Reduced hepatitis and CYP2E1 autoantibodies in IL-4-deficient mice, as well as the detection of CYP2E1 IgG4 subclass autoantibodies in patients with anesthetic hepatitis, support a role for IL-4 in the development of CYP2E1 autoantibodies and hepatitis (4, 9, 12). This evidence concerns the gene CYP2E1 and hepatitis A virus infection.