Enhanced expression of platelet-activating factor receptor on human eosinophils by interleukin-3, interleukin-5 and granulocyte-macrophage colony-stimulating factor

The effects of interleukin-3 (IL/3), IL-5 and granulocyte-macrophage colony-stimulating factor (GM-CSF) on the surface expression of platelet-activating factor (PAF) receptor on eosinophils was examined using a PAF receptor binding assay. Specific binding of [H-3]WEB 2086, a specific ligand for PAF receptor, to peripheral blood eosinophils obtained from healthy individuals was significantly increased when the cells were cultured with IL-3, IL-5, or GM-CSF for 12 h, compared with untreated cells. The PAF-induced increase in intracellular calcium ion concentration in eosinophils was markedly augmented by exposure to IL-5 for 12 h. These results suggest that these cytokines modulate the responsiveness of eosinophils to PAF through enhancement of PAF receptor expression on the cell surface.