Peyman J A, Hammond G L
Department of Surgery, Yale University School of Medicine, New Haven, CT 06510.
J Immunol. 1992 Oct 15;149(8):2675-80.
Trophoblasts do not express MHC class II Ag on their cell surface, but it is not known at which level the regulation of expression of these IFN-gamma-responsive genes occurs. We localized the IFN-gamma R Ag to the trophoblasts of normal human first trimester placenta. As previously shown, treatment with IFN-gamma of short term cultures of placental explants did not induce expression of HLA-DR Ag in trophoblasts. We demonstrated that in situ hybridization with probes for DRA, DRB, and MHC class II-associated invariant chain genes gave no detectable signals for the presence of the corresponding mRNA in cytotrophoblasts or syncytiotrophoblasts of first trimester placenta with or without IFN-gamma. Maternal leukocytes in these placental preparations as well as IFN-gamma-treated HeLa cell control cultures expressed these mRNA. In addition, Northern analysis of RNA isolated from the trophoblast cell line Jar after treatment with IFN-gamma showed that induction of transcription did not occur from the HLA-DRA, HLA-DRB, or invariant chain genes. Jar cells expressed the IFN-gamma R Ag. These data suggest that down-regulation of MHC class II Ag on trophoblasts in the first trimester placenta and in a cell line include a lack of productive intracellular signaling by the IFN-gamma R and maintenance, in a coordinate manner, of low steady state levels of the mRNA encoded by the DRA, DRB, and invariant chain genes.
滋养层细胞在其细胞表面不表达MHCⅡ类抗原，但这些γ干扰素反应性基因的表达调控发生在哪个水平尚不清楚。我们将γ干扰素受体抗原定位到正常人类孕早期胎盘的滋养层细胞。如先前所示，用γ干扰素处理胎盘外植体的短期培养物不会诱导滋养层细胞中HLA-DR抗原的表达。我们证明，用针对DRA、DRB和MHCⅡ类相关恒定链基因的探针进行原位杂交，在有或没有γ干扰素的情况下，孕早期胎盘的细胞滋养层细胞或合体滋养层细胞中均未检测到相应mRNA存在的信号。这些胎盘制剂中的母体白细胞以及经γ干扰素处理的HeLa细胞对照培养物表达这些mRNA。此外，对用γ干扰素处理后的滋养层细胞系Jar分离的RNA进行Northern分析表明，HLA-DRA、HLA-DRB或恒定链基因未发生转录诱导。Jar细胞表达γ干扰素受体抗原。这些数据表明，孕早期胎盘和细胞系中滋养层细胞上MHCⅡ类抗原的下调包括γ干扰素受体缺乏有效的细胞内信号传导，以及以协调的方式维持DRA、DRB和恒定链基因编码的mRNA的低稳态水平。
