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. 2023 Feb 9;13(2):333. doi: 10.3390/biom13020333

Figure 3.

Figure 3

CCL18 mediates the vicious loop of fibroblasts and alveolar macrophages to promote lung fibrosis. CCL18 is primarily produced by alveolar macrophages in IPF. Monomeric collagen type I induces Akt phosphorylation via CD204, shifting alveolar macrophages to the alternatively activated phenotype and augmenting CCL18 production. The enhanced CCL18 interacts with receptors in fibroblasts and induces collagen production via the ERK-Smad3-Sp1 transduction axis. As the effector cells in IPF, fibroblasts form a positive feedback loop with profibrotic alveolar macrophages via CCL18 and collagen. This vicious cycle plays a significant role in IPF.