Clark David A, Keil Anja, Chen Zhiqi, Markert Udo, Manuel Justin, Gorczynski Reginald M
Department of Medicine, McMaster University, Hamilton, Ontario, Canada.
Am J Reprod Immunol. 2003 Sep;50(3):187-95. doi: 10.1034/j.1600-0897.2003.00086.x.
Th1 cytokine-dependent abortions in the CBA x DBA/2 mouse model have been linked to down-regulation of expression of the CD200 (OX-2) 'tolerance' signal on trophoblast and in decidua prior to onset of the abortion process. Abortions could be prevented by administration of a soluble CD200. Is CD200 expressed on trophoblast in successful human pregnancy?
As one cannot easily obtain trophoblasts in large quantities from successful human pregnancies in the first trimester prior to the onset of the abortion process at 6 weeks gestation, we examined as a first step, trophoblast isolated from term placentae (i.e. successful pregnancies). CD9- trophoblasts were isolated by affinity column and stained for intracellular cytokeratin, and surface CD200 using PE-anti-human CD200 monoclonal antibody. mRNA was extracted from CD9+ and CD9- cells and tested by reverse transcription-polymerase chain reaction for CD200 mRNA. CD9- placental cells were separated by velocity sedimentation and test for CD200-dependent suppression of an allogeneic human mixed lymphocyte culture where cytotoxic T cell (CTL) generation, and Thl --> Th2 cytokine production shift were measured.
CD9- but not CD9+ placental cell populations contained cells with mRNA for CD200, both a normal length transcript and a truncated transcript. Flow cytometry showed a CD200+ cytokeratin+ moderate-to-large-sized cell population compatible with trophoblasts and a smaller subset of cytokeratin- cells that expressed CD200 at normal and at high levels. The moderate-sized population proved most potent at inhibiting CTL generation and caused a Th1 --> Th2 cytokine shift. These effects were blocked by monoclonal anti-CD200.
A subpopulation of cytokeratin+ placental trophoblasts express bioactive CD200 able to alter maternal immune responses in a favorable (Th2 > Th1) direction. Two populations of CD200+ small- and medium-small-sized cytokeratin- placental cells remain to be identified. Studies of karyotyped first trimester elective termination and spontaneous miscarriage tissues are needed.
在CBA×DBA/2小鼠模型中，Th1细胞因子依赖性流产与流产过程开始前滋养层和蜕膜中CD200（OX-2）“耐受”信号表达的下调有关。给予可溶性CD200可预防流产。在成功的人类妊娠中，滋养层是否表达CD200？
由于在妊娠6周流产过程开始前的孕早期，很难从成功的人类妊娠中大量获取滋养层细胞，因此我们首先检测了从足月胎盘（即成功妊娠）分离的滋养层细胞。通过亲和柱分离CD9-滋养层细胞，并用抗细胞角蛋白抗体进行细胞内染色，用PE-抗人CD200单克隆抗体进行表面CD200染色。从CD9+和CD9-细胞中提取mRNA，通过逆转录-聚合酶链反应检测CD200 mRNA。通过速度沉降分离CD9-胎盘细胞，并检测其对同种异体人混合淋巴细胞培养的CD200依赖性抑制作用，其中测量细胞毒性T细胞（CTL）的产生以及Th1向Th2细胞因子产生的转变。
CD9-而非CD9+胎盘细胞群体中含有具有CD200 mRNA的细胞，包括正常长度转录本和截短转录本。流式细胞术显示，CD200+细胞角蛋白+的中等至大细胞群体与滋养层细胞相符，还有一小部分细胞角蛋白-细胞在正常和高水平表达CD200。中等大小的细胞群体在抑制CTL产生方面最为有效，并导致Th1向Th2细胞因子转变。这些作用被抗CD200单克隆抗体阻断。
细胞角蛋白+胎盘滋养层细胞亚群表达具有生物活性的CD200，能够将母体免疫反应改变为有利的（Th2>Th1）方向。仍有待鉴定CD200+的中小和中等大小细胞角蛋白-胎盘细胞群体。需要对核型分析的孕早期选择性终止妊娠和自然流产组织进行研究。
