There exist several indirect hints that microbes are involved in the pathogenesis of PBC and PSC: a polyclonal IgM response in PBC [47,48,49], which can be frequently observed during chronic infections; an increased risk of patients with recurrent urinary tract infections to develop PBC [50,51,52,53,54,55]; and the close association of PSC with inflammatory bowel disease (IBD), particularly ulcerative colitis (UC) [56,57]. Here, CD40LG is linked to primary biliary cholangitis.