Lyden T W, Robinson J M, Tridandapani S, Teillaud J L, Garber S A, Osborne J M, Frey J, Budde P, Anderson C L
Department of Internal Medicine, Ohio State University, Columbus, OH 43210, USA.
J Immunol. 2001 Mar 15;166(6):3882-9. doi: 10.4049/jimmunol.166.6.3882.
To evaluate the potential role of human placental endothelial cells in the transport of IgG from maternal to fetal circulation, we studied Fc gamma receptor (Fc gamma R) expression by immunohistology and immunoblotting. Several pan-Fc gamma RII Abs that label the placental endothelium displayed a distribution pattern that correlated well with transport functions, being intense in the terminal villus and nil in the cord. In contrast, the MHC class 1-like IgG transporter, FcRn, and the classical Fc gamma RIIa were not expressed in transport-related endothelium of the placenta. Our inference, that Fc gamma RIIb was the likely receptor, we confirmed by analyzing purified placental villi, enriched in endothelium, by immunoblotting with a new Ab specific for the cytoplasmic tail of Fc gamma RIIb. These experiments showed that the Fc gamma RII expressed in villus endothelium was the b2 isoform whose cytoplasmic tail is known to include a phosphotyrosyl-based motif that inhibits a variety of immune responses. We suggest that this receptor is perfectly positioned to transport IgG although as well it may scavenge immune complexes.
为了评估人胎盘内皮细胞在IgG从母体循环转运至胎儿循环中的潜在作用，我们通过免疫组织学和免疫印迹法研究了Fcγ受体（FcγR）的表达。几种标记胎盘内皮的泛FcγRII抗体呈现出与转运功能密切相关的分布模式，在终末绒毛中表达强烈，而在脐带中则无表达。相比之下，MHC I类样IgG转运体FcRn以及经典的FcγRIIa在胎盘与转运相关的内皮中均不表达。我们推断FcγRIIb可能是受体，通过用一种针对FcγRIIb胞质尾的新型抗体对富含内皮的纯化胎盘绒毛进行免疫印迹分析，证实了这一推断。这些实验表明，绒毛内皮中表达的FcγRII是b2亚型，其胞质尾已知包含一个基于磷酸酪氨酸的基序，可抑制多种免疫反应。我们认为该受体虽可能清除免疫复合物，但非常适合转运IgG。
