Activated complement in the sputum from patients with cystic fibrosis.

14 cystic fibrosis (CF) patients chronically infected with mucoid P. aeruginosa and presenting multiple precipitins in serum against this bacterium (CF + P) and 13 CF patients without P. aeruginosa infection (CF-P) had their plasma and sputum sol phase examined for albumin, Clq. C3/C3c, C4 and C5 by means of electroimmunoassays. Their sputum sol phase was examined also for factor B by rocketimmunoelectrophoresis. C3c was demonstrated in the sputum sol phase but significantly more frequent (p less than 0.01) among the CF + P patients than among the CF-P patients. Factor B was also demonstrated in the sputum sol phase, but no significant difference in frequency could be demonstrated between the CF + P and the CF-P patients. None of the results indicated that a local pulmonary production of complement factors took place. Complement activation was significantly (p less than 0.01) associated with inflammation expressed as increased (formula: see text). The results show the importance of complement mediated inflammation in the pathogenesis of pulmonary tissue damage in patients with CF and support the concept of chronic P. aeruginosa lung infection as an immune complex disease in CF patients.