CXCR4 was the most up-regulated C-X-C chemokine receptor in both slow- and rapid-IPF relative to NDC lung fibroblasts, where this chemokine receptor was more abundantly expressed in rapid-IPF relative to slow-IPF and normal lung fibroblasts (Fig. 4J). The gene discussed is CXCR4; the disease is idiopathic pulmonary fibrosis.