Receptor binding studies involving AT III and IL-8 receptors.

Human neutrophils were incubated with ¹²⁵I–IL-8 (2000 Ci/mM) at a concentration of 10 μM plus or minus an excess of unlabeled IL-8 (○) or AT III (●) in PBS–0.5% BSA for 90 minutes at 4°C. After incubation, cells were washed twice with PBS–0.5% BSA, added to 0.5 mol/L saline, and centrifuged at 200g for 10 minutes. Activities were counted in a Beckman gamma counter. IL-8 receptor internalization (deactivation) was measured by the preincubation of cells with IL-8, fMLP, or AT-III for 5 minutes according to previous time-course experiments. Results are expressed as mean cpm, compared by Mann-Whitney test after Kruskal-Wallis analysis of variance (P < .001). **P < .01. ns, not significant; n = 6.