ARG1 and pulmonary fibrosis: Recent studies reveal that arginase1 (Arg1)+ pro-fibrotic macrophages are found in close proximity to pro-fibrotic fibroblasts within fibrotic regions, and that macrophage-specific deletion of Arg1 attenuates pulmonary fibrosis following fibrotic stimuli, suggesting that Arg1+ pro-fibrotic macrophages play an essential role in pulmonary fibrosis51.