Biliary atresia (BA) is a rare disease in infants, with unknown mechanisms of pathogenesis. It is characterized by hepatobiliary inflammatory, progressive destruction of the biliary system leading to liver fibrosis, and deterioration of liver function. Interleukin (IL) 17A promotes inflammatory and autoimmune processes. We studied the role of IL17A and cells that produce this cytokine in a mouse model of BA and in hepatic biopsy samples from infants with BA.