Th17 cells have been shown to play an important role in the pathogenesis of a variety of
autoimmune diseases. The aim of this study was to investigate the potential role of Th17 cells in
autoimmune pancreatitis (AIP). Quantitative real-time polymerase chain reaction (qRT-PCR) was performed to determine gene expression of the signature
cytokines of Th17 cells
IL-17A and
IL-21 and of the Th17 lineage-specific
transcription factor retinoic acid receptor-related orphan receptor C (RORC) in human tissue specimens of AIP, classical
chronic pancreatitis (CP), and normal pancreas (NP). Infiltrating immune cells were characterized by immunohistochemistry (IHC). Gene expression of
IL-17A,
IL-21, and RORC were found to be significantly increased in AIP. Accordingly, the number of Th17 cells was significantly increased in AIP compared to NP or CP. Both gene expression analysis and IHC revealed a clear difference between type 1 and 2 AIP. In the periductal compartment of
type 2 AIP, which is characterized by granulocytic epithelial lesions (
GELs), the number of infiltrating Th17 cells and neutrophilic granulocytes was significantly increased compared to
type 1 AIP. Our data suggest that Th17 cells play a role in the pathogenesis of AIP, in particular of
type 2 AIP. Cross-talk between Th17 cells and neutrophilic granulocytes mediated via
IL-17A may be a potential mechanism by which neutrophils are recruited to the duct and acinar cells with subsequent destruction, a process that is pathognomonic for
type 2 AIP.