Priming of polymorphonuclear neutrophilic leukocyte oxidative activity by type 1 pili from Escherichia coli

Preincubation of human polymorphonuclear leukocytes with free whole type 1 pili derived from Escherichia coli or with subunits of type 1 pili significantly augmented subsequent stimulation of cellular oxygen uptake by formyl-methionyl-leucyl-phenylalanine, concanavalin A, opsonized zymosan, or latex particles coated with whole type 1 pili. No such priming of leukocyte activation occurred if phorbol myristate acetate was used as a stimulant or if bovine serum albumin was substituted for the type 1 pili preparations. When free in solution, neither pili preparation directly stimulated cellular oxidative metabolism. Type 1 pili-mediated priming was not inhibited by polymyxin B, by mannose congeners, or by boiling the pili preparations but was prevented by trypsinization of the pili. This priming property indicates a further means by which type 1 pili may modulate the inflammatory response of the host and provides another tool that can be used to dissect the relationship between the structure and function of type 1 pili and to characterize leukocyte receptors for these pili.