CROSS-SECTIONAL AND LONGITUDINAL-STUDIES OF NATURALLY-OCCURRING ANTIBODIES TO PSEUDOMONAS-AERUGINOSA IN CYSTIC-FIBROSIS INDICATE ABSENCE OFANTIBODY-MEDIATED PROTECTION AND DECLINE IN OPSONIC QUALITY AFTER INFECTION

Most patients with cystic fibrosis (CF) develop chronic endobronchial infection with mucoid Pseudomonas aeruginosa, It has been suggested th at opsonic antibodies to the mucoid exopolysaccharide of P. aeruginosa protect older CF patients (>12 years of age) who have remained free o f colonization by this organism, Serum antibodies from chronically inf ected CF patients had greater total complement-dependent opsonic activ ity than did those of older noncolonized patients (P < .02), but when bound antibody was equalized, opsonic quality was greater for the latt er group (P < .03), In longitudinal studies, antibody titers to mucoid P. aeruginosa rose greatly after initial infection, but opsonic quali ty declined (P = .002), Twenty CF patients who passed age 12 free of P . aeruginosa colonization developed chronic P. aeruginosa lung infecti on at ages 14-35 years, Thus, naturally occurring antibodies do not pr otect CF patients from P. aeruginosa infection, and opsonic quality of serum antibodies deteriorates as infection becomes established.