Using a murine model of lung fibrosis, Phillips et al. (2004) have identified several populations of fibrocytes based on their surface expression of the chemokine receptors CXCR4 and CCR7 in mice, CD45+ COLI+ CXCR4+ CCR7-, and CD45+ COLI+ CXCR4- CCR7+. This evidence concerns the gene CXCR4 and pulmonary fibrosis.