Immune Cell Populations in the Duodenal Mucosa of Cats with Inflammatory Bowel Disease

ACVIM consensus statement guidelines on diagnosing and distinguishing low-grade neoplastic from inflammatory lymphocytic chronic enteropathies in cats

BACKGROUND

Lymphoplasmacytic enteritis (LPE) and low-grade intestinal T cell lymphoma (LGITL) are common diseases in older cats, but their diagnosis and differentiation remain challenging.

OBJECTIVES

To summarize the current literature on etiopathogenesis and diagnosis of LPE and LGITL in cats and provide guidance on the differentiation between LPE and LGITL in cats. To provide statements established using evidence-based approaches or where such evidence is lacking, statements based on consensus of experts in the field.

ANIMALS

None.

METHODS

A panel of 6 experts in the field (2 internists, 1 radiologist, 1 anatomic pathologist, 1 clonality expert, 1 oncologist) with the support of a human medical immunologist, was formed to assess and summarize evidence in the peer-reviewed literature and complement it with consensus recommendations.

RESULTS

Despite increasing interest on the topic for clinicians and pathologists, few prospective studies were available, and interpretation of the pertinent literature often was challenging because of the heterogeneity of the cases. Most recommendations by the panel were supported by a moderate or low level of evidence. Several understudied areas were identified, including cellular markers using immunohistochemistry, genomics, and transcriptomic studies.

CONCLUSIONS AND CLINICAL IMPORTANCE

To date, no single diagnostic criterion or known biomarker reliably differentiates inflammatory lesions from neoplastic lymphoproliferations in the intestinal tract of cats and a diagnosis currently is established by integrating all available clinical and diagnostic data. Histopathology remains the mainstay to better differentiate LPE from LGITL in cats with chronic enteropathy.

Fecal S100A12 concentrations in cats with chronic enteropathies

OBJECTIVES

The aim of this study was to compare fecal S100A12 concentrations in cats diagnosed with chronic enteropathy (CE) with healthy control cats.

METHODS

This was a prospective, cross-sectional study. Forty-nine cats that had gastrointestinal signs for >3 weeks and a complete diagnostic work-up, including bloodwork, abdominal ultrasound and upper and/or lower gastrointestinal endoscopic biopsies, were enrolled into the CE group. Nineteen cats from the CE group were diagnosed with inflammatory bowel disease (IBD) or chronic inflammatory enteropathy (CIE) and 30 with alimentary lymphoma (LSA), based on histopathology results and additional testing with immunohistochemistry or molecular clonality testing with PCR if indicated. Nineteen apparently healthy control cats were included in the study. One fecal sample was collected from each cat and S100A12 concentrations were quantified by an analytically validated in-house ELISA.

RESULTS

Fecal S100A12 concentrations differed between cats with LSA (median 110 ng/g; interquartile range [IQR] 18-548) and control cats (median 4 ng/g; IQR 2-25 [P <0.001]) and between cats with IBD (median 34 ng/g; IQR 15-973) and control cats (P <0.003). S100A12 concentrations in CE cats (median 94 ng/g; IQR 16-548) were statistically significantly higher compared with control cats (P <0.001). The area under the receiver operating characteristic curve (AUROC) to separate healthy cats from CE cats was 0.81 (95% confidence interval [CI] 0.70-0.92) and was statistically significant (P <0.001). The AUROC to separate cats with IBD from cats with LSA was 0.51 (95% CI 0.34-0.68) and was not statistically significant (P = 0.9).

CONCLUSIONS AND RELEVANCE

Fecal S100A12 concentrations at the time of diagnostic investigation were higher in cats with CIE and LSA than in healthy controls but did not differ between cats with LSA and those with CIE/IBD. This study is an initial step toward evaluating a novel non-invasive marker of feline CIE. Further studies are needed to determine the diagnostic utility of fecal S100A12 concentrations in cats with CE, including comparing cats with IBD/CIE and LSA, and to compare them with cats with extra-gastrointestinal disease.

[Chronic enteropathies in cats - diagnostic and therapeutic approach]

Chronic enteropathies are characterized by persistent or recurrent gastrointestinal signs including vomiting, diarrhoea, weight loss, anorexia and lethargy for a minimum duration of 3 weeks. Diagnosis is by excluding other disease processes and includes faecal examinations, blood screenings (e. g., thyroidal, pancreatic, liver dysfunctions, investigation for infectious diseases, vitamin B₁₂ status), diagnostic imaging, histopathological evaluation using biopsies from several different gastrointestinal segments and the response to therapeutic trials. Chronic inflammatory enteropathies are classified as food-responsive enteropathy (FRE), antibiotic-responsive enteropathy (ARE), immunosuppressant-responsive or, similarly -refractory enteropathy (IRE). Small-cell (low-grade) alimentary lymphoma (LGAL), a crucial differential diagnosis, is predominantly seen in older cats. The feline chronic enteropathy activity index (FCEAI), a clinical scoring system, was established to objectively assess the severity of clinical illness and to evaluate the response to treatment. In general, the prognosis depends on the underlying aetiology. Cats diagnosed with FRE typically have a good long-term prognosis with adequate dietary management. The response to treatment varies in cats with IRE, with same cats experiencing frequent relapses of clinical signs and still others being non-responsive to treatment. Prognosis for LGAL, with adequate treatment, is usually fair to good (median survival time 510-704 days).

Differentiating Inflammatory Bowel Disease from Alimentary Lymphoma in Cats: Does It Matter?

Differentiation of feline inflammatory bowel disease and intestinal small cell lymphoma can be challenging, and some clinicians argue that it is unnecessary because prognosis and treatment are similar. Differentiation of feline inflammatory bowel disease and intestinal small cell lymphoma can be challenging and some clinicians argue that it is unnecessary since prognosis and treatment are similar. Altough the body of research on this topic has increased over time, we still know little about etiopathogenesis, progression, alternative treatment modalities and prognosis of the different forms of FCE. While differentiating IBD from SCL might not alter a single patients' disease course, further research efforts are required to alter the disease course for our feline patient population as a whole.

Feline chronic enteropathy

Feline chronic enteropathy is a common disorder, especially in the senior cat population, with rising incidence over the past decade. Feline chronic enteropathy is considered an umbrella term comprising different diseases including food-responsive enteropathy, idiopathic inflammatory bowel disease and alimentary small cell lymphoma. However, differentiation between those diseases is often difficult in practice. This review will discuss the clinical approach to cats with chronic enteropathy, state-of-the-art diagnostic tests and pitfalls thereof as well as current therapeutic approaches. Although, much of the etiopathogenesis is still unknown, increased research efforts in this field have brought new insights into diagnostic and therapeutic options for these cats.

Feline comorbidities: What do we really know about feline triaditis?

PRACTICAL RELEVANCE

Feline triaditis describes concurrent pancreatitis, cholangitis and inflammatory bowel disease (IBD). The reported prevalence is 17-39% in ill referral patients. While the aetiology is poorly understood, it is known to include infectious, autoimmune and physical components. What is not known is whether different organs are affected by different diseases, or the same process; indeed, triaditis may be part of a multiorgan inflammatory disease. Feline gastrointestinal tract anatomy plays its role too. Specifically, the short small intestine, high bacterial load and anatomic feature whereby the pancreatic duct joins the common bile duct before entering the duodenal papilla all increase the risk of bacterial reflux and parenchymal inflammation. Inflammation may also be a sequela of bowel bacterial translocation and systemic bacteraemia.

DIAGNOSTIC CHALLENGES

Cholangitis, pancreatitis and IBD manifest with overlapping, vague and non-specific clinical signs. Cholangitis may be accompanied by increased serum liver enzymes, total bilirubin and bile acid concentrations, and variable ultrasonographic changes. A presumptive diagnosis of pancreatitis is based on increased serum pancreatic lipase immunoreactivity or feline pancreas-specific lipase, and/or abnormal pancreatic changes on ultrasonography, though these tests have low sensitivity. Diagnosis of IBD is challenging without histopathology; ultrasound findings vary from normal to mucosal thickening or loss of layering. Triaditis may cause decreased serum folate or cobalamin (B12) concentrations due to intestinal disease and/or pancreatitis. Triaditis can only be confirmed with histopathology; hence, it remains a presumptive diagnosis in most cases.

EVIDENCE BASE

The literature on feline triaditis, pancreatitis, cholangitis and IBD is reviewed, focusing on histopathology, clinical significance and diagnostic challenges. Current management recommendations are provided. Further studies are needed to understand the complex pathophysiology, and in turn improve diagnosis and treatment.

Triaditis: Truth and Consequences

Clinical findings with triaditis and individual disease components overlap and may include hyporexia, weight loss, lethargy, vomiting, diarrhea, dehydration, icterus, abdominal pain, thickened bowel loops, pyrexia, dyspnea, and shock. A definitive diagnosis of triaditis requires histologic confirmation of inflammation in each organ, but this may not be possible because of financial or patient-related constraints. Evidence-based data indicate that histologic lesions of triaditis are present in 30% to 50% of cats diagnosed with pancreatitis and cholangitis/inflammatory liver disease. Treatment of triaditis is based on the overall health status of the patient and the type and severity of disease in component organs.

Results of histopathology, immunohistochemistry, and molecular clonality testing of small intestinal biopsy specimens from clinically healthy client-owned cats

Background

Histopathology, immunohistochemistry, and molecular clonality testing are metrics frequently used to diagnose chronic enteropathy (CE) in cats. However, normal values for these metrics have been based mainly on samples from cats that were relatively young, specific pathogen‐free, or both.

Objectives

To describe results of histopathology, immunohistochemistry, and clonality testing of endoscopically‐derived biopsy specimens of the upper small intestinal tract from a cohort of clinically healthy client‐owned cats.

Animals

Twenty clinically healthy client‐owned cats ≥3 years of age.

Methods

Tissue specimens were collected from the stomach and duodenum and evaluated single blinded by a board‐certified pathologist. In addition, samples were evaluated by routine immunohistochemistry and clonality testing. Cats were followed after the procedure for signs of CE.

Results

Integrated results from histopathology, immunohistochemistry, and clonality testing were interpreted as consistent with small cell lymphoma (SCL; n = 12), emerging SCL (n = 1), lymphocytic enteritis (n = 6), and pseudoclonality (n = 1). On follow‐up, 3 cats eventually developed clinical signs of CE, of which 2 were euthanized 295 and 654 days post‐endoscopy. The remaining 17 cats did not show clinical signs of CE after a median of 709 days (range, 219‐869 days).

Conclusions and Clinical Importance

Intestinal biopsy specimens from clinically healthy client‐owned cats commonly had abnormal findings on histopathology, immunohistochemistry, clonality testing, or some combination of these without apparent clinical relevance. Current diagnostic metrics for diagnosing CE in cats may need modification to be applicable to the general population of cats.

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.

Prostaglandin E2 secreted from feline adipose tissue-derived mesenchymal stem cells alleviate DSS-induced colitis by increasing regulatory T cells in mice

BACKGROUND

Inflammatory bowel disease (IBD) is an intractable autoimmune disease, relatively common in cats, with chronic vomiting and diarrhea. Previous studies have reported that mesenchymal stem cells (MSCs) alleviate inflammation by modulating immune cells. However, there is a lack of research on cross-talk mechanism between feline adipose tissue-derived mesenchymal stem cells (fAT-MSCs) and immune cells in IBD model. Hence, this study aimed to evaluate the therapeutic effects of fAT-MSC on mice model of colitis and to clarify the therapeutic mechanism of fAT-MSCs.

RESULTS

Intraperitoneal infusion of fAT-MSC ameliorated the clinical and histopathologic severity of colitis, including body weight loss, diarrhea, and inflammation in the colon of Dextran sulfate sodium (DSS)-treated mice (C57BL/6). Since regulatory T cells (Tregs) are pivotal in modulating immune responses and maintaining tolerance in colitis, the relation of Tregs with fAT-MSC-secreted factor was investigated in vitro. PGE₂ secreted from fAT-MSC was demonstrated to induce elevation of FOXP3 mRNA expression and adjust inflammatory cytokines in Con A-induced feline peripheral blood mononuclear cells (PBMCs). Furthermore, in vivo, FOXP3+ cells of the fAT-MSC group were significantly increased in the inflamed colon, relative to that in the PBS group.

CONCLUSION

Our results suggest that PGE₂ secreted from fAT-MSC can reduce inflammation by increasing FOXP3+ Tregs in mice model of colitis. Consequently, these results propose the possibility of administration of fAT-MSC to cats with not only IBD but also other immune-mediated inflammatory diseases.

Feline low-grade alimentary lymphoma: an emerging entity and a potential animal model for human disease

BACKGROUND

Low-grade alimentary lymphoma (LGAL) is characterised by the infiltration of neoplastic T-lymphocytes, typically in the small intestine. The incidence of LGAL has increased over the last ten years and it is now the most frequent digestive neoplasia in cats and comprises 60 to 75% of gastrointestinal lymphoma cases. Given that LGAL shares common clinical, paraclinical and ultrasonographic features with inflammatory bowel diseases, establishing a diagnosis is challenging. A review was designed to summarise current knowledge of the pathogenesis, diagnosis, prognosis and treatment of feline LGAL. Electronic searches of PubMed and Science Direct were carried out without date or language restrictions.

RESULTS

A total of 176 peer-reviewed documents were identified and most of which were published in the last twenty years. 130 studies were found from the veterinary literature and 46 from the human medicine literature. Heterogeneity of study designs and outcome measures made meta-analysis inappropriate. The pathophysiology of feline LGAL still needs to be elucidated, not least the putative roles of infectious agents, environmental factors as well as genetic events. The most common therapeutic strategy is combination treatment with prednisolone and chlorambucil, and prolonged remission can often be achieved. Developments in immunohistochemical analysis and clonality testing have improved the confidence of clinicians in obtaining a correct diagnosis between LGAL and IBD. The condition shares similarities with some diseases in humans, especially human indolent T-cell lymphoproliferative disorder of the gastrointestinal tract.

CONCLUSIONS

The pathophysiology of feline LGAL still needs to be elucidated and prospective studies as well as standardisation of therapeutic strategies are needed. A combination of conventional histopathology and immunohistochemistry remains the current gold-standard test, but clinicians should be cautious about reclassifying cats previously diagnosed with IBD to lymphoma on the basis of clonality testing. Importantly, feline LGAL could be considered to be a potential animal model for indolent digestive T-cell lymphoproliferative disorder, a rare condition in human medicine.

Correlation between the FCEAI and diagnostic parameters in chronic enteropathies in 147 cats (2006-2012)

OBJECTIVE

The Feline Chronic Enteropathy Activity Index (FCEAI) has been established as a quantitative index for disease activity in chronic enteropathies in cats. A definite diagnosis is aimed at histology with initial exclusion of extraintestinal causes by laboratory examinations, diagnostic imaging and endoscopy. The study aimed to examine diagnostic parameters and FCEAI in chronic gastroenteropathies.

MATERIALS AND METHODS

A retrospective case review of 147 cats with chronic enteropathies was performed. In all patients, the FCEAI was established and endoscopy performed including biopsies and duodenal cytology. Histopathologic reports were reviewed for the diagnosis of lymphoma and architectural changes (epithelial integrity, villi/gland atrophy, intestinal crypt atrophy, lymphangiectasia, epitheliotropism/infiltration of intraepithelial lymphocytes). A cytopathologic score (CS) and histopathologic score (HS) regarding lymphocytic intestinal infiltration were assigned. Statistical dependency analysis was used to determine correlations between the FCEAI, lymphoma, architectural changes, CS, HS, serum concentrations of cobalamin, folate and albumin.

RESULTS

The 147 cats consisted of predominately European Shorthair cats (n = 126), were mostly castrated (n = 127) and had a mean age of 9.8 (1-17) years. For the proven lymphoma group (12.2%; n = 18) and the non-lymphoma group a mean FCEAI of 7.3 (4-17) and 6.6 (2-13), respectively, was established. The FCEAI showed a low correlation with the CS (p = 0.010; R = 0.22) and intestinal villous atrophy (n = 121; p = 0.035; R = 0.19). Cats with a CS of 0 had a significant lower FCEAI score (p = 0.015) than cats with all other CSs. The histo- and cytopathologic scores were highly related (p < 0.001; R = 0.43). The gastric intraepithelial lymphocytic infiltration (n = 131) was significantly correlated to serum folate (p = 0.014; R = -0.56) and albumin (p = 0,048; R = -0.20).

CONCLUSION

The FCEAI showed only a few correlations. Not only the grade of inflammation, but also the histologic architectural changes are of importance.

Cats are not small dogs: is there an immunological explanation for why cats are less affected by arthropod-borne disease than dogs?

It is widely recognized that cats appear to be less frequently affected by arthropod-borne infectious diseases than dogs and share fewer zoonotic pathogens with man. This impression is supported by the relative lack of scientific publications related to feline vector-borne infections. This review explores the possible reasons for the difference between the two most common small companion animal species, including the hypothesis that cats might have a genetically-determined immunological resistance to arthropod vectors or the microparasites they transmit. A number of simple possibilities might account for the lower prevalence of these diseases in cats, including factors related to the lifestyle and behaviour of the cat, lesser spend on preventative healthcare for cats and reduced opportunities for research funding for these animals. The dog and cat have substantially similar immune system components, but differences in immune function might in part account for the markedly distinct prevalence and clinicopathological appearance of autoimmune, allergic, idiopathic inflammatory, immunodeficiency, neoplastic and infectious diseases in the two species. Cats have greater genetic diversity than dogs with much lower linkage disequilibrium in feline compared with canine breed groups. Immune function is intrinsically related to the nature of the intestinal microbiome and subtle differences between the canine and feline microbial populations might also impact on immune function and disease resistance. The reasons for the apparent lesser susceptibility of cats to arthropod-borne infectious diseases are likely to be complex, but warrant further investigation.

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.

Design of a simplified histopathologic model for gastrointestinal inflammation in dogs

Significant interobserver variability in the diagnostic interpretation of endoscopic gastrointestinal (GI) specimens exists even with the use of World Small Animal Veterinary Association (WSAVA) standardization criteria. Chi-square analyses compared the extent of pathologists' agreement for microarchitectural features of inflammation in endoscopic specimens obtained from 253 animals of the original WSAVA study. Patterns of agreement between pathologists were classified as broad (3/4 pathologists agreed), dichotomous (2/4 pathologists agreed), or divergent (no agreement between pathologists). The simplified model for GI inflammation was based on those parameters for which the pathologists had either broad or minimally divergent opinions of histopathologic significance. In this model, the parameters chosen were as follows: gastric parameters (intraepithelial lymphocytes [IELs], lamina propria [LP] infiltrates, and mucosal fibrosis), duodenal parameters (villus atrophy, epithelial injury, IELs, crypt changes, and LP infiltrates), and colonic parameters (epithelial injury, crypt dilation, fibrosis, LP infiltrates, and goblet cell depletion). Preliminary data using this simplified model showed excellent correlation between pathologists in defining the presence and extent of GI inflammation in dogs.

Measurement of IL-12 (p40, p35), IL-23p19, and IFN-γ mRNA in duodenal biopsies of cats with inflammatory enteropathy

Background

Dietary hypersensitivity and inflammatory bowel disease (IBD) are important causes of chronic vomiting and diarrhea in cats. IL‐23 has been recently found to be a key factor in the immunopathogenesis of IBD in humans but the involvement in IBD has not been investigated in cats.

Hypothesis/Objectives

Expression of genes encoding Il‐12p35 and p40, IL‐23p19, and IFN‐γ may be up‐regulated in duodenal biopsy specimens taken from cats with histologic evidence of inflammation.

Animals and Methods

Duodenal biopsy specimens were collected from control cats (n = 21) and cats with inflammatory enteropathy (n = 13). Routine histopathology, immunohistochemistry (IHC), and qRT‐PCR were used to assess expression of MHC class II and to measure gene transcripts encoding the p35, p40, and p19 subunits of the IL‐12 family of cytokines and IFN‐γ.

Results

There were significant differences in expression of mRNA encoding IL‐12p35 and IL‐23p19 between healthy cats and cats with inflammatory enteropathy. IL‐12p35 mRNA was lower in the duodenal mucosa of cats with inflammatory enteropathy compared with the mucosa of healthy cats (P = .001). In contrast, IL‐23p19 mRNA expression was higher in duodenal biopsy specimens from cats with inflammatory enteropathy than in those from healthy controls (P = .001). There was no difference in expression of IL‐12p40 and IFN‐γ mRNA (P > .05). The majority of cats with inflammatory enteropathy had histologic evidence of moderate to severe colitis (score 2).

Conclusions and Clinical Importance

The results of this preliminary study suggest that IL‐23 plays a role in the pathogenesis of feline inflammatory enteropathy.

Mechanisms, causes, investigation and management of vomiting disorders in cats: a literature review

Vomiting is a common presenting complaint in feline practice. This article differs from previous reviews in that it is an evidence-based review of the mechanisms, causes, investigation and management of vomiting in the domestic cat. Published evidence was reviewed, and then used to make recommendations for clinical assessment, diagnosis, antiemetic drug treatment, dietary management and monitoring of cats presenting with vomiting. The strength of the evidence on which recommendations are made (and areas where evidence is lacking for cats) has been highlighted throughout.

Evaluation of fecal α1-proteinase inhibitor concentrations in cats with idiopathic inflammatory bowel disease and cats with gastrointestinal neoplasia

Idiopathic inflammatory bowel disease (IBD) and gastrointestinal lymphoma are common disorders in cats. The aim of this study was to evaluate fecal α(1)-PI concentrations, a marker of gastrointestinal protein loss, in cats with histopathological evidence of gastrointestinal inflammation or gastrointestinal neoplasia. Fecal and serum samples were obtained from 20 cats with chronic gastrointestinal disease in which endoscopic biopsies were performed. Two groups of cats were assembled based on histopathology: Group A (n = 8), mild to moderate IBD; Group B (n = 12), severe IBD or gastrointestinal neoplasia. Fecal α(1)-PI concentrations and serum concentrations of total protein, albumin, globulin, cobalamin, folate, pancreatic lipase immunoreactivity, and trypsin-like immunoreactivity were determined. Nineteen of the 20 diseased cats had elevated fecal α(1)-PI concentrations, ranging from 1.9 to 233.6 μg/g compared to 20 healthy control cats (normal range: ≤1.6 μg/g). Fecal α(1)-PI concentrations were statistically significantly different between healthy cats and cats of Group A (median: 3.9 μg/g, range: 1.3-9.2 μg/g, P < 0.001) or cats of Group B (median: 20.6 μg/g, 4.3-233.6 μg/g; P < 0.001), and between cats of Groups A and B (P < 0.01). Hypoalbuminemia, hypoproteinemia, and hypocobalaminemia were detected in 88%, 83%, and 56% of the diseased cats, respectively. This study suggests that increased fecal α(1)-PI concentrations in association with low serum albumin and total protein concentrations may be a common finding in cats with IBD or gastrointestinal neoplasia. Furthermore, fecal α(1)-PI concentrations appear to be higher in cats with severe IBD or confirmed gastrointestinal neoplasia when compared to cats with mild to moderate IBD.

Feline Idiopathic Inflammatory Bowel Disease

Practical relevance: Feline idiopathic inflammatory bowel disease (IBD) denotes one form of chronic enteropathy that is immunologically mediated and characterized by persistent or recurrent gastrointestinal (GI) signs and histologic inflammation. Signs of vomiting, diarrhea and weight loss generally predominate, and mucosal inflammation may occur in any portion of the GI tract (especially the small intestine). Affected cats may also have concurrent inflammation in other organs, such as the pancreas and liver, which may impact clinical disease severity.

Clinical challenges: The exact etiologies of this heterogeneous group of disorders have yet to be determined, though results from basic science and clinical studies suggest that interplay between genetic factors and enteric bacteria is crucial for disease development. The diagnosis is one of exclusion and requires intestinal mucosal biopsy to characterize the type and severity of the inflammatory infiltrate, and to differentiate IBD from other disorders, including alimentary lymphoma. Controversy exists concerning the relative diagnostic accuracy of endoscopic versus full-thickness specimens for the diagnosis of IBD and its differentiation from alimentary lymphoma.

Audience: This article is intended to provide veterinary practitioners with a comprehensive clinical update on idiopathic IBD in cats. It reviews the current evidence-based data, the diagnostic approach, the evolving histologic criteria, and treatment options and outcome for feline patients with this syndrome.

Pitfalls and progress in the diagnosis and management of canine inflammatory bowel disease

Inflammatory bowel disease (IBD) is the collective term for a group of chronic enteropathies characterized by persistent or recurrent gastrointestinal (GI) signs and inflammation of the GI tract. The specific steps that lead to IBD and the basis for phenotypic variation and unpredictable responses to treatment are not known. This article examines IBD in dogs, focusing on the interaction between genetic susceptibility and the enteric microenvironment (bacteria, diet), the utility of recently developed histologic criteria, the prognostic indicators, and the standardized approaches to treatment.

Numbers and distribution of immune cells in the tunica mucosa of the small and large intestine of full-thickness biopsies from healthy pet cats

In this study, CD3(+) T lymphocytes and IgA(+) , IgG(+) and IgM(+) plasma cells were quantified in the tunica mucosa of the intestinal tract of 12 pet cats without gastrointestinal diseases. The study included full-thickness biopsies of the duodenum, jejunum, ileum and colon. The distribution and quantification of CD3(+) T cells, IgA(+) , IgG(+) and IgM(+) plasma cells within the intestinal tunica mucosa was performed by using immunohistochemical methods and computer-aided morphometry. CD3(+) T cells were significantly prominent in the villi and their numbers increased from duodenum to ileum but decreased towards the colon. The predominant type of plasma cells was IgA(+) cells, followed by IgM(+) cells. The number of IgG(+) cells was generally low compared to the other plasma cell types investigated. The results of the vertical distribution showed that IgA(+) and IgM(+) plasma cells were most numerous in the lower crypt areas, whilst IgG(+) plasma cells accumulated in the upper crypt region with a decline towards the villi and the lower crypt areas of control cats. All types of plasma cells showed a general decline from the duodenum towards the caudal sections of the intestinal tract regarding the horizontal distribution of plasma cells. This study provides a comprehensive overview on the vertical and horizontal distribution and the number of CD3(+) T cells and IgA(+) , IgG(+) and IgM(+) plasma cells in the intestinal tunica mucosa of pet cats.

Idiopathic Inflammatory Bowel Disease in Cats: Rational Treatment Selection

Practical relevance Inflammatory bowel disease (IBD) is a common diagnosis in cats with chronic gastrointestinal signs. Its management presents clinical challenges, not least because rational therapy relies on a definitive diagnosis, and current understanding of the underlying pathogenesis has, to date, limited the development of specific therapies. The mainstays of treatment remain dietary manipulation and immunosuppressive therapy, but treatment failures are not uncommon. A logical clinical approach is important and there are a number of alternative or adjunctive treatments that can prove useful in refractory cases.

Evidence base This article draws on data from clinical trials in humans, in vitro studies, prospective and retrospective studies in cats with naturally occurring IBD, and clinical experience to discuss the work-up and treatment selection for cats with idiopathic IBD.

Patient group IBD affects young adult to geriatric cats of both sexes.

Audience Companion animal and feline practitioners are at the front line when it comes to managing these often challenging cases.

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.

Distribution of mast cell subtypes and immune cell populations in canine intestines: Evidence for age-related decline in T cells and macrophages and increase of IgA-positive plasma cells

The distribution and numbers of leucocytes and mast cells (MC) in the canine gastrointestinal tract of three different age groups was investigated immunhistochemically. In all age groups, CD3+ T cells were more prominent in the villus region than in the crypt areas without differences between intestinal segments, whereas macrophages were more randomly distributed. Kresylecht-violet and tryptase-positive MC were prominent in pericrypt regions with statistic significances. Chymase-bearing mast cells, IgA-, IgG- and IgM-containing cells did not show significant differences in their distribution but, except for IgG-positive cells, subjective trends with increasing numbers towards the crypts exist. The reasons for the distribution of T cells, macrophages, immunoglobulin-containing cells and mast cells are not clear. Lamina propria CD3+ T cells and macrophages significantly decreased whilst a significant increase of IgA-containing plasma cells with increasing age was found. For mast cell subtypes, IgG- and IgM-containing cells no significant changes in numbers with increasing age exist.

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.

The relationship of mucosal bacteria to duodenal histopathology, cytokine mRNA, and clinical disease activity in cats with inflammatory bowel disease

Feline inflammatory bowel disease (IBD) is the term applied to a group of poorly understood enteropathies that are considered a consequence of uncontrolled intestinal inflammation in response to a combination of elusive environmental, enteric microbial, and immunoregulatory factors in genetically susceptible cats. The present study sought to examine the relationship of mucosal bacteria to intestinal inflammation and clinical disease activity in cats with inflammatory bowel disease. Duodenal biopsies were collected from 27 cats: 17 undergoing diagnostic investigation of signs of gastrointestinal disease, and 10 healthy controls. Subjective duodenal histopathology ranged from normal (10), through mild (6), moderate (8), and severe (3) IBD. The number and spatial distribution of mucosal bacteria was determined by fluorescence in situ hybridization with probes to 16S rDNA. Mucosal inflammation was evaluated by objective histopathology and cytokine profiles of duodenal biopsies. The number of mucosa-associated Enterobacteriaceae was higher in cats with signs of gastrointestinal disease than healthy cats (P<0.001). Total numbers of mucosal bacteria were strongly associated with changes in mucosal architecture (P<0.001) and the density of cellular infiltrates, particularly macrophages (P<0.002) and CD3(+)lymphocytes (P<0.05). The number of Enterobacteriaceae, E. coli, and Clostridium spp. correlated with abnormalities in mucosal architecture (principally atrophy and fusion), upregulation of cytokine mRNA (particularly IL-1, -8 and -12), and the number of clinical signs exhibited by the affected cats. These data establish that the density and composition of the mucosal flora is related to the presence and severity of intestinal inflammation in cats and suggest that mucosal bacteria are involved in the etiopathogenesis of feline IBD.

Sustained generation of tissue dendritic cells from cats using organ stromal cell cultures

Currently most dendritic cells (DC) for in vitro study are generated from bone marrow or peripheral blood by culture in high concentrations of GM-CSF and other cytokines. However, in mice it is also possible to generate DC from spleen cells using long-term stromal cell cultures. To determine whether tissue DC could be also be generated from cats, we established stromal cell cultures from a number of different tissues of newborn cats. We found that stromal cell cultures from spleen, lung, liver, kidney, brain, and lymph node tissues were all capable of spontaneously generating DC over long periods of time (months), without requiring the addition of exogenous cytokines. The tissue DC generated from these stromal cell cultures could be readily isolated at high purity by simple mechanical detachment. The feline tissue DC expressed high levels of CD11c, CD11b, and MHC Class II and variable levels of CD80 and CD14 and exhibited high levels of spontaneous macropinocytosis. Moreover, DC from spleen stromal cell cultures, but not DC from lung or liver stromal cell cultures, stimulated mixed-lymphocyte reactions. The DC generated from the stromal cell cultures were relatively independent of GM-CSF for survival and proliferation, indicative of a dependence on other growth factors produced by the stromal cells. These results suggest that tissues of young cats contain a population of resident DC progenitor cells that under appropriate conditions are capable of spontaneous proliferation and generation of immature DC.

Measurement of cytokine mRNA expression in intestinal biopsies of cats with inflammatory enteropathy using quantitative real-time RT-PCR

Inflammatory bowel disease (IBD) is a common condition in cats characterised by infiltration of inflammatory cells into the intestinal mucosa. In this study, real-time reverse transcriptase polymerase chain reaction (RT-PCR) was used to quantify cytokine messenger RNA (mRNA) expression in intestinal biopsies from cats. Biopsies were collected from seven cats with chronic diarrhoea and histologically confirmed IBD, five cats with chronic diarrhoea due to non-IBD gastrointestinal (GI) disease, and nine clinically normal cats with or without subclinical inflammatory changes in small intestine. Real-time RT-PCR was developed for quantification of mRNA encoding interleukin (IL)-2, IL-4, IL-5, IL-6, IL-10, IL-12 (p35 and p40), IL-18, tumour necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma) and transforming growth factor-beta (TGF-beta). Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was used as a 'housekeeper' gene. All real-time PCR efficiencies were>90% (range 90.4-102%) with correlation coefficients >0.99 (range 0.998-1). The results of the study were analyzed on the basis of either clinical presentation or histopathological evidence of intestinal inflammation. The former analysis showed that mRNA encoding IL-10 and TGF-beta (immunoregulatory cytokines), and IL-6, IL-18, TNF-alpha and IL-12 p40 (Th1 and pro-inflammatory cytokines) was significantly higher in clinically normal cats and cats with IBD when compared to cats with other GI diseases. IL-5 mRNA was significantly higher in cats with IBD compared to clinically normal cats. IL-2 mRNA was significantly lower in cats with non-IBD GI disease than in clinically normal cats. Analysis on the basis of histopathological change revealed that cats with intestinal inflammation had significantly more transcription of genes encoding IL-6, IL-10, IL-12p40, TNF-alpha and TGF-beta than those with normal intestinal morphology. The results suggest that immune dysregulation plays a role in feline IBD and that IBD in cats has a complicated pathogenesis with both pro-inflammatory and immunoregulatory features.

The postnatal development of the mucosal immune system and mucosal tolerance in domestic animals

The mucosal immune system is exposed to a range of antigens associated with pathogens, to which it must mount active immune responses. However, it is also exposed to a large number of harmless antigens associated with food and with commensal microbial flora, to which expression of active, inflammatory immune responses to these antigens is undesirable. The mucosal immune system must contain machinery capable of evaluating the antigens to which it is exposed and mounting appropriate effector or regulatory responses. Since the immune system is likely to have evolved initially in mucosal tissues, the requirement to prevent damaging allergic responses must be at least as old as the adaptive immune system, and studies of the mechanisms should include a range of non-mammalian species. Despite the importance for rational design of vaccines and for control of allergic reactions, the mechanisms involved are still largely unclear. It is not clear that the classical experimental protocol of "oral tolerance" is, in fact, measuring a biologically important phenomenon, nor is it clear whether tolerance is regulated in the evolutionarily recent organised lymphoid tissue (the lymph nodes) or the more ancient, diffuse architecture in the intestine. The capacity of the immune system to discriminate between "dangerous" and "harmless" antigens appears to develop with age and exposure to microbial flora. Thus, the ability of an individual or a group of animals to correctly regulate mucosal immune responses will depend on age, genetics and on their microbial environment and history. Attempts to manipulate the mucosal immune system towards active immune responses by oral vaccines, or towards oral tolerance, are likely to be confounded by environmentally-induced variability between individuals and between groups of animals.

Mucosal defence along the gastrointestinal tract of cats and dogs

Diseases that are associated with infections or allergic reactions in the gastrointestinal and respiratory tracts are major causes of morbidity in both cats and dogs. Future strategies for the control of these conditions require a greater understanding of the cellular and molecular mechanisms involved in the induction and regulation of responses at the mucosal surfaces. Historically, the majority of the fundamental studies have been carried out in rodents or with tissues obtained from man, but the expanding range of reagents available for the study of farm and companion animals provides opportunities for study in a wider range of animals including cats and dogs. To date, these studies have tended to be focussed on characterising the cellular distributions in healthy animals and in groups of cats and dogs identified as having an increased risk of mucosal disturbance. Where species comparisons of mucosal immune systems have been made, the results have tended to be divided between monogastric and ruminant animals. It is then not surprising that the mucosal immune systems of both cats and dogs bear greatest similarity to that documented for man and pigs. For example, IgA is the dominant immunoglobulin in mucosal secretions of cats and dogs and oral tolerance can be induced following the introduction of novel antigens into the diet. Also like several other species, cats become transiently hypersensitive to the newly introduced dietary antigen prior to the establishment of tolerance. In contrast, there are a number of potentially important differences. In particular, there are significant differences between cats and dogs in the expression MHC class II molecules on gut epithelial cells. Similarly, it has been reported that cats have elevated numbers of intraepithelial lymphocytes (IEL) and that a proportion of these express surface IgM. It remains to be determined if these differences reflect the way in which the animals are maintained and if they may have greater biological significance.

Antigen presenting cells in mucosal sites of veterinary species

The ability of antigen presenting cells, in particular dendritic cells, to integrate a variety of environmental signals, together with their ability to respond appropriately by initiating either tolerance or defensive immune responses make them cells of particular relevance and importance in the mucosal environment. They have been demonstrated in a variety of mucosal tissues in veterinary species and have been characterized to varying degrees, showing that fundamental immunological principles apply throughout all species, but also highlighting some species differences. A major advantage of carrying out immunological research in veterinary species is their size: it is possible to cannulate lymphatic ducts and obtain information about cell migration between different tissues. It is also possible to obtain pure populations of relatively rare cell types such as the plasmacytoid dendritic cells or mucosal dendritic cells ex vivo for the study of immune responses to diseases in their natural host and for other thorough functional studies. Two major myeloid antigen presenting cell (APC) (dendritic cells, DC) cell populations have been described in gut draining lymph and other mucosal sites in ruminants and pigs, characterised by the presence or absence of surface molecules, their enzyme profiles, their ability to phagocytose and their different potential as APC. There is evidence that one of these subsets has migrated from the diffuse mucosal tissue, where it is found as a phagocytic as well as stimulatory APC population, which in turn may be derived from blood macrophages. In addition, the presence and role in viral infection of the IFN-alpha producing plasmacytoid DC in mucosal tissue is discussed, based on studies in pigs.

Immunohistochemical Diagnosis of Alimentary Lymphomas and Severe Intestinal Inflammation in Cats

Intestinal tissue samples were examined from 32 cats in which a histopathological diagnosis of alimentary lymphoma or multicentric lymphoma affecting the gastrointestinal tract had been made. These samples were re-evaluated histopathologically and serial sections were examined immunohistochemically with antisera specific for the lymphoid markers CD3, CD79a and BLA-36 and for class II molecules of the major histocompatability complex. The cats ranged in age from 4-16 years (median 10.5 years). The main presenting clinical signs were vomiting, diarrhoea and weight loss. The majority of alimentary lymphomas were of the B-cell type (n=15), whereas cases of T-cell lymphoma were fewer in number (n=8). Four cats had lymphoma of a mixed T-and B-cell phenotype. In five of the cats, immunohistochemistry suggested an inflammatory process, in contradiction to the original histopathological diagnosis of lymphoma. Immunolabelling would appear to be a useful adjunct to histopathology in classifying cases of feline alimentary lymphoma, and may help in distinguishing lymphoma from severe intestinal inflammation.