HLA-DRB1 and immunoglobulin G4-related sclerosing disease: (1) Type 1 AIP is an IgG4-related disease dominated by a Th2-type immune response, potentially associated with gene polymorphisms such as HLA-DRB1*0405 and FCGR2B;(2) Type 2 AIP is idiopathic duct-centric pancreatitis dominated by a Th1-type immune response, with fewer IgG4-positive cell infiltrations, and may be related to neutrophil extracellular traps (NETs) and cytokine storms (8).