Flow cytometry analysis of IL-8 binding to RBCs. RBCs (5 × 10⁴) from the Fy(a−b^weak) donors SEV and BAR and from Fy(a−b+) and Fy(a−b−) controls with the determined genotypes FY*B/*B and FY*Fy/*Fy, respectively, were incubated with increasing concentration of fluorescent FITC-conjugated IL-8. Chemokine binding was analyzed by flow cytometry. Results are expressed as the specific IL-8 binding (arbitrary units) versus ligand concentration. Nonspecific signal was determined when incubation with the FITC-labeled IL-8 was performed in presence of a 100-fold excess of unlabeled IL-8.