Differences in Lectin‐Like Oxidized Low‐Density Lipoprotein Receptor‐1 Expression and Chemotaxis Between Neutrophils in the Oral Cavity and Those in Whole Blood

AIMS: The abundance of neutrophils (polymorphonuclear cells, PMNs) in the oral cavity both in health and disease suggests that PMNs play a significant role in maintaining oral immune equilibrium. This cross-sectional, in vitro study characterizes the surface epitopes, oxidative burst, and migratory properties of oral (oPMNs) and circulating (cPMNs) neutrophils in healthy volunteers. METHODS: cPMNs were isolated from whole blood samples using gravity sediment separation; oPMNs were obtained from filtrated saliva. Surface epitopes and oxidative burst were analyzed with flow cytometry. PMN surface morphology was visualized with scanning electron microscopy (SEM) with gold labeling. A µ-slide chemotaxis assay was conducted. RESULTS: oPMNs showed significantly higher LOX-1 expression than cPMNs (~1000 times). In contrast to oPMNs, cPMNs could be stimulated with PMA or TNF-α, resulting in a significant LOX-1 increase. PMA induced a stronger increase of LOX-1 than TNF-α. Only stimulation with TNF-α or PMA resulted in the upregulation of CD11b and CD66b and the downregulation of CD62L on cPMNs. SEM showed an abundance of CD66b and diverging surface morphologies between oPMNs and cPMNs. Unlike cPMNs, oPMNs did not show chemotactic migration along an fMLP-gradient. CONCLUSION: Our study highlights the high expression of LOX-1 on oPMNs associated with a lack of further stimulability and absent in vitro chemotactic migration, indicating that these cells are in a higher state of activation than cPMNs. These findings provide new insights into the phenotypic and functional characteristics of oral neutrophils.