Immunofluorescence studies of lung tissue in cystic fibrosis

Previous studies have suggested that immune mechanisms contribute to lung injury in cystic fibrosis (CF); however, there have been no comprehensive studies of immunofluorescent staining patterns in CF lung tissue. We performed immunofluorescence (IF) studies for immunoglobulins, C3, and fibrinogen on autopsy frozen lung tissue from 21 CF patients. Results were compared with lung findings in patients without CF. In CF-derived lung tissue fibrinogen was ubiquitous along the alveolar wall, alveolar space, and interstitium. Free immunoglobulin G (IgG) and IgA coated the alveolar surface segmentally in 14 and 6 cases, respectively. Unequivocal interstitial deposits were infrequent and IgM was present in blood vessels in one patient only. Intra-alveolar and interstitial inflammatory cells demonstrated cytoplasmic IgG, IgA, and IgM, respectively, in 18, 14, and 6 patients. C3 was seen only segmentally along the alveolar wall in two patients and in blood vessels in one. Antinuclear antibody (ANA) staining of interstitial cells for C3 and immunoglobulins was seen in five patients, four of whom had interstitial pneumonitis. Insignificant amounts of alveolar or interstitial fibrinogen and immunoglobulins in inflammatory cells were seen in controls in the absence of lung inflammation. The IF patterns were similar in the inflammatory lesions of CF and control specimens. The IF patterns observed in CF lung tissue are consistent with nonspecific vascular leakage and chronic inflammation with little evidence of immune complex deposition in the interstitium or blood vessels. This study confirms previous reports of ANA activity in CF patients, although the significance of this finding is unknown.