Complement in cystic fibrosis.

Complement components C3, C4, and C3A were estimated in 30 patients with 
cystic fibrosis aged 1 to 21 years (M:F = 16:14) and 
were compared with results in 40 healthy, age-matched subjects. The influences 
of the clinical score, sputum microbiology, and the patients' sex were 
also investigated. In contrast to most previous communications, this paper shows 
that, compared to the control group, a significant decrease of C3 
(P less than 0.001) and C4 (P less than 0.02) was 
observed whereas C3A levels were not altered. There were no increases 
in complement. Shwachman-scores above or below 70 did not influence the 
complement levels, nor did exacerbations of the disease change the levels. 
No influence of the patients' sex could be shown. Pseudomonas aer. 
in the sputum was clearly associated with complement defects (14/18). Alternative-pathway 
involvement of complement activation could be demonstrated in 32%. The results 
make complement activation due to pulmonary infection most likely. The defects 
observed probably represent secondary changes. 