FAP and pulmonary fibrosis: Activated fibroblast is a key cell in pulmonary fibrosis pathogenesis, and fibroblast activation protein (FAP), a 97 kDa type II transmembrane protein, with dipeptidyl peptidase activity as one kind of serine protease, only overexpressed on the membrane of aberrantly activated fibroblast, had been proved that could be found at the remolding area of IPF and cancer (Garin-Chesa et al., 1990; Acharya et al., 2006; Keane et al., 2013).