Immune complexes in the sputum of patients with cystic fibrosis suffering from chronic Pseudomonas aeruginosa lung infection

12 cystic fibrosis (CF) patients chronically infected with mucoid P. aeruginosa and presenting multiple precipitins in serum against this bacterium and 12 patients without P. aeruginosa infection were examined for occurrence of soluble immune complexes in their sputum sol phase by a complement consumption assay and a solid phase rheumatoid factor binding assay. The correlation between the results obtained in the two assays was significant (r = 0.625, p less than 0.01). The patients chronically infected with P. aeruginosa showed a significantly (p less than 0.01) higher frequency of immune complex activity in their sputum sol phase, as compared to the patients without P. aeruginosa lung infection. These findings point to the possibility that chronic lung infection with mucoid P. aeruginosa in CF may be an immune complex disease.