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 in the number of peripheral blood eosinophils at 24 hours. In situ hybridization of peripheral 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 or protein. In contrast, both bronchoalveolar lavage eosinophils and mononuclear cells expressed GM-CSF mRNA and protein.

CONCLUSION

These studies suggest that the expression of GM-CSF by eosinophils after allergen inhalation is compartmentalized to the lungs.