Pathogenic role of immune response to M3 muscarinic acetylcholine receptor in Sjögren’s syndrome-like sialoadenitis

The aim of this study was to clarify the role of the immune response to muscarinic type 3 receptor (M3R) in the pathogenesis of Sjögren’s syndrome (SS). M3R−/− mice were immunized with murine M3R peptides and their splenocytes were inoculated into Rag1−/− (M3R−/−→Rag1−/−) mice. M3R−/−→Rag1−/− mice had high serum levels of anti-M3R antibodies and low saliva volume. Histological examination showed marked infiltration of mononuclear cells in the salivary glands and immunohistochemistry demonstrated that the majority of these cells were CD4+ T cells with a few B cells and several IFN-γ- and IL-17-producing cells. Apoptotic cells were present in the salivary glands of M3R−/−→Rag1−/− mice. Moreover, transfer of only CD3+ T cells from M3R−/− immunized with M3R peptides into Rag1−/− mice resulted in cell infiltration and destruction of epithelial cells in the salivary glands, suggesting that M3R reactive CD3+ T cells play a pathogenic role in the development of autoimmune sialoadenitis. Our findings support the notion that the immune response to M3R plays a crucial role in the pathogenesis of SS-like autoimmune sialoadenitis.