Abstract: Objective : To explore the effects of Sterigmatocystin (ST) on TAPland LMP2 expres-sion of human peripheral blood mononuclear cells ( HPBMc)in vitro. Methods : The expressions ofTAP1 and LMP2 of HPBMc in vitro after ST treatment at five different concentration (0.125mg/L,0.25mg/L, 0.5mg/L, lmg/L, 2mg/L) were studied with RT-PCR method and flow cytometry (FCM)re-spectively. Results : The effects of ST on TAP1 expressions of HPBMc 24 hrs after ST treatment showedthat mRNA expressions in relatively lower ST concentration (0.125mg/L, 0.25mg/L) groups were higherthan that of control group, while at relatively higher concentration (0.5mg/L,1mg/L and 2mg/L) groups,especially those in ST 1mg/L and 2mg/L groups, were lower than that of control. FCM quantitative anal-ysis showed that at protein level, TAP1 expression (as expressed by FI) of HPBMc arelatively lowconcentration were lower than that of control, but no statistical significance was found, while those of relatively higher ST concentration groups were all significantly lower than that of control (P<0.05). Atthe concentration range from 0.125mg/Lto 1mg/L, the expressions of LMP2 of HPBMc in ST treatmentgroups at both mRNA and protein level were all significantly higher than that of the control. Conclu-sion : The effect of ST onTAP1 mRNA and protein expression of HPBM cin vitro was different as STconcentration changed, while ST could ncreaseLMP2 expression of HPBMc at both mRNA and proteinlevel dose-dependently.