HIGH-LEVELS OF COMPLEMENT-ACTIVATION CAPACITY IN SERA FROM PATIENTS WITH CYSTIC-FIBROSIS CORRELATE WITH HIGH-LEVELS OF IGG3 ANTIBODIES TO PSEUDOMONAS-AERUGINOSA ANTIGENS AND POOR LUNG-FUNCTION

Heat-stable opsonins from sera of cystic fibrosis (CF) patients were i nvestigated for their ability to activate complement. Complement activ ation by Pseudomonas aeruginosa after opsonization with patient serum was examined in a complement-consumption assay. Absorption of patients ' sera with formalin-treated and boiled bacteria removed specific anti bodies and the complement activation decreased. We found a positive co rrelation between serum complement-activation ability and IgG3 antibod y levels to lipopolysaccharide (LPS), alginate, and a crude mixture of P. aeruginosa antigens (sonicate) in a group of patients with high le vels of anti-Pseudomonas precipitins. In the same group of patients a significant negative correlation was found between complement activati on and lung function. Eighteen patients have been followed longitudina lly with serum samples covering the pre-infection, the early, and the late stages of chronic infection. Patients with poor lung function sho wed significantly higher levels of complement-activation capacity. We conclude that patients with high levels of specific IgG3 antibodies ar e able to induce a high level of complement activation and then develo p more aggressive pulmonary tissue damage, probably secondary to local immune complex formation. (C) 1995 Wiley-Liss, Inc.