A novel Fc gamma R-defined, IgG-containing organelle in placental endothelium.
A novel Fc gamma R-defined, IgG-containing organelle in placental endothelium.
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发表时间：
2005
影响因子：
4.4
通讯作者：
T. Takizawa;C. Anderson;J. M. Robinson
中科院分区：
文献类型：
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作者：
T. Takizawa;C. Anderson;J. M. Robinson
IgG从母体循环到胎儿循环的胎盘转移对于胎儿和新生儿免疫至关重要。这个过程需要IgG刺穿胎盘的两个细胞层。IgG穿过第一层（合体滋养层）的转运几乎肯定是由MHC相关的IgG FcR（FcRn）介导的。直到最近，人们才认为第二层（绒毛内皮）通过小窝中的组成性转胞吞作用允许IgG非特异性移动。然而，我们最近发现，绒毛内皮细胞表达一个单独的IgG的FcR，抑制性基序的轴承Fc γ RIIb 2看到最显着的巨噬细胞和作为一个小部分的Fc γ RIIb上表达的B细胞。现在，通过定量显微镜，我们发现Fc γ RIIb 2在绒毛内皮细胞的一个无法识别的可能是新的细胞器中大量表达，与小窝无关。这些Fc γ RIIb 2细胞器中约有一半含有IgG;其余缺乏IgG。大部分（约80%）含IgG的细胞器与Fc γ RIIb相关。没有含IgG的细胞器与小窝蛋白相关。这些发现与Fc γ RIIb介导的IgG跨绒毛内皮转移一致，与小窝无关。
Placental transfer of IgG from maternal circulation to that of the fetus is crucial for fetal and newborn immunity. This process requires that IgG broach two cellular layers of the placenta. IgG transport across the first layer, the syncytiotrophoblast, is almost certainly mediated by the MHC-related FcR for IgG, FcRn. The second layer, the villus endothelium, was until recently thought to allow IgG movement nonspecifically by constitutive transcytosis in caveolae. However, we recently showed that villus endothelium expressed a separate FcR for IgG, the inhibitory motif-bearing Fc gammaRIIb2 seen most notably on macrophages and as a minor fraction of the Fc gammaRIIb expressed on B cells. Now, by quantitative microscopy, we find Fc gammaRIIb2 to be expressed abundantly in an unidentifiable and likely novel organelle of the villus endothelium, unassociated with caveolae. About half of these Fc gammaRIIb2 organelles contain IgG; the remainder lack IgG. The majority fraction (approximately 80%) of IgG-containing organelles is associated with Fc gammaRIIb. No IgG-containing organelles are associated with caveolin. These findings are compatible with Fc gammaRIIb-mediated transfer of IgG across the villus endothelium, independent of caveolae.