Erythrocyte-bound interleukin-8 and RANTES in human endotoxemia

Erythrocytes have been suggested to bind chemokines, thus limiting their effective concentration in the circulation. We investigated binding of the chemokines IL-8 and RANTES to erythrocytes following endotoxin challenge. Endotoxin caused a transient increase of IL-8 in plasma, and a gradual increase of erythrocyte-bound IL-8, remaining elevated for at least 24 h in vivo. Binding of IL-8 to erythrocytes was confirmed by incubation of freshly isolated erythrocytes with endotoxin stimulated plasma. Incubation for 1 h led to a decrease in plasma concentrations of IL-8 with a concomitant increase in erythrocyte-bound IL-8 levels. Erythrocyte-bound RANTES was induced early following endotoxin infusion and our data may suggest competition between the two chemokines for the-same binding site on erythrocytes in vivo. In conclusion, in humans, both IL-8 and RANTES are induced by endotoxin and are, at least in part, cleared from the plasma by binding to erythrocytes.