Lymphocyte responsiveness to Pseudomonas aeruginosa in cystic fibrosis: Relationship to status of pulmonary disease in sibling pairs.

Lymphocyte proliferative responses to Pseudomonas aeruginosa and Staphylococcus aureus were evaluated in six sibling pairs with cystic fibrosis. In each pair, one sibling had advanced clinical disease, whereas the other sibling was in good clinical condition. Three in this latter group had no clinically apparent Pseudomonas bronchitis. In all cases, the average responses to Pseudomonas isolated from each sibling pair were lower in the sibling with advanced clinical disease. This difference was not observed in the responses to Staphylococcus. Normal plasma or plasma from patients with CF in good clinical condition does not restore the responses in patients with advanced clinical disease. However, plasma from patients with low or no responses to Pseudomonas inhibits the responses of responding siblings. A progressive specific lymphocyte unresponsiveness to Pseudomonas may play an important role in the increasing destructiveness of chronic pulmonary Pseudomonas infection in cystic fibrosis.