Cellular immunity to bacteria: impairment of in vitro lymphocyte responses to Pseudomonas aeruginosa in cystic fibrosis patients.

Lymphocyte responses to the mitogens phytohemagglutinin and concanavalin A and to Streptococcus pyogenes, Staphylococcus aureus, Haemophilus influenzae, and Pseudomonas aeruginosa were evaluated in patients with cystic fibrosis and in normal individuals. Lymphocyte proliferation in vitro was stimulated by gentamicin-killed whole bacteria, and the proliferative response was measured by [3H]thymidine incorporation. The in vitro lymphocyte responses to antibiotic-killed bacterial reached maximum thymidine incorporation after 5 days in culture and followed a unimodal dose-response curve for each of the bacteria studied. A significant specific incapacity to respond to P. aeruginosa was detected in cystic fibrosis patients with advanced clinical disease.