Most patients with PSC also have inflammatory bowel disease (IBD), which makes PSC a model disease for studying the gut–liver axis, suggesting that intestinal microorganisms may contribute to the occurrence of PSC.68In a study conducted by Tedesco et al,69a comparison was made between a multidrug resistance gene 2 knockout (Mdr2 −/− ) mouse model and an FVB/NJ mouse model. Here, ABCB4 is linked to inflammatory bowel disease.