PTPRC and pulmonary fibrosis: Since CD45+/COL1+/CXCR4+ fibrocytes were expanded in the bone marrow and have been reported to contribute to bleomycin-induced pulmonary fibrosis [24], we next stained the PBMC-differentiated cells with antibodies specific for CD45, Collagen I, and CXCR4 (Figure 4(b)).