Increases in Activated T Lymphocytes, Eosinophils, and Cytokine mRNA Expression for Interleukin-5 and Granulocyte/Macrophage Colony-stimulating Factor in Bronchial Biopsies after Allergen Inhalation Challenge in Atopic Asthmatics

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Abstract
Immunohistology and in situ hybridization were used to evaluate the presence, activation status, and cytokine mRNA profile of cells in the bronchial mucosa during human allergen-induced asthma. Fifteen atopic asthmatic subjects underwent inhalation challenge with allergen and with allergen diluent, performed in random order separated by an interval of at least 3 wk. Bronchial biopsies were obtained 24 h after challenge. Immunostaining revealed increases in the numbers of secreting eosinophils (EG2+; P < 0.05) and in interleukin-2 receptor (IL-2R)-positive cells (CD25+; P < 0.01) after allergen compared with diluent challenge. No differences were observed in the numbers of total leukocytes (CD45+), T lymphocytes (CD3+, CD4+, and CD8+), elastase-positive neutrophils, macrophages (CD68+), or mast cell subtypes (MCT+ or MCTc+). In situ hybridization revealed significant increases in the numbers of cells expressing mRNA for IL-5 (P < 0.02) and granulocyte/macrophage colony-stimulating factor (P < 0.01) after allergen compared with diluent challenge. A significant inverse relationship was observed between the number of cells expressing mRNA for IL-4 and for interferon-γ (r = −0.75, P < 0.02). The results support the view that cytokines possibly from activated T lymphocytes may contribute to local eosinophil accumulation during allergen-induced asthma.