Primary biliary cholangitis (PBC) is an autoimmune liver disease with a strong hereditary component. Here, we report a genome-wide association study that included 1,122 PBC cases and 4,036 controls of Han Chinese descent, with subsequent replication in a separate cohort of 907 PBC cases and 2,127 controls. Our results show genome-wide association of 14 PBC risk loci including previously identified 6p21 (HLA-DRA and DPB1), 17q12 (ORMDL3), 3q13.33 (CD80), 2q32.3 (STAT1/STAT4), 3q25.33 (IL12A), 4q24 (NF-κB) and 22q13.1 (RPL3/SYNGR1). We also identified variants in IL21, IL21R, CD28/CTLA4/ICOS, CD58, ARID3A and IL16 as novel PBC risk loci. These new findings and histochemical studies showing enhanced expression of IL21 and IL21R in PBC livers (particularly in the hepatic portal tracks) support a disease mechanism in which the deregulation of the IL21 signalling pathway, in addition to CD4 T-cell activation and T-cell co-stimulation are critical components in the development of PBC.

Multiple genome-wide association studies of primary biliary cirrhosis (PBC) in both European and Japanese ancestries have shown significant associations of many genetic loci contributing to the susceptibility to PBC. Major differences in susceptibility loci between these two population groups were observed. In this study, we examined whether the most significant loci observed in either European and/or Japanese cohorts are associated with PBC in a Han Chinese population. In 1070 PBC patients and 1198 controls, we observed highly significant associations at CD80 (rs2293370, P=2.67×l0−8) and TNFSF15 (rs4979462, P=3.86×10−8) and significant associations at 17q12-21 (rs9303277), PDGFB (rs715505), NF-κB1 (rs7665090), IL12RB2 (rs11209050), and STAT4 (rs7574865; all corrected P values <0.01). However, no association was observed for POU2AF1 (rs4938534), IL12A (rs485499 and rs2366408), IL7R (rs6897932), CXCR5 (rs715412), SOCS1 (rs725613), and TNFRSF1A (rsl800693). STAT4 (rs7574865) was strongly associated after additional control samples were analyzed. Our study is the first large-scale genetic analysis in a Han Chinese PBC cohort. These results do not only reflect that Han Chinese PBC patients share common genetic susceptibility genes with both their Japanese and European counterparts but also suggest a distinctly different genetic susceptibility profile.

Anti‐nuclear antibodies to speckled 100 kDa (sp100) and glycoprotein 210 (gp210) are specific serologic markers of primary biliary cholangitis (PBC) of uncertain/controversial clinical or prognostic significance. To study the genetic determinants associated with sp100 and gp210 autoantibody subphenotypes, we performed a genome‐wide association analysis of 930 PBC cases based on their autoantibody status, followed by a replication study in 1,252 PBC cases. We confirmed single‐nucleotide polymorphisms rs492899 (P = 3.27 × 10−22; odds ratio [OR], 2.90; 95% confidence interval [CI], 2.34‐3.66) and rs1794280 (P = 5.78 × 10−28; OR, 3.89; 95% CI, 3.05‐4.96) in the human major histocompatibility complex (MHC) region associated with the sp100 autoantibody. However, no genetic variant was identified as being associated with the gp210 autoantibody. To further define specific classical human leukocyte antigen (HLA) alleles or amino acids associated with the sp100 autoantibody, we imputed 922 PBC cases (211 anti‐sp100‐positive versus 711 negative cases) using a Han Chinese MHC reference database. Conditional analysis identified that HLA‐DRβ1‐Asn77/Arg74, DRβ1‐Ser37, and DPβ1‐Lys65 were major determinants for sp100 production. For the classical HLA alleles, the strongest association was with DRB1*03:01 (P = 1.51 × 10−9; OR, 2.97; 95% CI, 2.06‐4.29). Regression analysis with classical HLA alleles identified DRB1*03:01, DRB1*15:01, DRB1*01, and DPB1*03:01 alleles can explain most of the HLA association with sp100 autoantibody. Conclusion: This study indicated significant genetic predisposition to the sp100 autoantibody, but not the gp210 autoantibody, subphenotype in PBC patients. Additional studies will be necessary to determine if these findings have clinical significance to PBC pathogenesis and/or therapeutics.

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