Fig. 1.

Pathogenic mechanisms of IgG4-RD: a) Eventual initial mechanisms include local autoantigens, infectious agents, allergic components in a genetically predisposed individual; b) These factors activate immune reaction in the target tissue (organ/organs) which is characterized by Th2 predominance with an increased production of cytokines (IL-4, IL-5, IL-13) and tumour growth factor -b (TGF-b). Moreover, an activation of Treg, a release of IL-10 and elevated serum IgE occur. The immune reaction also causes a B cell class switching with an increased production of IgG4 producing plasma cells. APC = antigen presenting cell; Tc = cytotoxic T lymphocyte; Treg = regulatory T cell.