CCL7 and pulmonary fibrosis: In contrast, in mice in which the CCL12 gene in alveolar epithelial cells has been conditionally knocked out, the expression of CCL2 and CCL7 in lung tissue and bronchoalveolar lavage fluid was not different from that in normal control mice, confirming that the conditional knockout of the CCL12 gene in alveolar epithelial cells can protect mice from developing pulmonary fibrosis [56].