Redistribution of selectin counter-ligands induced by cytokines

Soluble recombinant (r) P-selectin and rP-selectin immobilized on plastic s urfaces were tested for their capacity to activate neutrophils to produce s uperoxide anion. Soluble rP-selectin was incapable of activating leukocytes , whereas immobilized rP-selectin was able to induce leukocyte activation. When neutrophils were pretreated with a low dose of IL-8, granulocyte colon y stimulating factor or granulocyte macrophage colony stimulating factor, s oluble rP-selectin was no longer inert. These cytokine-primed leukocytes pr oduced superoxide anion in the presence of soluble rP-selectin, During this priming period, sialyl Lewis X (sLe(x)) epitopes redistributed to one end of the leukocytes. Similar polarization of sLe(x) epitopes was observed at the attachment site of cells that adhered to immobilized rP-selectin. Cap f ormation and superoxide anion production induced by solid-phase P-selectin or by IL-8 and soluble rP-selectin treatment were inhibited by treatment of the leukocytes with cytochalasin B. These observations suggest that the re distribution of the carbohydrate ligands and the polarization of the leukoc yte surface through an active process is a prerequisite but not sufficient to leukocyte superoxide production through P-selectin.