Effect of the aminopeptidase inhibitor bestatin on LPS-, TNF-–, and IL-8–induced downmodulation of CXCR1 and CXCR2. Purified peripheral blood PMNs were preincubated with bestatin (100 μmol/L) for 30 minutes in media (RPMI/10% fetal calf serum) 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. (A) CXCR1 and (B) CXCR2 expression was measured cytofluorometrically.