Journal of clinical immunology
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To explore possible mechanisms for the association between elevated immunoglobulin levels and lower pulmonary function in cystic fibrosis patients, we measured serum IgG subclass levels and anti-P. aeruginosa IgG subclass titers and correlated levels with neutrophil phagocytosis and chemotaxis. Serum was obtained from 13 cystic fibrosis patients colonized with the same serotype of P. aeruginosa, 12 noncolonized patients, and 12 normal volunteers. All anti-P. aeruginosa IgG subclass titers were elevated in serum from colonized patients. ⋯ Chemotactic index directly correlated with anti-P. aeruginosa IgG3 titer and serum IgG3. These data demonstrate that cystic fibrosis patients with increased IgG3 levels are in poorer clinical condition and that their serum enhances neutrophil function. Such patients may have increased pulmonary inflammation with subsequent lung damage.