IL-17B is elevated in patients with pneumonia and mediates IL-8 production in bronchial epithelial cells

The role of IL-17B in regulating pulmonary immunity and inflammation is unknown. In this study, we found that IL-17B concentrations were significantly elevated in adult and paediatric patients with community-acquired pneumonia relative to their corresponding healthy adult and paediatric controls. The increased concentrations of IL-17B significantly and positively correlated with chemokine IL-8 concentrations in clinical pneumonia. In vitro studies demonstrated that IL-17B could induce gene and protein expression of IL-8 in human bronchial epithelial cells, but not lung fibroblasts, which was regulated by the activation of Akt, p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK) and nuclear factor-kappaB (NF-κB) signaling pathways. In vivo studies further showed that increased IL-17B levels significantly and positively correlated with IL-8 concentrations in experimental pneumonia. In conclusion, human pneumonia was associated with enhanced release of IL-17B, which might regulate pulmonary immunity and inflammation through the induction of IL-8 in bronchial epithelial cells.