Abstract: Objective To explore the role of Toll like receptor 2(TLR2) and its related cytokines in Legionella infection by in vitro experiment.Methods Peripheral blood mononuclear cells(PBMCs) were obtained from healthy subjects(n=30) and were stimulated with live Legionella pneumophila(Lp) for 18,24,and 72 hours.The mRNA expression levels of TLR2 and myeloid differentiation factor 88(MyD88) in PBMCs were determined using real-time reverse transeription PCR(RT-PCR).The expression levels of tumor necrosis factor-α(TNF-α),interleukin-1β(IL-1β),and interleukin-6(IL-6) were measured with enzyme-linked immunosorbent assay(ELISA).Results TLR2 mRNA expression level was not significantly different between stimulation group and control group in 18 hours(P >0.05).TLR2 mRNA expression level of stimulation group was significantly higher than that of control group(1.3479±0.0562 vs.1.4259±0.0387,P <0.05) in 24 hours.The MyD88 mRNA expression level of stimulation group was significantly higher than that of control group(1.4140±0.0449 vs.1.6844±0.0426,P <0.05) in 18 hours.The MyD88 mRNA expression level was not statistically significantly different between stimulation group and control group in 24 hours(P >0.05).TLR2 mRNA and MyD88 mRNA expression levels of stimulation group were significantly lower than those of control group(P <0.05) in 72 hours.The concentration of TNF-α,IL-1β and IL-6 for Legionella stimulation group were significantly higher than those of the control group(P <0.05) in 18,24 and 72 hours.Conclusion Our study showed that TLR2 and its related inflammatory cytokines TNF-α,IL-1β and IL-6 can effectively resist Legionella infection and TLR2 mediated innate immunity may be a protective factor for Legionella infection.