[Characterization of a receptor for interleukin-5 on pulmonary eosinophils with eosinophilic pneumonia]

Interleukin-5 (IL-5) acts on eosinophil differentiation and activation, suggesting the existence of a membrane receptor for IL-5 on eosinophils. Here, we report that 125I-labeled recombinant human IL-5 bound to high affinity receptors on human eosinophils, especially pulmonary eosinophils in eosinophilic pneumonia obtained bronchoalveolar lavage (BAL). No specific binding occurred on neutrophils, nor on the undifferentiated eosinophilic cell line. EoL-3, in the absence of stimulation. The specific binding of IL-5 was induced by incubation at 37 degrees C of human eosinophils and EoL-3 cells with GM-CSF and with the supernatants of BAL cells from patients with eosinophilic pneumonia. These results indicate the existence of a specific binding site for IL-5 on human eosinophils with variable affinity in eosinophil hypodense or normodense subpopulations, as previously reported for other membrane receptors. Furthermore, lung cells (BAL cells) in patients with eosinophilic pneumonia may be involved in the production certain eosinophilopoietic growth cytokines such as IL-3, GM-CSF and IL-5.