title: The bacterial peptide N-formyl-Met-Leu-Phe inhibits killing of Staphylococcus epidermidis by human neutrophils in fibrin gels.
abstract: To study human neutrophil (polymorphonuclear leukocyte (PMN)) migration and killing of bacteria in an environment similar to that found in inflamed tissues in vivo, we have used fibrin gels. Fibrin gels (1500 microm thick) containing Staphylococcus epidermidis were formed in Boyden-type chemotaxis chambers. PMN migrated < 300 microm into these gels in 6 h and did not kill S. epidermidis when the gels contained heat-inactivated serum, C5-deficient serum, a streptococcal peptidase specific for a fragment of cleaved C5 (C5a), or anti-C5aR IgG. In contrast, in gels containing normal human serum, PMN migrated approximately 1000 microm into the gels in 4 h and into the full thickness of the gels in 6 h, and killed 90% of S. epidermidis in 6 h. fMLP reduced PMN migration into fibrin gels and allowed S. epidermidis to increase by approximately 300% in 4 h, whereas leukotriene B(4) stimulated PMN to migrate the full thickness of the gels and to kill 80% of S. epidermidis in 4 h. We conclude that both complement opsonization and C5a-stimulated chemotaxis are required for PMN bacterial killing in fibrin gels, and that fMLP inhibits PMN bactericidal activity in fibrin gels. The latter finding is surprising and suggests that in the presence of fibrin fMLP promotes bacterial virulence.
authors.affiliation: Department of Physiology and Cellular Biophysics, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA.
authors.forename: Yongmei
authors.initials: Y
authors.lastname: Li
authors.forename: John D
authors.initials: JD
authors.lastname: Loike
authors.forename: Julia A
authors.initials: JA
authors.lastname: Ember
authors.forename: P Patrick
authors.initials: PP
authors.lastname: Cleary
authors.forename: Emily
authors.initials: E
authors.lastname: Lu
authors.forename: Sadna
authors.initials: S
authors.lastname: Budhu
authors.forename: Long
authors.initials: L
authors.lastname: Cao
authors.forename: Samuel C
authors.initials: SC
authors.lastname: Silverstein
mesh_terms: D018829:Adhesins, Bacterial; D000328:Adult; D001426:Bacterial Proteins / Q000494:pharmacology*; D002464:Cell Migration Inhibition; D002634:Chemotaxis, Leukocyte / Q000187:drug effects / Q000502:physiology; D003176:Complement C3 / Q000378:metabolism; D015936:Complement C5a / Q000378:metabolism / Q000494:pharmacology; D003165:Complement System Proteins / Q000502:physiology; D010450:Endopeptidases / Q000494:pharmacology; D005337:Fibrin; D005782:Gels; D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism; D007975:Leukotriene B4 / Q000494:pharmacology; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D009504:Neutrophils / Q000187:drug effects* / Q000201:enzymology / Q000382:microbiology / Q000502:physiology*; D009895:Opsonin Proteins / Q000378:metabolism; D010587:Phagocytosis / Q000187:drug effects*; D013212:Staphylococcus epidermidis / Q000187:drug effects* / Q000254:growth & development* / Q000302:isolation & purification; D013297:Streptococcus pyogenes
chemical_list: D018829:Adhesins, Bacterial; D001426:Bacterial Proteins; D003176:Complement C3; D005782:Gels; D007074:Immunoglobulin G; D009895:Opsonin Proteins; D007975:Leukotriene B4; D009240:N-Formylmethionine Leucyl-Phenylalanine; C023976:N-formylmethionyl-methionyl-phenylalanine; D015936:Complement C5a; D005337:Fibrin; D003165:Complement System Proteins; D010450:Endopeptidases; C053088:C5a peptidase