Eosinophil integrins: interactions with VCAM and fibronectin

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(Applicant's Abstract) Eosinophils (EOS) preferentially accumulate in the airways of patients with asthma and contribute to airway hyperresponsiveness and airflow obstruction. The mechanisms for selective recuitment of EOS in asthma likely include: (a) priming of circulating EOS; (b) local upregulation of vascular cell adhesion molecule-1 (VCAM) by IL-4 and IL-13 Th-2 cytokines; (c) rolling and arrest of primed circulating EOS on VCAM-expressing pulmonary endothelial cells; (d) migration of arrested EOS into tissues in response to chemokines or other agonists of G-protein coupled receptors (GPCRs); (e) yet-to-be-defined chemotactic, chemokinetic, and chemostatic events in which EOS interact with VCAM and fibronectin (FN) in the bronchial wall; (f) movement of EOS into the airway lumen; and (g) prolonged survival of EOS of the airway wall and lumen driven by GM-CSF. EOS express 2 integrins that interact with VCAM and FN, alpha4beta1 and alpha4beta7, and a third, alphaDbeta2, that interacts with VCAM but not FN. VCAM and FN each exist as several differentially spliced forms. We hypothesize that the splice variations change the specificities and valencies of VCAM and FN for integrins on EOS and hence the responses of EOS to integrin ligation. Our aims are twofold. First, we will establish how interactions of alpha4beta1, alpha4beta7, and alphaDbeta2 with differentially spliced forms of VCAM and FN regulate adhesion, migration, and viability of EOS. Second, we will determine the distribution of various forms of VCAM and FN in normal and asthmatic airways. To accomplish these aims, we will (1) express differentially spliced forms of VCAM and FN that likely are encountered by EOS in transit from blood to airway; (2) prepare cell lines that replicate the expression patterns of integrins on blood and airway EOS and serve as models for EOS obtained from the circulation and lung before and after an asthma exacerbation; (3) characterize the abilities of blood EOS, airway EOS, and model cells to interact with splice forms of VCAM and FN in binding, adhesion, migration, and survival assays; (4) characterize the effects of cytokines and GPCR agonists on integrin-ligand interactions; and (5) prepare monoclonal antibodies to differentially spliced forms of VCAM and FN and determine distribution in normal and asthmatic lung.