Peptide Ac2-26 inhibits fMLP-induced changes in CD11b expression or on polymorphonuclear leukocytes (PMN) prepared from WT or FPR KO mice.

Blood aliquots were incubated with peptide Ac2-26 (200 μg/mL or 66 μM) or Boc2 (100 μM) for 10 minutes prior to addition of fMLP. CD11b expression on the cell surface was measured by flow cytometry 15 minutes later. (A) Basal CD11b levels on blood PMN in WT (▪) and FPR KO (■) mice. (B) Concentration-response curves for fMLP in neutrophils taken from WT (●) and FPR KO (○) mice. Data are mean ± SEM of n = 6 to 8 experiments performed with n = 3 to 4 mice each. *P < .05 versus unstimulated cells (basal values were 86 ± 9 and 54 ± 3 units of fluorescence intensity for WT and FPR KO cells, respectively). (C) Peptide Ac2-26 blocks both 3 and 30 μM fMLP-induced CD11b up-regulation on WT PMN. Data are mean ± SEM of n = 4 to 6 experiments performed with n = 3 mice each. *P < .05 versus unstimulated cells (basal values were 82 ± 4 units of fluorescence intensity). (D) Effect of peptide Ac2-26 and Boc2 on 30 μM fMLP-induced CD11b up-regulation in neutrophils from FPR KO mice. Data are mean ± SEM of n = 3 to 5 experiments performed with n = 3 mice each. *P < .05 versus unstimulated cells (basal values in absence of fMLP were 56 ± 4 units of fluorescence intensity).