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Abstract. Dendritic cells (DCs) are associated with the activation and differentiation of T helper (Th) cells. Cluster of differentiation (CD)80 and CD86, the co-stimulatory molecules highly expressed in DCs, have are prominent in promoting the differentiation of Th cells toward Th2 cells. However, little is known about the effect of CD80 and CD86 knockdown on Th1/Th2 cytokine production in mature DCs (mDCs). The aim of the present study was to investigate whether small-interfering RNA (siRNA) could suppress the surface expression of CD80 and CD86 in mDCs. The effects of CD80 and CD86 knockdown in mDCs on Th1/Th2 cytokine expression were examined using an asthmatic murine model. DCs were isolated, separated and cultured in vitro. Flow cytometry was used to examine the expression of CD11c, CD80 and CD86 on the DCs. The DCs were transfected with CD80-and CD86-specific siRNA, while non-siRNA and negative siRNA controls were also designed. Then, the mRNA and protein expression levels of CD80 and CD86 were determined by reverse transcription-quantitative polymerase chain reaction and flow cytometry, respectively. The levels of interferon (IFN)-γ and interleukin (IL)-4 produced by T cells co-cultured with mDCs were measured by enzyme-linked immunosorbent assay. Substantial downregulation of CD80 and CD86 mRNA and protein levels were observed in the mDCs following transfection with siRNA. The level of IFN-γ produced by T cells co-cultured with mDCs was significantly increased in the siRNA group, while IL-4 production was significantly decreased. These results show that specific targeting of CD80 and CD86 with siRNA is able to suppress CD80/CD86 expression and consequently regulate Th1/Th2 cytokine levels by increasing IFN-γ production and decreasing IL-4 levels in an asthmatic murine model.

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