Combined evaluation of circulating immune complexes and antibodies toPseudomonas aeruginosa as an immunologic profile in relation to pulmonary function in cystic fibrosis

We developed a solid-phase radioimmunoassay with a reference standard pseudomonas antigen and used this with¹²⁵I-labeled anti-human immunoglobulin to evaluate specific antibodies toPseudomonas aeruginosa, qualitatively and quantitatively, in sera from children with cystic fibrosis (CF) whose lungs were colonized by this bacterium. The results of this IgG assay correlated with the number of precipitin antibodies to the standard reference antigen determined by cross-immunoelectrophoresis in the same sera. Forced expiratory volume (FEV₁; percentage predicted), determined as an indicator of lung injury in CF, was evaluated as an immunologic response to pseudomonas, against a profile derived from combined serial data on both the circulating immune complexes (CIC) and thePs. aeruginosa antibodies (N=25 CF patients; 108 sera). This revealed that in CF patients who had no specific IgG antibodies toPs. aeruginosa and no IgG-CIC had the best pulmonary function (FEV₁=15±14.52%) and those with high levels of antibodies to this organism and high IgG-CIC levels had the poorest lung function (FEV₁=69.75±10.99%) (P<0.05). We believe that this indicates an immunologic basis for lung injury in cystic fibrosis.