Quantitative studies on immunologically specific and non-specific absorption of Pseudomonas aeruginosa antibodies in serum from cystic fibrosis patients

A quantitative determination of anti-Pseudomonas immunoglobulins was carried out by means of rocket-line immunoelectrophoresis in the serum from 19 cystic fibrosis (CF) patients with chronic P. aeruginosa infection and with many precipitins against these bacteria (CF + P). from six CF patients without P. aeruginosa infection (CF-P) and from nine normal persons. On an average P. aeruginosa antigens could absorb 7.7% of IgG, 8.4% of IgA and 29% of IgM from CF + P sera, whereas no detectable IgG and IgA and only 14.6% IgM were absorbed from normal sera and only 1.2% of IgG, 3.8% of IgA, but 29% of IgM was absorbed from CF-P sera. The results show that most, if not all, of the P. aeruginosa precipitins belong to the IgG and IgA classes, but that these precipitins can account only for part of the increased levels of immunoglobulins in CF-P patients. Staphylococcus aureus containing protein A (strain Cowan 1) could absorb 95% of the precipitating antibodies against P. aeruginosa and 92% of IgG, 27% of IgA and 34% of IgM in CF-P patients. The absorption of P. aeruginosa precipitins by protein A points to a possible synergism between S. aureus and P. aeruginosa infections in the lungs of CF patients, since S. aureus may interfere with antibody-mediated immune elimination of P. aeruginosa. Such a mechanism may also facilitate infections with other microorganisms in these patients.