In the process of renal fibrosis, macrophages not only act as immune cells, but also directly transform into myofibroblasts in the damaged kidney mediated by the TGFβ1/SMAD3 pathway, via a process known as macrophage-to-myofibroblast transition (MMT) (Tang et al., 2019). The gene discussed is TGFB1; the disease is renal fibrosis.