Bratke K, et al. – The expression and regulation of PD–1 and its ligands in human allergic asthma were investigated. This study was the first to demonstrate that a low PD–1 expression by circulating CD4+ T cells was linked to high total and specific (against the allergen used for provocation) IgE concentrations in allergic asthma. A differential regulation of PD–1 ligands on endobronchial DCs after allergen challenge was indicated, which seemed to favour Th2–inflammation.