Ohshima K, Nakashima M, Sonoda K, Kikuchi M, Watanabe T
Department of Pathology, School of Medicine, Fukuoka University, Japan.
Clin Exp Immunol. 2001 Mar;123(3):481-6. doi: 10.1046/j.1365-2249.2001.01461.x.
Pregnancy is an immunological balancing act. Trophoblasts do not express MHC class I or II, except HLA-C and G, but express Fas ligand (FasL), which confers immune privilege. RCAS1 (receptor-binding cancer antigen expressed on SiSo cells) has recently been recognized to play a role in immune evasion of the tumour cells. We therefore studied the involvement of RCAS1 and FasL in the infiltration of NK cells by examining the curettaged uterine contents of 20 cases of early stage of pregnancy. The cases were clinically divided into two groups; curettage was performed (A) due to the absence of foetal heart beats, and (B) due to spontaneous uterine bleeding and abortion. In group A, RCAS1 was expressed in the uterine glands and extravillous cytotrophoblasts, as was FasL. Infiltration of NK cells around the uterine glands was scarcely detected. In contrast, in group B, expression of both RCAS1 and FasL was strikingly decreased in both the level of expression and the numbers of RCAS1/FasL-positive cells and massive infiltration of NK cells was frequently detected around the uterine glands. These findings suggest that a reduction in RCAS1 and FasL expression seems to be closely associated with activation and infiltration of maternal NK cells and destruction of uterine glands, resulting in rejection of the foetus. Thus, expression of RCAS1 and FasL in the uterine glands and cytotrophoblasts may play a role in the downregulation of the maternal immune response, thereby maintaining pregnancy at early stage.
妊娠是一种免疫平衡行为。滋养层细胞不表达MHC I类或II类分子，除了HLA - C和G，但表达Fas配体（FasL），这赋予了免疫特权。最近发现，SiSo细胞上表达的受体结合癌抗原1（RCAS1）在肿瘤细胞的免疫逃逸中发挥作用。因此，我们通过检查20例早期妊娠刮宫后的子宫内容物，研究了RCAS1和FasL在自然杀伤细胞浸润中的作用。这些病例在临床上分为两组；刮宫（A组）是因为没有胎心搏动，刮宫（B组）是因为自然子宫出血和流产。在A组中，子宫腺和绒毛外细胞滋养层中均表达RCAS1和FasL。子宫腺周围几乎未检测到自然杀伤细胞浸润。相反，在B组中，RCAS1和FasL的表达在表达水平和RCAS1/FasL阳性细胞数量上均显著降低，并且在子宫腺周围经常检测到大量自然杀伤细胞浸润。这些发现表明，RCAS1和FasL表达的降低似乎与母体自然杀伤细胞的激活和浸润以及子宫腺的破坏密切相关，从而导致胎儿被排斥。因此，子宫腺和细胞滋养层中RCAS1和FasL的表达可能在下调母体免疫反应中发挥作用，从而在早期维持妊娠。
