dogs of various breeds without evidence of gastrointestinal disease served as controls. In HUC lesions there were significantly more IgG(+), IgG3(+), IgG4(+)plasma cells, CD3(+)T cells, MHC class II(+)cells, L1(+)cells and PAS(+)cells in the lamina propria than in both control colon and non-lesional colonic regions of affected dogs. In the epithelial compartment, goblet cells were significantly decreased in HUC lesions compared to both control and non-lesional HUC colon, and intensity of enterocyte MHC class II expression was significantly increased. These observations are similar to those documented in human IBD, especially ulcerative colitis, and suggest an important role for the mucosal immune system in the pathogenesis of canine HUC.