Differential attenuation of β2 integrin-dependent and -independent neutrophil migration by Ly6G ligation

Abstract Antibody ligation of the murine neutrophil surface protein Ly6G disrupts neutrophil migration in some contexts but not others. We tested whether this variability reflected divergent dependence of neutrophil migration on β2 integrins, adhesion molecules that interact with Ly6G at the neutrophil surface. In integrin-dependent murine arthritis, Ly6G ligation attenuated joint inflammation, even though mice lacking Ly6G altogether developed arthritis normally. By contrast, Ly6G ligation had no impact on integrin- independent neutrophil migration into inflamed lung. In peritoneum, the role of β2 integrins varied with stimulus, proving dispensable for neutrophil entry in E. coli peritonitis but contributory in IL-1-mediated sterile peritonitis. Correspondingly, Ly6G ligation attenuated only IL-1 peritonitis, disrupting the molecular association between integrins and Ly6G and inducing cell-intrinsic blockade restricted to integrin-dependent migration. Consistent with this observation, Ly6G ligation impaired integrin-mediated postadhesion strengthening for neutrophils arresting on activated cremaster endothelium in vivo . Together, these findings identify selective inhibition of integrin- mediated neutrophil emigration through Ly6G ligation, highlighting the marked site and stimulus specificity of β2 integrin dependence in neutrophil migration. KEY POINTS The contribution of β2 integrins to neutrophil migration into inflamed tissues varies with site and stimulus. Ligation of Ly6G, a GPI-linked neutrophil surface protein, selectively attenuates β2 integrin-dependent neutrophil migration in vivo. Blockade correlates with disrupted interaction between Ly6G and β2 integrins and impaired integrin-mediated postadhesion strengthening.