ORIGINAL ARTICLE Cellular Localization of Interleukin 13 Receptor α2 in Human Primary

Background: Interleukin (IL) 13 is a key cytokine in asthma, regulating fi brosis, airway remodeling, induction of immunoglobulin E synthesis by B cells, bronchial hyperresponsiveness, and mucus production. IL-13 signals through the type II IL-4 receptor (IL-4R), which is composed of the IL-4Rα and the IL-13Rα1 chains. Another IL-13 binding chain, IL-13Rα2, binds IL-13 with high affi nity but has no known signaling capability and is thought to serve as a decoy receptor providing tight regulation of IL-13 responses. Methods: In this study, we investigated the cellular localization of IL-13Rα2 in human primary bronchial epithelial cells and fi broblasts using fl ow cytometry and confocal microscopy, as well as the in vivo expression of IL-13Rα2 in the human bronchial mucosa by means of immunohistochemistry. Results: IL-13Rα2 is predominantly an intracellular rather than a membrane-bound molecule in both human primary bronchial epithelial cells and fi broblasts and displays a diffuse granular cytoplasmic distribution in both cell types. IL-13Rα2 protein is expressed in vivo in the human bronchial mucosa with its expression being higher in bronchial epithelial cells than bronchial fi broblasts both in vivo and in vitro. Conclusions: IL-13Rα2 is expressed by both human primary bronchial epithelial cells and fi broblasts as an intracellular protein with a diffuse cytoplasmic distribution. In vivo, IL-13Rα2 is expressed in the human airway mucosa mainly by bronchial epithelial cells. Key words: IL-13 receptor α2. Intracellular protein. Cellular localization. Cytoplasmic compartment. Bronchial epithelial cells. Bronchia