Inflammation is a complex problem in cystic fibrosis and to date no specific markers are available. The inflammatory response is a multicellular event that involves blood, vascular and epithelial cells. One way these cells respond to an infectious/inflammatory agent is to release small vesicles, termed microvesicles (MV). More the cells become activated by these agents more MV they release that can be counted in the blood. Researchers will use flow cytometry to count simultaneously the number of circulating platelet, leukocyte, endothelial and epithelial MV in 20 CF patients with varying genotype and degree of inflammatory lung disease. Patients will be examined every 3 months for 21 months and re-examined at the beginning and the end of any exacerbation and laboratory markers will be correlated with standard clinical parameters. The main objectives of the project are to validate the integrated analysis of circulating MV as a new biomarker of CF lung disease progression and response to therapy; and to develop a new diagnostic/prognostic laboratory tool for CF, readily transferable to the clinic.