Recent studies suggested the existence of two subtypes of Autoimmune pancreatitis (AIP) , type 1in IgG4-related dis­ ease (IgG4-RD) , and type 2 related with a granulocytic epithelial lesion. Apart from type 2 AIP, T helper type 2 (Th2) immune response seems to be dominated over Thl in type l/IgG4-RD. Recent human and experimental animal studies have suggested that base on genetic back ground involvement of innate immunity in addition to acquired immunity, such as bacterial/viral infections, and IgG4 production of monocytes/basophils with TLR/NOD stimulation. Based on update findings, we have proposed a hypothesis for the development of type 1 AIP. The basic concept is the biphasic mechanism of “induction” and “progression”. An initial abnormal innate immune response to unknown disease-related antigens including self-antigens (LF, CA II, CA-IV, PSTI, amylase, annexinA11, laminin 511, or galectin3, etc), PAMPs, DAMPs or microorganisms (virus or bacteria) might be induced by decreased naive Tregs from the thymus and CD19+ CD24highCD27+ Bregs from the bone marrow, which is followed by a Th1 immune response with the release of pro-inflammatory cytokines (IFN-g, IL-1 beta, IL-2, TNFα). Subsequently, a Th2 type immune response with IgG, IgG4 and autoantibodies is induced by IL-4 or IL5 from activated basophils and M2 macrophage. Production of IgG4 may be reciprocally regulated by IL-10 from increased ICOS+ inducible i-Tregs and CD19+CD24highCDD38high Bregs and by BAFF from basophils, pDC and other innate immune cells. Session #1 Recording Link: