Interestingly, in a transgenic murine model of PBC (dominant-negative form of transforming growth factor beta receptor type II) deletion of the p40 subunit, but not the p35 subunit resulted in amelioration of disease severity (32, 33), suggesting an important role for IL-23, but not IL-12 in this pathology. The gene discussed is IL23A; the disease is primary biliary cholangitis.