Circulating, soluble forms of major histocompatability complex antigens are not exosome-associated
Circulating, soluble forms of major histocompatability complex antigens are not exosome-associated
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DOI：
10.1002/eji.200636041
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发表时间：
2006-11-01
影响因子：
5.4
通讯作者：
McLellan, Alexander D.
中科院分区：
文献类型：
--
作者：
MacKay, Philippa A.;LeibundGut-Landmann, Salome;McLellan, Alexander D.
体外研究表明，细胞系释放的可溶性 MHC (sMHC) 与称为外泌体的纳米囊泡结合。据认为，外泌体可能代表生物体液中 sMHC I 类和 II 类分子的主要储存库。然而，大多数研究仅限于用细胞系进行的体外测定。我们在此表明，血清或血浆中的 sMHC 在五个方面与外泌体结合的 sMHC 不同：与外泌体相关的 sMHC 相比，循环 sMHC 密度低，表观分子量低 (40-300 kDa)，并且不具有去污剂不稳定的特性。此外，血液中的大多数 MHC II 类亚型和 MHC I 类在物理上并不相连，循环中的 HLA-DR 可以被 HLA-DR α 链细胞内表位特异性的抗体接触到，而该表位被其与细胞膜或外泌体膜的关联所掩盖。最后，利用鼠 MHC II 类 (C2ta) 启动子突变小鼠的转录激活剂，我们发现 sMHC II 类释放到循环中取决于 C2ta pI 启动子，而不是 pIII 或 pIV。这表明优先使用 C2ta 基因的启动子 pI 的骨髓树突细胞和/或巨噬细胞产生循环中发现的大部分 sMHC II 类。
In vitro studies have shown that soluble MHC (sMHC) released by cell lines is bound to nano-vesicles termed exosomes. It is thought that exosomes may represent the major reservoir of sMHC class I and II molecules in biological fluids. However, most studies have been confined to in vitro assays performed with cell lines. We show here that sMHC in the serum or plasma differs from exosome-bound sMHC in five ways: In contrast to exosome-associated sMHC, circulating sMHC is of low density, has a low apparent molecular mass (40-300 kDa) and is not detergent-labile. Moreover, the majority of MHC class II isoforms and MHC class I in blood are not physically linked and circulating HLA-DR is accessible to an antibody specific for the HLA-DR a-chain intracellular epitope, which is masked by its association with cellular or exosomal membranes. Finally, utilizing transcriptional activator of murine MHC class II (C2ta) promoter-mutant mice, we showed that the release of sMHC class II into the circulation is dependent on the C2ta pI promoter, but not pIII or pIV. This suggests that myeloid dendritic cells and/or macrophages, which preferentially use promoter pI of the C2ta gene, produce most of the sMHC class II found in the circulation.