The importance of CXCL12 has also been shown in patients with interstitial lung disease [28]; in this study, not only were the numbers of CD45 + collagen I + CXCR4 + fibrocytes significantly higher than in normal controls, but expression of CXCL12 was markedly elevated in the lung and plasma of patients with lung fibrosis [28]. This evidence concerns the gene PTPRC and interstitial lung disease.