Department of Veterinary and Biomedical Sciences
Dr. Srirama Rao
White Blood Cell Enzyme Holds Key to Monitoring Inflammatory Bowel Disease
Eosinophilic enteritis (EE) is the second most frequently diagnosed form of inflammatory bowel disease (IBD) in dogs. It is characterized by an increased number of white blood cells known as eosinophils in the intestinal mucosa. We, in collaboration with researchers from the Departments of Veterinary Population Medicine and Veterinary Clinical Sciences, have used a method based on detecting a protein specifically expressed by eosinophils to efficiently evaluate and quantitate the presence of these cells in gastrointestinal (GI) biopsies. This technique may serve as a potential marker for diagnosis and treatment of IBD in dogs.
From the Scientist:
Inflammatory bowel disease (IBD) in companion animals occurs as a persistent or recurrent gastrointestinal (GI) inflammation in the absence of other underlying causes, such as infection or cancer. Eosinophilic enteritis (EE) is the second most common form of IBD in dogs and is characterized by the presence of infiltrating eosinophils in the intestinal mucosa along with other clinical signs, including diarrhea, weight loss and abdominal pain. The conventional staining method used to identify eosinophils in the intestinal mucosa detects intact cells but not cells that have released inflammation-promoting mediators (degranulated) and are contributing to bowel inflammation.
In the current study, we investigated the ability of a monoclonal antibody against eosinophil peroxidase (EPX), an intracellular enzyme expressed specifically by eosinophils, to efficiently detect and enumerate tissue-infiltrating intact and degranulated eosinophils in the small intestine of dogs with IBD. We used specimens collected at necropsy from dogs with IBD that were either untreated or given an anti-inflammatory drug. Intestinal specimens from dogs having no clinical evidence of GI disease and thus had received no treatment served as a control group. Immunoreactivity to EPX was observed in intestinal tissues as a prominent dark reddish-brown staining pattern that allowed easy and reliable identification of intact and degranulated eosinophils (see Figure, Panel A, conventional hematoxylin-eosin staining, Panel B, EPX staining [red arrow: degranulated eosinophil, black arrow: intact eosinophil]; Scale Bar = 200 µm). Both intact and degranulated (i.e. activated) eosinophils were more prevalent in the upper small intestine of untreated dogs with IBD compared to tissues from dogs with IBD that received drug treatment or unaffected dogs that served as the control group. This study demonstrates the utility of using EPX monoclonal antibody-based staining as a strategy for the quantitative assessment of eosinophils (intact and degranulated) in small intestinal biopsies from dogs with IBD. Overall, this new technique may serve as a potential diagnostic tool to reliably identify IBD, monitor the progression of this disease, and evaluate the effectiveness of treatment in canine patients.
by Savita Rao