ABCB4 and primary biliary cholangitis: Conversely, the expression is downregulated in end-stage human chronic liver injury [such as advanced primary biliary cirrhosis (PBC) and end-stage alcoholic liver disease (ALD)] and the animal model of primary sclerosing cholangitis, the Mdr2 gko mouse (Yao et al., 2011; Chowdhury et al., 2013).