Specifically, imbalance of the Th17/Treg ratio among CD4<sup>+</sup> T cells, clonal expansion of bile duct-specific CD8<sup>+</sup> T cells, and quantitative and functional abnormalities of unconventional T cell subsets - including γδ T cells, double-negative T cells, mucosal-associated invariant T cells, and invariant natural killer T cells - are closely associated with disease activity, cholangitis severity, and fibrosis progression. This evidence concerns the gene CD4 and cholangitis.