Basophils activated via TLR signaling may contribute to pathophysiology of type 1 autoimmune pancreatitis

BACKGROUND: Pathophysiology of type 1 autoimmune pancreatitis (AIP) is still unclear. We previously reported that M2 macrophages might play an important role in type 1 AIP. Recently, it has been reported that basophils regulate differentiation to M2 macrophages. In this study, we investigated basophils from the pancreatic tissue and peripheral blood of individuals with type 1 AIP. METHODS: By using immunohistochemistry, we investigated basophils in pancreatic tissue from 13 patients with type 1 AIP and examined expression of toll-like receptors (TLRs) by these cells. Additionally, we obtained peripheral blood samples from 27 healthy subjects, 40 patients with type 1 AIP, 8 patients with alcoholic chronic pancreatitis, 10 patients with bronchial asthma, and 10 patients with atopic dermatitis, and analyzed activation of basophils by stimulating them with ligands of TLR1–9. We also compared TLR expression in basophils from the tissue and blood samples. RESULTS: Basophils were detected in pancreatic tissues from 10 of 13 patients with type 1 AIP. Flow cytometric analysis revealed that the ratios of basophils activated by TLR4 stimulation in type 1 AIP (9.875 ± 1.148%) and atopic dermatitis (11.768 ± 1.899%) were significantly higher than those in healthy subjects (5.051 ± 0.730%; P < 0.05). Levels of basophils activated by TLR2 stimulation were higher in seven type 1 AIP cases. Furthermore, stimulation of TLR2 and/or TLR4, which were expressed by basophils in pancreas, activated basophils in peripheral blood. CONCLUSIONS: Basophils activated via TLR signaling may play an important role in the pathophysiology of type 1 AIP.