鼠巨细胞病毒感染对小鼠脾细胞IL-12 p35和p40基因转录和表达的影响

Influence of murine cytomegalovirus infection on the transcription and expression of IL-12 p35 and p40 genes in the splenocytes of mice with disseminative infection

目的探讨鼠巨细胞病毒(MCMV)感染对小鼠脾细胞内TH1细胞调控因子白细胞介素-12(IL-12)p35和p40基因转录和表达影响的时序性变化特点。方法制备全身播散型MCMV感染小鼠模型,于感染后3 d、5 d、7 d、10 d和14 d分离小鼠脾细胞,在PHA刺激后用RT-PCR法检测脾细胞内IL-12 p35和p40 mRNA水平时序性变化,ELISA法测定脾细胞培养上清中IL-12 p70和IFN-γ蛋白水平变化。结果模型鼠在感染后第3天IL-12 p70表达显著增高(P<0．05),但第5天后急剧下降,显著低于正常鼠(P<0．05);IFN-γ在感染后第3天增高达峰值(P<0．01),随后逐渐下降,在感染后第10-14天降至正常水平;IL-12 p35 mRNA水平变化与IL-12 p70完全一致;而p40 mRNA则从感染第3天开始持续高水平表达(P<0．01)。结论IL-12 p35 mRNA和IL-12 p70在感染5 d后持续明显下降是感染后期TH1类细胞因子持续低表达、TH1反应受抑制的主要原因之一;感染后IL-12 p40 mRNA持续高水平可能导致拮抗剂(p40)2表达增加,后者可进一步抑制IL-12功能。

Objective To investigate the influence of murine cytomegalovirus （MCMV） infection on the transcription and expression of IL-12 p35 and p40 genes in the splenocytes of mice with disseminative infection. Methods Fifty BALB/c mice were intraperitoneally inoculated with appropriate amount of MCMV Smith strain for establishing the models of disseminative infection, another twenty five mice served as normal controls. At 3 d, 5 d, 7 d, 10 d and 14 d post CMV infection （p. i. ）, splenocytes were prepared by means of routine method and challenged with PHA. The transcription levels of IL-12 p35 and p40 genes of splenocytes were detected with RT-PCR assay and the expression levels of IL-12 p70 and IFN-γ in supernatant of spleen cell culture were determined by double-antibody sandwich ELISA assay. Results The expression of IL- 12 p70 was up to the highest on day 3 p. i. （ P 〈 0.05）, and was persistently suppressed since day 5 p.i. （ P 〈 0.05）. The level of IFN-γ also was the highest on day 3 p.i. （P〈0.01）, then gradually decreased and reached the normal during the period of day 10 to 14 p.i. The dynamic changes of IL-12 p35 gene transcription were completely same as those of IL-12 p70, and IL-12 p40 mRNA was persistently in significantly higher level after infection （ P 〈 0.01 ）. Conclusion Significantly lower levels of IL-12 p70 and IL-12 p35 rnRNA since day 5 p.i. may be the major reason of obviously lower expression of TH 1 cytokines and inhibition of TH 1 reactions during the later period of CMV infection. Persistent higher transcription of IL-12 p40 gene probably leads to the significant rising of the antagonist, IL-12 （p40）2, which could further inhibit the functions of IL-12.