ACE2 and primary biliary cholangitis: Interestingly, it was also noted that: a) the number of DUOX2+ ACE2+ cholangiocytes decreased with the development and progression of PBC; b) the polymeric immunoglobulin receptor (pIgR) was highly expressed in DUOX2+ ACE2+ cholangiocytes; c) the expression of serum anti-pIgR autoantibodies was highly increased in both positive and negative AMA-M2 of PBC patients (217).