Idiopathic eosinophilic esophagitis is associated with a TH2-type allergic inflammatory response

Background: Idiopathic eosinophilic esophagitis (IEE) is a chronic-inflammatory disorder of the esophagus of unknown origin. The established cornerstone of diagnosis is a dense infiltration of the esophagus with eosinophils, but neither the precise pattern of inflammatory cell infiltration nor the mechanisms that likely contribute to induction and maintenance of the inflammatory response have been described. Objective: The intention of this study was to characterize the esophageal inflammatory infiltrate and the expression of cytokines in the esophagus in this disease. In addition, we searched for immunologic abnormalities of blood leukocytes to exclude major primary hyporeactive and hyperreactive conditions of the immune system. Methods: Infiltration of inflammatory cells in the esophagus, stomach, and duodenum was analyzed by immunohistochemistry through use of mAbs against lineage-associated molecules. Cytokine expression was measured by ELISA and immunohistochemical analysis. Lymphocyte subpopulations in blood were determined by means of flow cytometry. Results: High eosinophil infiltration into the esophageal squamous epithelium was observed in patients with IEE but not in control subjects. Interestingly, increased T-cell and mast cell numbers were also found within the epithelium in these patients. In contrast, the numbers of inflammatory cells were not increased in the stomach and duodenum in patients with IEE, suggesting a specific inflammatory process within the esophagus. Moreover, increased expression of IL-5 and TNF-alpha was observed in esophageal epithelial biopsy specimens. The distribution of lymphocyte subsets in the peripheral blood and their capacity to generate cytokines did not reflect the changes observed at the inflammatory site. Conclusions: IEE is a selective inflammatory response of the esophagus. T cells, IL-5, eosinophils, and IgE-mediated mechanisms appear to be involved, giving rise to the possibility that allergic reactions might play a role in the pathogenesis of the disease.