Objective: To investigate the effects of gene therapy with IL-10 on PTg-induced proliferation of splenocytes and Th1 cytokine production from PTg-stimulated splenocytes. Methods: EAT rats were divided into four groups:group A (PBS+PLL) , group B (pORF+PLL), group C (pORFmIL10+PLL), and group D (pORFmIL10+ MEM). The substances mixed with lipofectamine were injected into the thyroid tissues of rats on the 18th dday after immunization. The rats were sacrificed at the 8th week. In vitro proliferative responses to ConA and different concentration of PTg were measured by culturing 4×105 splenocytes pulsed with 18.SKBq of [3H] thymidine for the final 12h and then harvested for liquid scintillation counting. In vitro splenocytes were cultured with PTg (25 mg/L). Th1 cytokine IFN-γ,TNF-αand IL-2 were detected by ELISA. Results: The proliferative response to PTg was suppressed in group C, compared with that of group A and B (P＜0.05). The levels of IFN-γ,TNF-oand IL-2 in the supernatant of PTg-stimulated splenocytes were 3548.25 ± 779.47 pg/ml, 27.66±10.50 pg/ml and 3617.73± 609.15 pg/ml, respectively,which were much lower in group C than those in group A and B(P＜0.01, P＜0.05, P＜0.001, respectively). Conclusion: IL-10 gene transmission in thyroid tissues could inhibit PTg specific proliferation of splenocytes from EAT rats and the secretion of Thl cytokines from PTg-stimulated splenocytes.