Interleukin-12 exacerbates Sjögren's syndrome through induction of myeloid-derived suppressor cells

Interleukin (IL)-12 modulates the generation and function of various immune cells and plays a vital role in the pathogenesis of Sjögren's syndrome (SS). Myeloid-derived suppressor cells (MDSCs) are involved in autoimmune diseases by regulating various immune responses. However, it has not been confirmed whether inflammatory IL-12 participates in the progression of SS via regulating MSDCs. In the present study, the plasma levels of IL-12 were detected by ELISA in SS-like non-obese diabetic (NOD) mice. The mice were treated by intraperitoneal injection of IL-12 and anti-IL-12 antibody, respectively, and then the salivary flow rate was detected. The pathology of submandibular glands was evaluated in tissue sections stained with hematoxylin and eosin. The proportion of MDSCs was assessed by flow cytometry. The results showed that plasma IL-12 was significantly increased in the SS-like NOD mice comparing with that noted in the control mice. The exogenous IL-12 exacerbated SS-like symptoms of NOD mice and promoted the generation of both bone marrow (BM) and splenic MDSCs in the SS-like NOD mice. Of note, anti-IL-12 alleviated SS-like symptoms of NOD mice and inhibited the generation of BM and splenic MDSCs. Moreover, the generation of MDSCs was crippled in the IL-12-deficient C57BL/6 (Il-12(−/−) B6) mice. Our findings suggest that aggravation of SS-like symptoms by IL-12 in NOD mice may be attributed to its promotion of MDSC development.