The cross-sectional comparison examined bronchoalveolar lavage, high resolution, thin-section computer tomography (HRCT), neutrophil or monocyte labeled scintigraphy). The serial, longitudinal evaluation monitored the progression of disease. The study of PSS patients, without disease or with subclinical disease, was particularly useful because it allowed examination of the early events in the pathogenesis of IPF. The long-term goal of the project was to determine what alterations in cellular composition, function and trafficking occurred in the lung parenchyma of patients with IPF and to relate these alterations to the disease stage, prognosis, and therapeutic responsiveness.