Our results suggested the profibrotic cytokines TGFB1, IL1B and IFNG induce fibrosis and that Tregs might produce some of these cytokines in IgG4-related thymitis as well as in the other affected lesions of IgG4-related disease. This evidence concerns the gene TGFB1 and immunoglobulin G4-related sclerosing disease.