Objective To investigate the effect of IL-21 on secretion of IFN-γ in CD8⁺ T cells of rhesus monkeys infected by SHIV. MethodsThe in vitro study was carried out on the culture of CD8⁺ T cells isolated from rhesus monkey models infected by SHIV. CD8⁺ T cells were incubated with various concentrations of IL-21 (1～15 ng/mL). Then IFN-γ concentrations in the supernatant were detected by ELISA, RT-PCR was performed to detect the expression of IFN-γ mRNA in the CD8⁺ T cells, and the percentage of IFN-γ-positive CD8⁺ T cells was assayed by flow cytometry. ResultsIL-21 (10 ng/mL) significantly increased IFN-γ level (P <0.05) in the supernatant of CD8⁺ T cell culture, compared with that in the control group. The expression of IFN-γ mRNA was significantly enhanced. IFN-γ which requires de novo synthesis following activation peaked at 4 h post stimulation. ConclusionIL-21 can increase the secretion of IFN-γ in vitro. 