[Activity of defensins from human neutrophils against Mycobacterium avium complex]

We examined the activity of defensins from human neutrophils against Mycobacterium avium complex (MAC). MAC were cultured in the presence of defensins at 37 degrees C for 4-48 hours. After incubation, colony counts were enumerated by colony-forming units (CFU). Human neutrophil peptide-1 (HNP-1) at 5 micrograms/ml had the ability to kill MAC. We tested 8 strains of MAC. HNP-1 was successful in killing every strain, although the degree of killing varied from strain to strain. We also found that HNP-2 and HNP-3 were as effective in killing MAC as HNP-1. We suggest that defensins play an important role in the host defenses against MAC.