ObjectiveTo investigate the effects of forsythoside (FS) on immune regulatory mechanism of proliferation and secretion of NO and TNF-α of mouse spleen T and B lymphocytes in vitro. MethodsMouse spleen and splenocytes were prepared by aseptic separation and the cells were suspended with RPMI 1640 and cultured in RPMI 1640 containing 10% fetal bovine serum in vitro and stimulant concanavalin (ConA) and lipopolysaccharide (LPS). Different concentrations of 0,0 and 160 μg/mL FS were added separately in culture medium at different times. MTT was used to assay the changes of optical absorbance of T and B lymphocytes. ELISA and Griess methods were used to detect the TNF-α and NO levels. ResultsProliferation and survival rate of ConA-induced T lymphocytes treated with FS at low and medium concentration were significantly increased at 24 h and 48 h, and cell transformation was inhibited after FS induction for 72 h. LPS-induced splenic B cell proliferation and survival were significantly improved by FS at low concentration after 24 h. NO secretion of T and B lymphocytes was enhanced by FS at low and medium concentrations. TNF-α secretion of FS-treated B and T lymphocytes treated with FS at medium concentration was promoted, but TNF-α secretion of T lymphocytes was inhibited by FS at high concentration. In addition, FS had a significant effect on proliferation of splenic lymphocytes in vitro from mouse injected with cyclophosphamide, but no significant effect on the lymphocyte NO secretion. ConclusionOur findings suggest that FS may regulate immune cell function via lymphocyte proliferation and cytokine secretion.