Interactions of Neisseria gonorrhoeae with human neutrophils: Effects of serum and gonococcal opacity on phagocyte killing and chemiluminescence

Abstract

Our data suggest that serum does not affect the ability of piliated transparent or nonpiliated opague gonococci to stimulate chemiluminescence (CL), except at very low ratios of gonococci to neutrophils. The biological relevance of the minimal CL observed at these low ratios can be debated. Stimulation by serum of CL induced by type 1, 2, or 3 gonococci occurred only when neutrophils were producing 0.3% of the maximal experimental CL measured. The interactions of gonococci with CGD neutrophils were unexpected. Since gonococci are strongly catalase positive, it would be hypothesized that they would not be killed within CGD neutrophils, since there would be no available H2O2. On the contrary, gonococci were killed as well by CGD neutrophils as they were by normal neutrophils. The explanation for this is presently unknown; however, the results strongly suggest that nonoxidative mechanisms play an important role in the intraleukocytic killing of N. gonorrhoeae. It has been shown previously that type 1 and 4 gonococci are readily killed in vitro by human neutrophil granule contents, by apparently nonoxidative mechanisms. It has also been shown that Pseudomonas aeruginosa, another gram-negative, catalase-positive organism, is killed equally well by normal neutrophils, CGD neutrophils, and normal neutrophils under anaerobic conditions.