Effect of CKLiK^297-321 peptide on respiratory burst and phagocytosis. (A) Granulocytes were isolated and treated with GM-CSF (10^-10 M) to prime the cells. Cells were then treated without (-) or with increasing concentrations of CKLiK^297-321 or a scrambled tat-control peptide for 20 minutes. Respiratory burst was initiated with fMLP (10^-6 M). ROS production was measured by cytochrome c reduction, resulting in a change of optical density (OD) at a wavelength of 550 nm. An average of 3 independent experiments is depicted. (B) Granulocytes and FITC-labeled AfC (ratio 1:2) together with no, 1%, or 10% NHS were incubated for 15 minutes at 37°C to allow phagocytosis in the presence or absence of 50 mM CKLiK^297-321 or tat-control peptide. The percentage of AfC-phagocytosed neutrophils was detected by FACS analysis. Mean percentage of FITC-positive neutrophils ± SEM of 3 independent experiments is depicted. Student t test demonstrated a significant inhibition with P < .05.