Defensins are antimicrobial and cytotoxic peptides that contain 29-35 amino acid residues, including six invariant cysteines whose intromolecular disulfide bonds cyclize and stabilize them in a complexly folded, triple stranded fj-sheet configuration. Generated by the proteolytic processing of 93-95 amino acid precursor peptides, they constitute> 5% of the total cellular protein in human and rabbit neutrophils (polymorphonucleated neutrophils-PMN) and are also produced by rabbit lung macro phages and by mouse and rabbit small intestinal Paneth cells. Despite their pro minence in rat PMN, defensins are not found in murine PMN. The anti microbial spectrum of defensins includes gram positive and gram negative bacteria, mycobacteria, T. pallidum, many fungi, and some enveloped