AIM To investigate the effects of tranfection of IL 2R antisense RNA expression plasmids on mouse spleen cells' proliferation in vitro and its possible mechanism. METHODS Spleen cells were transfected with IL 2R antisense RNA eukaryotic expression plasmids using adhesion assisted lipofection method, and then the spleen cells were stimulated by mitogen. Cells' proliferation was tested by tetrazolium salt (MTT) method. IL 2R mRNA and protein expression level were measured by slot blot hybridization assay and flow cytometry method respectively. RESULTS The proliferation of spleen cells was inhibited obviously after transfecting with recombinant plasmids. The inhibitory rate of pcAnti mIL 2Rαβ and pciAnti mIL 2Rαβ transfected group was higher than that of pcAnti mIL 2Rα and pcAnti mIL 2Rβ transfected group; the inhibitory rate of pcAnti mIL 2Rα tranfected group was higher than that of pcAnti mIL 2Rβ tranfected group. No inhibitory effect on the growth of NIH3T3 cells was observed when they were transfected with recombinant plasmids. IL 2R mRNA and protein expression level were decreased in spleen cells after transfection of recombinant plasmids. CONCLUSION IL 2R antisense RNA can efficiently inhibit the proliferation of mouse spleen cells in vitro. IL 2Rαβ chimeric antisense RNA showed higher inhibitory rate than α or β antisense RNA. IL 2Rα antisense RNA was more effective than β antisense RNA. It can be concluded preliminarily that the inhibitory effect of IL 2R antisense RNA was exclusively on the growth of cells functionally expressing IL 2R. The inhibitory effect on the spleen cells proliferation was likely due to the blocking of IL 2R expression by antisense RNA.