School of Medicine

Although our understanding of the pathogenesis of asthma remains limited, data now indicate that most patients with asthma have an immune-mediated component. Allergic asthma is thought to involve a response to a specific antigen that triggers a specific adaptive immune response in the lung that requires time. However, new data also implicate the innate immune response, either in concert with or independent of the adaptive response. The broad goal of this project was to explore the role that the cytokine interleukin (IL) 33 and its receptor, ST2, may play in asthma. The first objective was to explore the role of ST2 in a mouse model of asthma in which ovalbumin is used to induce airway hyperresponsiveness and inflammation. We hypothesized that ovalbumin-challenged mice would show increased expression of ST2 compared to unchallenged mice. The second objective was to characterize the stimuli for expression and release of IL-33 from the human airway epithelium using the human airway epithelial cell line BEAS-2B. We hypothesized that IL-33 auto-regulates its expression in airway epithelial cells. By Western blot, we found that expression of the soluble form of ST2 (sST2) appeared higher in lung tissue from ovalbumin-challenged mice compared to lung tissue from control mice. Similarly, by immunohistochemistry, we found higher expression of ST2 in lung tissue of ovalbumin-challenged mice compared to controls. Staining with mouse anti-ST2 antibody also showed ST2 expression in mediastinal lymph node tissue from ovalbumin-challenged mice. By flow cytometry, we found that splenic tissue from ovalbumin-challenged mice had a higher proportion of CD4+ cells that expressed ST2 on the cell surface (CD4+ST2+ cells) compared to control mice. We then studied BEAS-2B cells that had been conditioned with 10 ng/ml of human recombinant IL-33 in growth media or growth media alone for 24 hours at 37°C. However, our results from RT-PCR and ELISA showed that BEAS-2B cells did not express significant IL- 33 with or without IL-33 con.