CXCR2 expression and ligand binding of ST3Gal-IV^−/− leukocytes. (A) Surface expression of CXCR2 on GR-1–positive leukocytes of ST3Gal-IV^−/− and WT mice was analyzed by flow cytometry. Leukocytes were incubated with an allophycocyanin-labeled GR-1 mAb, a PE-labeled anti-CXCR2 mAb, and a PE-labeled isotype control. (B) For ligand binding studies, leukocytes from the peripheral blood of WT (n = 4), ST3Gal-IV^−/− (n = 3), and CXCR2^bm−/− (n = 3) mice were incubated with different dilutions of CF-CXCL8 and subsequently analyzed for bound fluorescence by flow cytometry. Peripheral blood leukocytes from WT mice were treated with 100 mU/ml neuraminidase for 60 min and investigated for CF-CXCL8 binding. Data are given as mean ± SD. P < 0.05 for WT versus ST3Gal-IV^−/−, CXCR2^bm−/−, and WT + Neu for 30 and 90 nM CF-CXCL8, respectively. MFI, mean fluorescence intensity.