Compartmentalization of eosinophil granulocyte-macrophage colony-stimulating factor expression in patients with asthma

Background: In patients with asthma the endobronchial instillation of an allergen induces recruitment of granulocyte-macrophage colony-stimulating factor (GM-CSF) messenger RNA-positive eosinophils into the airway. Objective: The goal of the study was to determine whether peripheral blood (as opposed to bronchoalveolar lavage) eosinophils express GM-CSF mRNA and protein. Methods: We performed in situ hybridization and immunocytochemistry on peripheral blood eosinophils, obtained at 0, 4, and 24 hours after either inhalation of diluent, inhalation of allergen, or endobronchial instillation of allergen. Results: Each study subject (n = 6) had both an immediate and late-phase response to allergen inhalation but not to diluent inhalation. Allergen, but not diluent, challenge induced a significant increase ease in the number. of peripheral blood eosinophils at 24 hours. In situ hybridization of peripheral,nl blood eosinophils with a sulfur 35-labeled GM-CSF RNA riboprobe and immunostaining with a GM-CSF monoclonal antibody revealed that neither pre- nor postchallenge (allergen or diluent) peripheral blood eosinophils expressed GM-CSF mRNA of protein. In contrast, both bronchoalveolar lavage eosinophils and mononuclear cells expressed GM-CSF mRNA and protein. Conclusion: These studies suggest that die expression of GM-CSF by eosinophils after allergen inhalation is compartmentalized ro die lungs.