Lala P K, Kearns M, Colavincenzo V
Am J Anat. 1984 Jul;170(3):501-17. doi: 10.1002/aja.1001700321.
An immune system capable of discriminating between self and nonself evolved in nature long before the appearance of the viviparous mode of pregnancy, which brings maternal cells into a direct physical contact with genetically disparate cells of fetal origin. In the hemochorial type of placentation, the former include cells of the maternal immune system. This article briefly reviews the possible mechanisms that may protect the semiallogeneic conceptus in nature, with special reference to the role of the cells at the fetomaternal interface. We also present some new data on the antigenicity of pre- and postimplantation trophoblast cells and the immunobiology of decidual cells. Systemic changes in the maternal immune system appear to represent homeostatic responses to the presence of a semiallogeneic conceptus, unrelated to its protection; mechanisms for this protection must reside locally at the fetomaternal interface. We find that the lack of immunogenicity of the outer (trophoblast) cells of the preimplantation blastocyst can be explained by a transient disappearance of the major histocompatibility (MHC) antigens on their cell surface. However, following implantation and the formation of the placenta, class 1 MHC antigens reappear on certain classes of trophoblast cells, i.e., labyrinthine and spongiotrophoblast cells of the murine placenta. Similarly, cytotrophoblast cells of the early human placenta exhibit the presence of class 1 MHC antigens. An absence of class 2 MHC antigens despite the presence of class 1 antigens cannot entirely explain the lack of trophoblast immunogenicity. A local immunosuppression mediated by trophoblast cells themselves as well as maternal cells of hemopoietic origin in the decidua remain as a strong possibility. Typical decidual cells appear to play a central role in the maintenance of pregnancy because of their numerous functions: nutritive, endocrine, and immunoregulatory. Our studies reveal that they are descendants of bone-marrow-derived precursors, have unique surface markers recognizable with monoclonal antibodies nonreactive with other hemopoietic cell lineages, and have the ability to abrogate mixed lymphocyte reactions in vitro in a genetically unrestricted manner. Further studies directed at the cells of the fetomaternal interface should provide a better insight into the mode of survival of the nature's most commonplace allograft.
在胎生妊娠模式出现很久以前，自然界就进化出了一种能够区分自身与非自身的免疫系统，而胎生妊娠模式会使母体细胞与源自胎儿的基因不同的细胞直接发生物理接触。在血绒毛膜型胎盘形成过程中，前者包括母体免疫系统的细胞。本文简要回顾了自然界中可能保护半同种异体胚胎的机制，特别提及了胎儿 - 母体界面细胞的作用。我们还展示了一些关于植入前和植入后滋养层细胞抗原性以及蜕膜细胞免疫生物学的新数据。母体免疫系统的全身性变化似乎代表了对半同种异体胚胎存在的稳态反应，与胚胎保护无关；这种保护机制必定存在于胎儿 - 母体界面局部。我们发现，植入前胚泡外层（滋养层）细胞缺乏免疫原性可以通过其细胞表面主要组织相容性（MHC）抗原的短暂消失来解释。然而，植入后胎盘形成时，I类MHC抗原会重新出现在某些类型的滋养层细胞上，即鼠胎盘的迷路和海绵滋养层细胞。同样，早期人类胎盘的细胞滋养层细胞也表现出I类MHC抗原的存在。尽管存在I类抗原，但II类MHC抗原的缺失并不能完全解释滋养层缺乏免疫原性的原因。由滋养层细胞自身以及蜕膜中造血来源的母体细胞介导的局部免疫抑制仍是一种很大的可能性。典型的蜕膜细胞似乎在维持妊娠中起着核心作用，因为它们具有多种功能：营养、内分泌和免疫调节。我们的研究表明，它们是骨髓来源前体细胞的后代，具有独特的表面标志物，可被与其他造血细胞谱系无反应的单克隆抗体识别，并且能够以基因无限制的方式在体外消除混合淋巴细胞反应。针对胎儿 - 母体界面细胞的进一步研究应该能更好地洞察自然界中最常见的同种异体移植的存活方式。
