Defective cellular immunity to gram-negative bacteria in cystic fibrosis patients.

In vitro lymphocyte responses to Pseudomonas aeruginosa have been found to be 
impaired in cystic fibrosis patients with advanced clinical disease. The responses 
to Klebsiella pneumoniae, Serratia marcescens, and Proteus mirabilis were studied in 
a similar group of cystic fibrosis patients and normal individuals. Cystic 
fibrosis patients found to be unresponsive to pseudomonas were also unresponsive 
to klebsiella, serratia, and proteus. Responsiveness to Staphylococcus aureus was not 
impaired in cystic fibrosis patients. We postulate that in vitro lymphocyte 
responses to several gram- negative bacteria require the function of a 
lymphocyte subpopulation which may be impaired in some cystic fibrosis patients. 
