CXCL13 and idiopathic pulmonary fibrosis: Numerous blood-derived biomarkers have been identified in IPF, including MMP-7, MUC-1 (KL-6), ICAM-1, IL-8, VCAM-1, SP-A, SP-D, CXCL13, CCL18, COMP, and markers of extracellular matrix turnover, among others (27, 56).