CXCL10 and chronic obstructive pulmonary disease: Since increased activity of the IFN-γ/IL-12 pathway as well as increased levels of IP-10 in COPD is most likely due to a complex interaction between lung epithelial cells and white blood cells, we decided to investigate the role of the IFN-γ/IL-12 pathway on IP-10 secretion upon the interaction of peripheral blood mononuclear cells with two human lung epithelial cell lines, A549 (alveolar epithelial cell line), Calu-3 (bronchial epithelial cell line) in addition to primary normal human bronchial epithelial (NHBE) cells.