目的　探讨IFN γ对沙眼衣原体 (Chlamydiatrachomatis,Ct)感染细胞的细胞毒作用的特点及可能机制。方法　用MTT法检测IFN γ对感染Ct (K血清型 )的McCoy细胞的细胞毒作用 ,酶法检测NO的含量 ,应用NO合酶抑制剂N 硝基左旋精氨酸 (L NNA)分析细胞毒作用与NO水平的关系。结果　①IFN γ对Ct感染的McCoy细胞产生显著的细胞毒作用 ,且呈时间和剂量依赖性 ;随着Ct感染剂量的加大 ,IFN γ的细胞毒作用增强 ;L NNA剂量依赖性地阻断IFN γ对Ct感染细胞的细胞毒作用。②IFN γ诱导Ct感染的McCoy细胞分泌NO ,且IFN γ作用浓度增大和作用时间延长 ,NO含量增大 ;L NNA剂量依赖性地抑制了IFN γ所诱生的NO的合成。结论　①IFN γ对Ct感染的McCoy细胞产生细胞毒作用 ,且呈时间和剂量依赖性 ;细胞毒作用随Ct感染量增加而增大 ;②NO可能是IFN γ对Ct感染细胞产生细胞毒作用的效应分子。 Objective To investigate the cytotoxicity of IFN γ against Chlamydia trachomatis (Ct) infected cells and its possible mechanism. Methods The cytotoxicity of IFNγ against McCoy cells infected with Ct (serotype K) was detected by MTT assay. The content of NO was detected by enzyme-linked immunosorbent assay (ELISA) and the cytotoxicity of N-nitro-L-arginine Role and the relationship between the level of NO. Results ① IFNγ had a significant cytotoxic effect on Ct-infected McCoy cells in a time-and dose-dependent manner. The cytotoxicity of IFNγ was enhanced with the increase of Ct infection dose. LNA treatment dose-dependently blocked IFN Cytotoxic effect of γ on Ct infected cells. ② IFN-γ-induced McCoy cells secreted NO, and the concentration of IFNγ was increased and the action time was prolonged. The content of NO was increased. L-NNA inhibited the production of NO induced by IFNγ in a dose-dependent manner. CONCLUSION: ① IFNγ exerts a cytotoxic effect on Ct-infected McCoy cells in a time and dose-dependent manner. Cytotoxicity increases with the increase of Ct infection. ②NO may be an effector molecule of IFNγ on Ct-infected cells .