RESUMEN
<p><b>OBJECTIVE</b>To observe the change of activation and proliferation ability of rat T-lymphocytes after suppress ICOS gene expression by RNA interference.</p><p><b>METHODS</b>Four interference sites targeting at rat ICOS gene were designed and four pairs of oligonucleotide fragments were cloned into the pSilencer 4.1-CMV neo plasmid vectors then transfected into rat lymphocytes with cationic liposome. The expression of mRNA and protein of ICOS was detected by RT-PCR and flow cytometry. The alteration of lymphocyte proliferation ability was evaluated by mix lymphocyte reaction, and the secretion levels of IFN-gamma and IL-4 were measured by ELISA procedure.</p><p><b>RESULTS</b>After transfection, the expression of mRNA and protein of ICOS in test groups were lower than that in control groups (P < 0.05). The ability of T-lymphocytes in proliferation was poor and the levels of IFN-gamma and IL-4 were reduced with ICOS gene shut down.</p><p><b>CONCLUSIONS</b>RNA interference plasmid vector can suppress ICOS expression in rat T-lymphocytes significantly, and it may be useful for further study on transplantation immunity tolerance.</p>