Background: GATA-3 (GATA binding protein 3) and the proto-oncogene c-maf are Th2-regulating transcription factors that control the expression of interleukin (IL)-4 and IL-5, while T-bet (T-box expressed in T cells) is a Th1-specific transcription factor that controls the expression of interferon (IFN-gamma). Allergen provocation in asthmatics induces a Th2-dominated cytokine profile, but so far it is unknown whether the skewed cytokine expression is reflected by the expression of the respective transcriptional regulators.
Objective: The aim of this study was to determine the regulation of Th1- and Th2-specific transcription factors and cytokines in 10 atopic subjects with mild asthma and 5 nonatopic healthy controls at baseline and after segmental sham and allergen challenge.
Methods: The mRNA expression of GATA-3, c-maf and T-bet was determined by real-time polymerase chain reaction in bronchoalveolar lavage (BAL) cells and bronchial biopsies. The percentage of IL-4+, IL-5+ and IFN-gamma+ BAL T cells was determined by flow cytometry, and BAL levels of these cytokines were measured by ELISA.
Results: In BAL cells of asthmatics, the mRNA expression of all transcription factors was increased after allergen challenge. In bronchial biopsies, the basal expression of GATA-3 was increased in asthmatics compared to healthy controls but decreased after allergen challenge. Compared to sham challenge, the percentage of IL-5+/CD4+ BAL T cells was increased after allergen challenge in asthmatics while the percentage of IFN-gamma+/CD4+ and IFN-gamma+/CD8+ T cells was decreased. Expression of c-maf mRNA in BAL cells correlated with IL-4+/CD4+ BAL cells and BAL IL-5 levels.
Conclusions: Segmental allergen challenge in asthmatics leads to increased GATA-3, c-maf and T-bet expression in BAL cells but not in bronchial biopsies.
Copyright (c) 2006 S. Karger AG, Basel.