IgG4-Related Disease and Innate Immunity.

An increased number of clinicopathological studies on autoimmune pancreatitis, cholangitis, and sialoadenitis have led to the recognition of immunoglobulin G4-related disease (IgG4-RD) as a novel disorder, characterized by elevated levels of serum IgG4 and infiltration of IgG4-expressing plasma cells in the affected organs. Although the immunological background associated with the development of IgG4-RD remains poorly understood, recent studies have suggested involvement of the innate immune response in its pathogenesis. Peripheral blood innate immune cells, such as plasmacytoid dendritic cells and monocytes isolated from patients with IgG4-RD, promote IgG4 production by B cells. Activation of the innate immune response by microbe- and/or damage-associated molecular patterns stimulates production of type I interferon and B cell-activating factor by innate immune cells and results in IgG4 production by B cells. Elucidation of the innate immune response associated with IgG4-RD may help identify a new therapeutic target for this immune disorder.