BACKGROUND: Autoimmune pancreatitis (AIP) is a distinct type of pancreatitis associated with a presumed autoimmune mechanism. The aim of this study was to analyze the clinical features and expressions of forkhead box P3 (Foxp3) and interleukin-17 (IL-17) in type 1 AIP in China and to identify factors for differentiation of AIP from non-AIP chronic pancreatitis (CP).

MATERIAL AND METHODS: We retrospectively reviewed pancreatic specimens with diagnosis of type 1 AIP and non-AIP CP at Sun Yat-Sen Memorial Hospital in China from January 2000 to December 2013. The clinical symptoms, serological data, imaging findings, histopathology, and immunohistochemical findings of Foxp3 and IL-17 in the 2 groups were analyzed.

RESULTS: Twenty-nine patients with type 1 AIP and 20 patients with non-AIP CP were enrolled. Obstructive jaundice was more common in type 1 AIP than in non-AIP CP (62.1% vs. 30.0%, P=0.042). The diffuse or segmental enlargement of the pancreas was more frequent in type 1 AIP than in non-AIP CP (72.4% vs. 40.0%, P=0.038). Histopathology of type 1 AIP presented dense lymphoplasmacytic infiltration, “snowstorm-like” fibrosis and abundant immunoglobulin (Ig) G4+ cells. Foxp3+ cells were more frequently observed in type 1 AIP than in non-AIP CP. IL-17+ cell infiltration was similar between the 2 groups. Furthermore, a positive correlation was found between Foxp3+ and IgG4+ cell counts in the pancreas of patients with type 1 AIP.

CONCLUSIONS: Type 1 AIP has distinctive symptoms, image, and pathological characteristics, which could be used for differentiation from non-AIP CP. Foxp3+ cells might be helpful to distinguish type 1 AIP from non-AIP CP.

Keywords: Cholangiopancreatography, Magnetic Resonance, Autoimmune Diseases - radiography, Forkhead Transcription Factors - metabolism, Immunoglobulin G - metabolism, Interleukin-17 - metabolism, Pancreatitis - radiography, Pancreatitis, Chronic - radiography, Tomography, X-Ray Computed