Demonstration of neutrophil chemotactic activity in the sputum of cystic fibrosis patients with Pseudomonas aeruginosa infection

The pathogenesis of tissue damage in the lungs of cystic fibrosis patients with chronic P. aeruginosa infection is quite complex and not well understood. Inflammatory cells, particularly neutrophils, are accumulated in the damaged tissues and in the sputum. This study demonstrates the presence of a heat-stable neutrophil chemotactic factor(s) in the sputum of CF patients. The chemotactic activity seems to be associated with the endotoxin present in the sputum. Chemotaxis of sol phase sputum was determined in a modified Boyden chamber assay. It was found that the sputum obtained from the patients showed strong chemotactic activity for peripheral blood neutrophils of normal individuals. The activity was greater than twice that of casein, a strong neutrophil chemo-attractant. Sputum at about dilution of 1:50 exhibited chemotactic activity equal to that of casein. Heat treatment of the sputum at 56 degrees C for 30 min, to inactivate complement, and at 100 degrees C for 15 min, to denature other proteins, somewhat reduced the chemotactic activity, but there was still strong chemotactic activity. The presence of endotoxin was demonstrated in both the non-heated and the heated samples by LAL and rocket immunoelectrophoresis. It is concluded that the sputum of CF patients contain chemotactic activity of heat-stable nature and most likely of bacterial origin endotoxin. These factors are involved in attraction of neutrophils to the lungs and sputum of these patients and contribute to the tissue damage of cystic fibrosis.