ABSTRACT
<p><b>OBJECTIVE</b>To investigate the effect of kirenol on bovine type II collagen (CII)-specific lymphocytes in vivo and in vitro, and explore the mechanism of kirenol-induced immunosuppression in antigen-specific lymphocytes.</p><p><b>METHODS</b>Twenty-four Wistar rats were randomized into control group, collagen-induced arthritis (CIA) model group, kirenol group (2 mg/kg), and prednisolone group (2 mg/kg). After CII injection, the rats in the latter two groups received intragastric administration of kirenol and prednisolone for 30 days, and the spleens and draining lymph nodes of the rats were harvested to prepare single cell suspensions for measurement of the cytokine levels using ELISA. In the in vitro experiment, the lymphocytes from the control rats, with or without 20 µg/ml CII treatment in the presence of 0-80 µg/ml kirenol, were evaluated for cell proliferation and apoptosis using [(3)H]-thymidine incorporation and flow cytometry, respectively.</p><p><b>RESULTS</b>Compared with those in CIA group, IFN-γ and TNF-α production was significantly reduced in splenocyte culture supernatant of kirenol group (P<0.05 and P<0.01, respectively), and the level of IL-10 and IL-4 was up-regulated (P<0.05 and P<0.01, respectively); IFN-γ and TNF-α secretion by the cultured lymph node cells (LNCs) significantly decreased (P<0.05 and P<0.001, respectively) and IL-10 and IL-4 production increased (P<0.05, P<0.001) in kirenol group. In the in vitro experiment, kirenol treatment caused obvious suppression of CII-induced LNC proliferation and dose-dependently induced antigen-specific apoptosis of the splenocytes and LNCs.</p><p><b>CONCLUSION</b>Kirenol treatment reduces pro-inflammatory cytokine secretion, increases anti-inflammatory cytokine production, inhibits cell proliferation and induces apoptosis of CII-specific lymphocytes in vitro, suggesting the potential of kirenol as an immunosuppressant.</p>