When comparing the other sIgG subclass levels between PSC and IAC patients, IgG1 and IgG3 levels were similar and mean sIgG2 levels were higher in IAC patients than in PSC patients (4.5 vs. 3.5; P < 0.001, t test; Table 1). Here, IGHG3 is linked to pancreatic serous cystadenoma.