SFTPD and idiopathic pulmonary fibrosis: Thus, in a recent Greek cohort study, elevated serum levels of Krebs von Den Lungen-6 (KL-6), SP-D, VEGF-A, IGFBP-1, ICAM-1, and C-C motif ligand-18 (CCL18) were measured in sera samples of IPF individuals using ELISA.