A total of 46.2% (30/65) of PSC patients were positive for either one of the two target-specific PAbs (anti-CUZD1 and anti-GP2), with a significant difference compared to healthy controls (0.0%, P < 0.001) and all disease control groups (CD: 26.8%, P < 0.001 and UC: 7.6%, P < 0.001 or aLC: 6.7%, chrHCV: 4.2% and PBC: 4.9%, P < 0.001 for all CLD). Here, GP2 is linked to congenital secretory chloride diarrhea 1.