title: Heparin binding protein (CAP37) is an opsonin for Staphylococcus aureus and increases phagocytosis in monocytes.
abstract: Heparin binding protein (HBP), also known as cationic antibiotic protein (CAP37) or azurocidin, is stored in azurophilic granules of neutrophils and is released to the extracellular space when granulocytes phagocytose Staphylococcus aureus. We investigated whether extracellular HBP also has the potential to increase phagocytosis of S. aureus by other phagocytes. We used flow cytometry to characterize the binding of HBP to S. aureus and to simultaneously measure phagocytosis and superoxide production of opsonized S. aureus in monocytes and granulocytes. Our results demonstrate that HBP is a strong opsonin for S. aureus, and that monocytes, but not granulocytes, increase phagocytosis of HBP-treated S. aureus. However, HBP-treated S. aureus increases the production of superoxide in both monocytes and granulocytes as compared with untreated S. aureus. These findings support the role of granulocytes in the afferent limb of inflammation and demonstrate that HBP, when released from activated granulocytes, potentiates bacterial uptake in monocytes and enhances the potential of microbial killing in monocytes and granulocytes.
authors.affiliation: Department of Physiology and Biophysics, University of Louisville School of Medicine, Kentucky, USA.
authors.forename: M
authors.initials: M
authors.lastname: Heinzelmann
authors.forename: A
authors.initials: A
authors.lastname: Platz
authors.forename: H
authors.initials: H
authors.lastname: Flodgaard
authors.forename: F N
authors.initials: FN
authors.lastname: Miller
mesh_terms: D023181:Antimicrobial Cationic Peptides; D001798:Blood Proteins / Q000276:immunology* / Q000378:metabolism; D002352:Carrier Proteins / Q000276:immunology* / Q000378:metabolism; D006098:Granulocytes / Q000276:immunology / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007249:Inflammation / Q000209:etiology; D009000:Monocytes / Q000276:immunology* / Q000378:metabolism; D009895:Opsonin Proteins / Q000276:immunology* / Q000378:metabolism; D010587:Phagocytosis / Q000276:immunology*; D011485:Protein Binding; D011994:Recombinant Proteins / Q000276:immunology / Q000378:metabolism; D013211:Staphylococcus aureus / Q000276:immunology*; D013481:Superoxides / Q000378:metabolism
chemical_list: C062991:AZU1 protein, human; D023181:Antimicrobial Cationic Peptides; D001798:Blood Proteins; D002352:Carrier Proteins; D009895:Opsonin Proteins; D011994:Recombinant Proteins; D013481:Superoxides