Dose-response of proteinase inhibitors on CXCR1 and CXCR2 induced downmodulation. Purified peripheral blood PMNs were preincubated with various concentrations of (A) 1,10-phenanthroline (B) EDTA, or (C) bestatin for 30 minutes followed by the addition of LPS (100 ng/mL) (•), TNF- (50 ng/mL) (▪), or IL-8 (500 ng/mL) (▴) for 1 hour at 37°C. The x-axis indicates inhibitor concentration (μg/mL). The y-axis indicates percent inhibition of downmodulation.