Interleukin 3, granulocyte-macrophage colony-stimulating factor, and interleukin 5 in eosinophilic gastroenteritis

Background & Aims: Eosinophilic gastroenteritis (EG) is characterized by an eosinophilic infiltration of the gastrointestinal tract. The mechanism for the intestinal recruitment of eosinophils in EG remains unknown. Eosinophil recruitment and activation is induced by three main cytokines: interleukin (IL) 3, granulocyte-macrophage colony-stimulating factor (GM-CSF), and IL-5. The aim of this study was to examine the immunoreactivity for IL-3, GM-CSF, and IL-5 within the duodenal and colonic mucosa of 10 patients with EG. Methods: Endoscopic biopsy specimens were obtained from 10 patients with 50 and 10 controls. IL-3, GM-CSF, and IL-5 was evaluated by immunohistochemistry. Electron microscopy combined with immunogold staining was used to identify the labeled cells and to localize these growth factors ultrastructurally. Results: A significant increase in the number of eosinophils was found in both duodenal and colonic mucosa from all 10 patients with EG compared with controls. In the same tissue, immunohistochemistry detected IL-3, GM-CSF, and IL-5 in 9 of 10 patients with EG. The one exception had received treatment with steroids. These cytokines were not detected in the control group. Ultrastructurally, IL-3, GM-CSF, and IL-5 were localized in the granule matrix of eosinophils. Conclusions: The release of these cytokines with autocrine and/or paracrine activities by eosinophils may be involved in the persistence of intestinal eosinophil infiltration.