Triple positive CXCR4+/CD45+/CXCL12+ cells (‡) were only evident to any extent in IPF lung tissue (Fig. 3k) and there were also CXCR4+ cells which did not express CD45 or CXCL12 (Fig. 3l) that did not appear to be of epithelial morphology. The gene discussed is PTPRC; the disease is idiopathic pulmonary fibrosis.