Recent advances in autoimmune pancreatitis.

Area of Science:

• Gastroenterology
• Immunology
• Pathology

Background:

• Autoimmune pancreatitis (AIP) is a distinct form of chronic pancreatitis.
• It presents as two subtypes: Type 1 (lymphoplasmacytic sclerosing pancreatitis) and Type 2 (duct-centric pancreatitis).
• Type 1 AIP is a systemic disease associated with immunoglobulin G4 (IgG4)-positive plasma cells, while Type 2 lacks systemic involvement.

Purpose of the Study:

• To differentiate Autoimmune pancreatitis (AIP) from other chronic pancreatitis forms.
• To describe the distinct clinical and histological features of Type 1 and Type 2 AIP.
• To highlight the autoimmune etiology suggested by steroid responsiveness and lymphoplasmacytic infiltrates in AIP.

Main Methods:

• Clinical and histological examination of AIP cases.
• Characterization of cellular infiltrates, including immunoglobulin G4 (IgG4)-positive plasma cells.
• Review of existing literature and development of animal models for AIP.

Main Results:

• Type 1 AIP shows systemic involvement and abundant IgG4-positive plasma cells.
• Type 2 AIP is characterized by duct-centric lesions without systemic disease.
• Serum IgG4 levels are consistently elevated in Type 1 AIP, but its pathogenic role is unclear.

Conclusions:

• Autoimmune pancreatitis (AIP) is classified into two distinct subtypes with differing characteristics.
• The autoimmune basis of AIP is suggested by its response to steroids, yet autoantigens and effector cells are not fully identified.
• Further research, including animal models, is crucial for understanding AIP pathogenesis, particularly the role of IgG4 in Type 1 AIP.