ABCB4 and biliary atresia: Similarly, as confirmed in this study, early in the course of biliary atresia in infants, most canalicular transporters are downregulated, including bile salt export pump (BSEP, ABCB11), multidrug-resistant protein 3 (MDR3, ABCB4), and the multidrug-resistant associated protein 2 (MRP2, ABCC2) (5).