Immunoglobulins and albumin in sputum from patients with cystic fibrosis. A study of protein stability and presence of proteases

Sputum sol phase from seventeen cystic fibrosis (CF) patients chronically infected in the lungs with mucoid Pseudomonas aeruginosa and presenting multiple precipitins in serum against this bacterium (CF + P) and 11 CF patients without P. aeruginosa infection (CF-P) were examined for proteolytic activity in a fibrin plate assay. The proteolytic activity was significantly higher (p smaller than 0.02) in sputum from CF + P patients than in sputum from CF-patients. This difference was only quantitative since sputum sol phase from both groups degraded fibrinogen to non-precipitable material. The proteolytic degradation of IgG, IgA, secretory IgA and albumin in the sputum sol phases was investigated by means of gel filtration and the stability of these proteins during various storage conditions was examined. Degradation of IgG, IgA, secretory IgA and albumin in the sputa was not demonstrable and the proteins were stable for at least 4 weeks at 4 degree C.