In brief, reduced mRNA levels of amongst others Col1a1 have been reported in the liver of a mouse model of non-alcoholic fatty liver disease (NAFLD) upon injection with M2c macrophages expressing MERTK [61], which has been suggested to induce TGFβ secretion in the context of Immunoglobulin G4 (IgG4)-related disease [64]. Here, COL1A1 is linked to metabolic dysfunction-associated steatotic liver disease.