MPO-mediated PMN-motility is dependent on electrostatic interactions. (A) Methanol (MeOH) treatment of PMN did not impair MPO-induced motility, while directed movement of MeOH-fixed PMN toward MPO was blunted in buffer with the pH raised to the isoelectric point of MPO (pI 9.2, white bar, n = 3–4, one-way ANOVA P < .0001). (B) Poly-L-arginine (PLA), protamine and histone H2A were coadministered to PMN-suspension and MPO to equalize the cationic gradient. HSA was coadministered as a control protein (n = 3, one-way ANOVA P < .0001). (C) MPO-directed locomotion of sepharose beads with anionic or cationic coating was tested (n = 3-6). (D) Coadministration of PLA, protamine, and histone H2A impaired the motility of anionic beads toward MPO. In this case, n denotes number of independent experiments, number of donors of PMN ≥ 3. Bars represent means; error bars, SEM. *P < .05, **P < .01, ***P < .001.