Red blood cells are a sink for interleukin 8, a leukocyte chemotaxin.

IL-8 (also known as neutrophil-activating peptide 1) is recognized as a potent effector of neutrophil functions. Several different cell types that contact blood, namely T lymphocytes, monocytes, and endothelial cells, secrete this polypeptide following stimulation by cytokines, or lipopolysaccharide. Here we show that when IL-8 is added to blood it rapidly partitions from the plasma fluid to the blood cells and that erythrocytes account for the vast majority of this binding. Analysis of '"IIL-8 binding (lala-IL-8177 form) to human red cells indicates a single, 5 nM Kd affinity class of binding sites, present at 2,000 per red cell representing - 15 nmol of red cell IL-8 binding sites per liter of blood. These sites are protease sensitive. Their binding of IL-8 is rapidly reversible and does not result in receptor internalization, although bound IL-8 is resistant to extraction bypH 3 buffer at 5°C. 125IIL.8 binding to red cells was not inhibited by epidermal growth factor or interleukin 1, but was inhibited by monocyte chemotactic peptide-1, which is not a neutrophil chemotaxin, but is a member of the same family of polypeptides as IL-8. FACSO analysis of IL-8mediated mobilization of Ca21 in neutrophils indicates that the IL-8 bound to red cells is incapable of stimulating neutrophils. Thus, red cell absorption of IL-8 may function to limit stimulation of leukocytes by IL-8 released into blood. (J. Clin. Invest. 1991. 88:1362-1369.) Key words: neutrophil-activating peptide 1 * monocyte chemotactic peptide 1 * erythrocyte * neutrophil * fluorescence activated cell sorter analysis - equilibrium