Shih I M, Schnaar R L, Gearhart J D, Kurman R J
Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Placenta. 1997 Nov;18(8):667-74. doi: 10.1016/s0143-4004(97)90008-4.
HNK-1 (Leu-7 antigen or CD57) is a unique carbohydrate moiety found in certain glycosphingolipids and several cell adhesion glycoproteins on the cell membrane. Previous studies have suggested that HNK-1 carbohydrates act as adhesive ligands in cell-cell interactions. Using a monoclonal antibody reactive to the HNK-1 moiety and an immunoperoxidase method on formalin-fixed paraffin-embedded tissue, the expression of the HNK-1 epitope in human placentae was confined to the intermediate trophoblast (IT) in trophoblastic columns. The number of HNK-1 immunoreactive IT cells increased from the proximal to the midportion of the trophoblastic column, and then disappeared at the junction of the column with the basal plate where IT infiltrates the endomyometrium and becomes extravillous IT. Neither cytotrophoblast nor syncytiotrophoblast reacted with the HNK-1 antibody. In hydatidiform moles, HNK-1 immunoreactivity was localized to areas that structurally resembled trophoblastic columns. In contrast, placental site trophoblastic tumours which do not contain structures analogous to trophoblastic columns did not express HNK-1 epitope. Expression of HNK-1 was only rarely observed in choriocarcinomas, being present in less than 5 per cent of trophoblastic cells in two of 13 cases. The murine placenta, which lacks trophoblastic columns, was negative for HNK-1. Thin-layer chromatography immunostaining demonstrated the HNK-1 reactive glycosphingolipids in placental lipid extracts, whereas Western blot analysis from placental protein extract failed to reveal detectable glycoproteins that demonstrated HNK-1 immunoreactivity. In conclusion, the specific localization of HNK-1 reactive glycosphingolipids in trophoblastic columns of the human placenta suggests that the HNK-1 moiety may play an important role in maintaining cohesion between intermediate trophoblastic cells in the trophoblastic columns thereby contributing to the structural integrity of the villi that anchor the placenta to the basal plate.
HNK-1（亮氨酸-7抗原或CD57）是一种独特的碳水化合物部分，存在于某些糖鞘脂和细胞膜上的几种细胞粘附糖蛋白中。先前的研究表明，HNK-1碳水化合物在细胞间相互作用中充当粘附配体。使用对HNK-1部分有反应的单克隆抗体和免疫过氧化物酶方法对福尔马林固定石蜡包埋组织进行检测，发现人胎盘组织中HNK-1表位的表达局限于滋养细胞柱中的中间滋养层细胞（IT）。HNK-1免疫反应性IT细胞的数量从滋养细胞柱的近端到中部逐渐增加，然后在滋养细胞柱与基底板的交界处消失，此处IT浸润子宫内膜并成为绒毛外IT。细胞滋养层细胞和合胞体滋养层细胞均不与HNK-1抗体发生反应。在葡萄胎中，HNK-1免疫反应性定位于结构上类似于滋养细胞柱的区域。相反，不包含类似于滋养细胞柱结构的胎盘部位滋养细胞肿瘤不表达HNK-1表位。HNK-1的表达在绒毛膜癌中很少见，在13例中的2例中，不到5%的滋养层细胞中有HNK-1表达。缺乏滋养细胞柱的小鼠胎盘HNK-1呈阴性。薄层色谱免疫染色显示胎盘脂质提取物中有HNK-1反应性糖鞘脂，而胎盘蛋白提取物的蛋白质印迹分析未能检测到显示HNK-1免疫反应性的糖蛋白。总之，HNK-1反应性糖鞘脂在人胎盘滋养细胞柱中的特异性定位表明，HNK-1部分可能在维持滋养细胞柱中中间滋养层细胞之间的黏附方面发挥重要作用，从而有助于将胎盘锚定在基底板上的绒毛的结构完整性。
