CD177 participates in a novel mechanism for regulating neutrophil recruitment (P3093)

Abstract

Abstract Background: Neutrophils are the sine qua non of inflammatory arthritis, and contribute to pain, swelling, and tissue injury, rendering neutrophil migration to the joint a potential therapeutic target. We recently found that the murine neutrophil surface protein Ly6G modulates chemotaxis via interaction with β2 integrins. Whereas CD177 is a neutrophil-specific human protein in the same gene family, we sought to identify the role of CD177 in human neutrophil recruitment. Method: Flow cytometry was used to analyze the levels of cell surface proteins in circulating neutrophils and in neutrophils from inflamed joints. Fluorescence lifetime imaging microscopy/Fluorescence resonance energy transfer assay (FLIM/FRET) was used to quantify CD177-β2 integrin interactions. Result: In patients with rheumatoid arthritis, synovial neutrophils exhibit higher levels of surface CD177 expression comparing with blood neutrophils. Using FLIM/FRET, ~40% CD11a and ~20% CD11b β2 integrins interact with CD177 on surface of resting blood neutrophils. In vitro, a specific CD177 antibody inhibits LTB4-induced conformational activation of CD11b β2 integrin, which is correlated with an impaired neutrophil migration towards LTB4 in anti-CD177 treated cells in a transwell system. Conclusion: CD177 regulates neutrophil chemotaxis and may serve as a potential neutrophil-specific therapeutic target in neutrophilic inflammatory diseases such as arthritis.