Objective To investigate the effect of interleukin-6 (IL-6) on the apoptosis of annulus fibrosus (AF) cell induced by interleukin-1β (IL-1β). Methods Cultured AF cells were divided into 6 groups and treated with no drug, 10 ng/mL IL-6,10 ng/mL IL-1β,10 ng/mL IL-1β and Z-VAD-FMK (a caspase-9 inhibitor),10 ng/mL IL-1β and 10 ng/mL IL-6,10 ng/mL IL-1β and 100 ng/mL IL-6, respectively. After three days of culture, the apoptosis rate, the positive rates of caspase-3, -8, and -9 of AF cells were detected with flow cytometry. Results The apoptosis rates of cells in group 1 to 6 were 2.67%±1.08%, 2.71%±0.53%, 20.37%±1.57%, 11.34%±0.67%, 18.17%±0.74%, and 9.42%±1.08%, respectively. There was no significant difference between group 1 and 2, while the apoptosis rates of group 4, 5, and 6 were significantly lower than group 3 (P=0.001,P=0.172, and P=0.001, respectively). Positive rates of caspase-3 in group 5 (12.35%±0.64%) and 6 (9.26%±0.36%) were significantly lower than group 3 (17.14%±0.72%; P=0.001 and P<0.001, respectively). And positive rates of caspase-9 in group 5 (15.13%±1.45%) and 6 (10.17%±2.50%) were significantly lower than group 3 (19.4%±0.98%; P=0.014 and P=0.004, respectively). But there was not obvious change of caspase-8 activity after IL-6 was added. Conclusion IL-6 is capable of protecting AF cells from IL-1β induced apoptosis in vitro. Mechanism of the protection is related with the inhibition of caspase-3 and -9 activities. Objective To investigate the effect of interleukin-6 (IL-6) on the apoptosis of annulus fibrosus (AF) cell induced by interleukin-1β. Methods Cultured AF cells were divided into 6 groups and treated with no drug, 10 ng / mL IL-1, 10 ng / mL IL-1β and Z-VAD-FMK (a caspase-9 inhibitor), 10 ng / mL IL-1β and 10 ng / mL IL -6,10 ng / mL IL-1β and 100 ng / mL IL-6, respectively. After three days of culture, the apoptosis rate, the positive rates of caspase-3, -8, and -9 of AF cells were detected with flow cytometry. Results The apoptosis rates of cells in group 1 to 6 were 2.67% ± 1.08%, 2.71% ± 0.53%, 20.37% ± 1.57%, 11.34% ± 0.67%, 18.17% ± 0.74%, and 9.42% ± There was no significant difference between group 1 and 2, while the apoptosis rates of groups 4, 5, and 6 were significantly lower than group 3 (P = 0.001, P = 0.172, and P = 0.001, respectively) . Positive rates of caspase-3 in group 5 (12.35% ± 0.64%) and 6 (9.26% ± 0.36%) were significantly lower than group 3 (1 7.14% ± 0.72%; P = 0.001 and P <0.001, respectively). And positive rates of caspase-9 in group 5 (15.13% ± 1.45%) and 6 19.4% ± 0.98%; P = 0.014 and P = 0.004, respectively). It was not obvious that IL-6 was capable of protecting AF cells from IL-1β induced Mechanism in the protection is related with the inhibition of caspase-3 and -9 activities.