Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease frequently associated with intestinal inflammation, mainly ulcerative colitis. The etiopathogenesis has not been elucidated but compromises in the gut-liver crosstalk are suggested in which macrophages are implemented. The immunological profile and importance of monocyte-/macrophage-populations will be investigated, including the role of macrophage-Trem2, a recently identified marker in experimental PSC/colitis.