Abstract: Objective · To investigate the immunoregulatory effect of dihydromyricetin (DMY) on the spleens of rats with rheumatoid arthritis. Methods · Thirty Wistar rats were randomly divided into five groups, i.e., normal group, model group and DMY administration groups (5, 25, and 50 mg/kg). The type Ⅱ collagen-induced rheumatoid arthritis (CIA) model was established in model group and DMY administration groups. DMY administration groups were intraperitoneally injected with DMY every other day at set doses. After five weeks of administration, rats of each group were sacrificed, and the spleens were taken out to prepare tissue sections, and pathological changes were observed after hematoxylin-eosin staining. The spleen lymphocytes of model group were isolated, and the effect of DMY on the proliferation of spleen lymphocytes in inflammatory state was detectedcell-counting-kit 8. The percentages of different subsets of T lymphocytes were detectedflow cytometry. The of inflammatory factors in spleen lymphocytes was determinedPCR and ELISA. Results · Compared with model group, inflammation-related pathological changes in the spleens of DMY-administered groups were significantly relieved. DMY could inhibit the proliferation of spleen lymphocytes, reduce the percentage of CD3+CD4+ cells and slightly increase the percentage of CD3+CD8+ cells after the treatment of concanavalin (ConA) in vitro. The results of PCR and ELISA showed that DMY could inhibit the of proinflammatory cytokines and promote the of anti-inflammatory factors both in vitro and in vivo. Conclusion · DMY has immunomodulatory effects on immune-associated T lymphocytes in the spleens of CIA rats in vivo and in vitro, thereby inhibiting systemic inflammatory response.

Key words: rheumatoid arthritis, dihydromyricetin, spleen, T lymphocyte, rat