ANTI-PSEUDOMONAS-AERUGINOSA IGG SUBCLASS TITERS IN PATIENTS WITH CYSTIC-FIBROSIS - CORRELATIONS WITH PULMONARY-FUNCTION, NEUTROPHIL CHEMOTAXIS, AND PHAGOCYTOSIS

To explore possible mechanisms for the association between elevated im munoglobulin levels and lower pulmonary function in cystic fibrosis pa tients, we measured serum IgG subclass levels and anti-P. aeruginosa I gG subclass titers and correlated levels with neutrophil phagocytosis and chemotaxis. Serum was obtained from 13 cystic fibrosis patients co lonized with the same serotype of P. aeruginosa, 12 noncolonized patie nts, and 12 normal volunteers. All anti-P. aeruginosa IgG subclass tit ers were elevated in serum from colonized patients. IgG3 level and ant i-P. aeruginosa IgG3 titer were inversely correlated with pulmonary fu nction. Phagocytosis of P. aeruginosa by neutrophils correlated with s erum IgG3 level and was increased by opsonization with serum from colo nized patients. Chemotactic index was increased in serum from colonize d patients and inversely correlated with pulmonary function chest roen tgenogram score. Chemotactic index directly correlated with anti-P. ae ruginosa IgG3 titer and serum IgG3. These data demonstrate that cystic fibrosis patients with increased IgG3 levels are in poorer clinical c ondition and that their serum enhances neutrophil function. Such patie nts may have increased pulmonary inflammation with subsequent lung dam age.