CCL2 and idiopathic pulmonary fibrosis: In patients with idiopathic pulmonary fibrosis (IPF), the TLR9s, which normally appear in the immune cells of healthy individuals, were detected in pulmonary epithelial and smooth muscle cells.[7] These activated TLR9s may express cytokine C C motif ligand 2 (CCL2) to promote lung fibrosis, deteriorating the process.