Cytokine profiles of BAL T cells and T-cell clones obtained from human asthmatic airways after local allergen challenge

Background: This study assessed the heterogeneity of cytokine expression in asthma before and after local allergen challenge. Methods: BAL T cells were obtained 10 min or 24 h after local endobronchial allergen challenge in atopic asthmatic subjects. T cells were cloned by direct limiting dilution, mRNA expression was assessed by RT-PCR, and cytokine protein production by ELISA. Results: Unstimulated baseline BAL T cells expressed mRNA for IFN-γ, IL-13, and TNF-α. A minority of samples expressed IL-4 and IL-5, but no IL-3 mRNA was detected. PHA stimulation increased expression of IL-3, IL-4, and IL-5 mRNA in 4/6 samples. IL-13 and GM-CSF mRNA were found in BAL cells after allergen challenge, but expression of IFN-γ was reduced. Both IL-4 and IL-3 were strongly upregulated after PHA stimulation, while the expression of TNF- α and IFN-γ was reduced, compared to equivalent baseline samples. Seventeen panels of BAL T-cell clones were derived (average cloning efficiency 1/40 T cells). Seven panels survived to 8 weeks for analysis. Clones derived 4 h after saline challenge showed strong mRNA signals for IL-13, IL-4, and IFN- γ, whereas clones derived 24 h after allergen challenge expressed IL-13, GM- CSF, IL-3, IL-4, and often IL-5 (i.e., closer to the Th2 profile). There was considerable heterogeneity in the patterns of cytokine mRNA and protein production by different clones. Conclusions: T cells from asthmatic airways produce IL-13, IFN-γ, and TNF-α, but after allergen challenge, type 2 cytokines are upregulated, mRNA and protein analysis provide complementary information on airways T-cell cytokine profiles.