Complement activation and pulmonary inflammation in CF patients.

This study examined whether biologic activation of C3 with subsequent pulmonary inflammation 
takes place in the lungs of patients with cystic fibrosis. Plasma 
complement C3 levels were all normal. Eleven of the patients with 
the C3 split product C3c were from the group of 14 
patients suffering from chronic infection with mucoid strains of Pseudomonas aeruginosa 
and 2 were from the group of 14 CF patients without 
P. aeruginosa infection. This difference was significant (p < 0.002). A 
comparison of albumin ratios between the 13 patients with the C3 
split product C3c and the remaining other 15 patients showed a 
significant higher ratio in the former group (p < 0.01) on 
an average 4.1 versus 1.4 per cent. The significantly higher albumin 
ratio demonstrated in the patients with C3c in their sputum sol 
phase supports the concept of complement-induced inflammation with subsequent transudation of 
plasma proteins in these patients. This study thus shows that complement-mediated 
inflammatory reactions may play an important role in the pathogenesis of 
pulmonary tissue damage in patients with CF, even when the plasma 
C3 levels are normal, and it supports the concept of chronic 
P. aeruginosa lung infection as an immune complex disease in CF 
patients. 