Specific binding of human interleukin-3 and granulocyte-macrophage colony-stimulating factor to human basophils

The human T cell-derived cytokines interleukin (IL)-3 and granulocyte-macrophage colony-stimulating factor (GM-CSF) were examined for their ability to bind to human basophils. Basophils were obtained from the peripheral blood of a patient with chronic myeloid leukemia undergoing basophilic differentiation after purification on a density gradient of metrizamide. Binding studies with 125I-labeled IL-3 and 125I-labeled GM-CSF demonstrated that basophils express a single class of high-affinity receptors for each of these molecules. Saturation binding curves with 125I-labeled IL-3 revealed that IL-3 bound specifically to basophils, and analysis according to the method of Scatchard revealed that basophils express 800 to 900 receptors per cell with an apparent dissociation constant of 2.6 × 10 −11 mol/L. Saturation-binding curves with 125I-labeled GM-CSF revealed that basophils express 100 to 200 receptors per cell with an apparent dissociation constant of 4 × 10 −11 mol/L. The demonstration of high-affinity receptors for IL-3 and GM-CSF on human basophils suggests a role for these cytokines in the regulation of basophil function.