CXCR4 and idiopathic pulmonary fibrosis: Numbers of circulating fibrocytes expressing the hematopoietic marker CD45 and the mesenchymal marker procollagen I as well as the chemokine receptor CXCR4 are increased in IPF (Mehrad et al. 2007; Andersson‐Sjoland et al. 2008) and PH (Yeager et al. 2012).