Notably, substantially reduced numbers of hepatic DUOX2+ACE2+ small cholangiocytes were observed in PBC patients with positive AMA-M2 (PBC-M2+) or negative AMA-M2 (PBC-M2−), but not in patients with obstructive cholestasis (OC), secondary sclerosing cholangitis (SSC), and nonalcoholic steatohepatitis (NASH) (Fig. 3g and Supplementary Table 9). Here, DUOX2 is linked to primary biliary cholangitis.