Abstract: Objective: To explore the effect of Mycobacterium tuberculosis antigen(Mtb-Ag) on spontaneous apoptosis of neutrophils.Methods: The fresh isolated neutrophils from healthy adult blood were cultured with Mtb-Ag for 24 h,with or without pretreatment of Mek inhibitor PD98059 for 30 min.Wright-Giemsa stainnin,Annexin-V staining and flow cytometry were used to measure cell apoptosis of neutrophils.Results: Compared to the spontaneous apoptosis(55±10)% of neutrophils cultared in vitro for 24 h,the cell apoptosis of neutrophils cultured with Mtb-Ag(1.125 mg/ml) decreased(31±3)%(P<0.01);pretreatment of PD98059 inhibited the anti-apoptosis effects of Mtb-Ag on neutrophils(P<0.01).Conclusions: Mtb-Ag prevents neutrophils from spontaneous apoptosis and its inhibitory role involves extracellular signal-regulated kinase pathway.