CF neutrophil killing of P. aeruginosa is impaired and further compromised in a chloride-poor environment. The rate of PsA killing, indicated by the first-order rate constant (% per minute), by normal (solid bars) or CF (open bars) PMNs in chloride-poor medium (0 mM chloride) or chloride-rich medium (127 mM chloride). Error bars represent standard error of the mean (n = 5 donors each). **P ≤ .05, for comparisons of the indicated means by Student t test. Reprinted from reference 89.