CXCL12: CXCL12 (SDF-1), a CXCR4 ligand linked to lymphopoiesis and hematopoietic progenitor cell circulation/homing [10,16], may drive tissue fibrosis in IPF by binding to CXCR4. This evidence concerns the gene CXCR4 and idiopathic pulmonary fibrosis.