Autoimmune Pancreatitis: An Autoimmune or Immunoinflammatory Disease?

Abstract

Autoimmune pancreatitis (AIP) has been widely presumed to be an autoimmune disease that is characterized by elevated IgG and/or IgG4, the presence of autoantibodies, and an infiltration of lymphocytes and plasma cells with fibrosis. However, no detailed immunological studies have been published. To define immunological changes in AIP in detail, and to review evidence for autoimmunity which may be antigen specific and may play a role in the pathogenesis of AIP, and therefore, to determine whether AIP is an autoimmune disease. A detailed immunological investigation for both innate and adaptive immune responses was performed in a patient with AIP. Review of literature was performed from Pub med, and Medline search. Immunological analysis of patient with AIP revealed increased production of proinflammatory IL-6, and IL-17, and increased NK cell activity. No organ-specific or non-specific antibodies were detected. There was no correlation between serum IgG4 with disease activity or response to steroid therapy. Review of literature revealed lack of auto-antigen-specific T and B cell responses in AIP, and autoantibodies are present only in a subset of patients, and are not specific to pancreatic tissue antigens. Therefore, we propose the term Immunoinflammatory pancreatitis rather than an autoimmune pancreatitis.