Intraepithelial eosinophils are a type of white blood cell, called an eosinophil, found within the epithelial lining of body tissues. The epithelium forms the protective surface layers of organs like the digestive tract or respiratory passages. Their presence in this specific tissue location often signals an underlying issue. The term “intraepithelial” means “within the epithelium.”
Eosinophils and Their Normal Role
Eosinophils are a type of white blood cell that plays a part in the immune system. These cells originate in the bone marrow, circulate in the bloodstream, and then settle in tissues, especially in the respiratory and digestive systems. They contain granules that stain brick-red with eosin dye.
Eosinophils primarily defend the body against multicellular parasites like worms. They also participate in allergic reactions and asthma, where their activity can contribute to inflammation. Eosinophils contain secretory granules filled with enzymes and proteins that can destroy pathogens, but this activity can also lead to tissue inflammation and damage. While present in many tissues, eosinophils are typically found in very low numbers or are absent from the epithelial lining of certain organs, such as the esophagus, in healthy individuals. Their presence in these epithelial locations, particularly in higher concentrations, often suggests an underlying immune response or condition.
When Intraepithelial Eosinophils Become a Concern
An elevated presence of intraepithelial eosinophils signals inflammation or an immune-mediated condition. The accumulation of these cells in the epithelial lining indicates an ongoing immune response within that tissue. Eosinophils release chemical mediators, including enzymes like eosinophil peroxidase and major basic protein, which can be toxic to both pathogens and host tissues. This release contributes to tissue damage and inflammation.
When eosinophils accumulate in higher numbers within epithelial tissues, it suggests the body is reacting to a perceived threat, such as an allergen or an infection. This increased presence can lead to localized tissue injury and dysfunction. For example, in the esophagus, even a small number of intraepithelial eosinophils can indicate prolonged acid reflux. The sustained presence of these cells can also contribute to tissue remodeling, such as fibrosis, which can affect organ function.
Common Conditions Associated with Elevated Intraepithelial Eosinophils
Elevated intraepithelial eosinophils are a defining characteristic of several conditions, with Eosinophilic Esophagitis (EoE) being a prominent example. EoE is a chronic, immune-mediated inflammatory disease of the esophagus, often triggered by food or environmental allergens. Individuals with EoE commonly experience symptoms such as difficulty swallowing (dysphagia), food impaction, and heartburn. This condition is specifically diagnosed by the presence of 15 or more eosinophils per high-power field in esophageal biopsy specimens.
Beyond EoE, other gastrointestinal conditions can also present with increased intraepithelial eosinophils. Eosinophilic gastroenteritis, for instance, involves eosinophil infiltration in other parts of the digestive tract, such as the stomach or small intestine, leading to symptoms like abdominal pain, nausea, vomiting, and diarrhea. Celiac disease, an autoimmune disorder triggered by gluten, may also show increased intraepithelial eosinophils in the small intestine, though this is usually accompanied by other characteristic changes in the intestinal lining. Certain forms of inflammatory bowel disease can sometimes show elevated eosinophils.
Diagnosis and Management
The identification of elevated intraepithelial eosinophils involves an endoscopic procedure. A thin, flexible tube with a camera is inserted to visualize the internal lining of an organ, and small tissue samples (biopsies) are collected. These biopsies are sent to a pathologist for microscopic examination, who counts the eosinophils within the epithelial tissue to determine if their presence is elevated.
Management strategies for conditions with elevated intraepithelial eosinophils depend on the underlying diagnosis. For conditions like Eosinophilic Esophagitis, common approaches include dietary modifications, such as elimination diets to avoid food allergens. Medications, including swallowed topical corticosteroids (which reduce inflammation directly in the esophagus) or proton pump inhibitors (which reduce stomach acid), may also be prescribed. Ongoing monitoring through repeat endoscopies and biopsies is often necessary to assess treatment effectiveness and disease progression.