Considering the tendency of higher ALP levels and higher prevalence of biliary tract involvement in the high IL-6 group, elevated serum IL-6 in IgG4-RD patients may originate from the hepatobiliary system, because IL-6 is significantly up-regulated by biliary epithelial cells, hepatocytes, and liver macrophages (Kupffer cells) in response to a variety of pathcomological conditions [30]-[31]. This evidence concerns the gene IL6 and immunoglobulin G4-related sclerosing disease.