TLR4 and immunoglobulin G4-related sclerosing disease: It was reported that Toll-like receptors (TLRs) and natural killer cells play an important role in PBC patients.[26] Stimulation with TLR3 and TLR4 ligands can enhance IgG4 production by peripheral blood mononuclear cells in IgG4-RD patients.[27] Therefore, abnormal innate immune responses against microbial antigens may contribute to the pathogenesis of both IgG4-RD and PBC.