Gut Microbiota Involved in the Immunopathogenesis of Autoimmune Pancreatitis

Autoimmune pancreatitis (AIP), which is considered the pancreatic expression of a systemic immunoglobulin G4-related disease, is characterized by excessive infiltration of plasmacytes bearing immunoglobulin G4 and a unique form of fibrosis in multiple organs. This relatively new disease entity has garnered great attention from clinicians, but its pathophysiology remains poorly understood. Recent discoveries indicate that plasmacytoid dendritic cell activation followed by robust production of type I interferon and interleukin-33 plays a key role in driving chronic fibro-inflammatory responses in both murine and human AIP. Furthermore, the compositional alterations in the gut microbiota, known as intestinal dysbiosis, triggered plasmacytoid dendritic cell-driven pathogenic type I interferon responses. Intestinal dysbiosis is associated with a breakdown in intestinal barrier function; thus, we examined whether the latter condition affects the development of experimental AIP. Our recent research has revealed that intestinal barrier disruption worsens experimental AIP by facilitating the translocation of pathogenic bacteria, such as Staphylococcus sciuri, to the pancreas from the gut. These results indicate the "gut-pancreas axis" underlies the immunopathogenesis of AIP, and the maintenance of intestinal barrier integrity can prevent the worsening of AIP by inhibiting pancreatic colonization by harmful gut bacteria. In this mini review, the interactions between AIP development and gut microbiota are discussed with the aim of providing useful information not only for researchers but also for clinicians.