Major histocompatibility complex class II compartments in human B lymphoblastoid cells are distinct from early endosomes.
Major histocompatibility complex class II compartments in human B lymphoblastoid cells are distinct from early endosomes.
复制标题
DOI：
10.1084/jem.182.2.325
复制
发表时间：
1995-08-01
期刊：
影响因子：
--
通讯作者：
Ploegh HL
中科院分区：
文献类型：
--
作者：
Peters PJ;Raposo G;Neefjes JJ;Oorschot V;Leijendekker RL;Geuze HJ;Ploegh HL
在人B类淋巴母细胞系中，大多数主要组织相容性复合体（MHC）II类异二聚体位于细胞表面和内吞区室中，而不变链（Ii）相关的II类分子代表生物合成中间体，主要存在于内质网和高尔基复合体中。为了研究MHC Ⅱ类分子阳性区室的起源及其与早期内体的关系，我们用免疫电镜技术在冰冻切片上研究了人淋巴母细胞样B细胞中MHC Ⅱ类分子和Ii与内吞示踪物的关系。表面免疫球蛋白的交联，随后免疫复合物的短暂内化，并没有改变MHC II类分子的细胞内分布。虽然早期内体被大量标记为交联的免疫球蛋白，但在早期内体中可检测到< 1%的总MHC II类分子。与trans-Golgi网络相关的MHC II类和Ii类阳性结构可以通过内化30分钟后的内吞牛血清白蛋白（BSA）-金缀合物来达到。长时间暴露于BSA-金允许可视化后期内吞隔室，其中观察到Ii的进行性损失：首先内腔部分，然后Ii的细胞质部分逃脱检测，最终形成缺乏Ii的MHC II类阳性隔室（MIIC）。Ii的损失也与从多泡过渡到多层，电子致密MIIC。因此，II类分子所在的细胞内区室（MIIC）是一组异质结构，是内吞途径后期方面的一部分。
In human B lymphoblastoid cell lines, the majority of major histocompatibility complex (MHC) class II heterodimers are located on the cell surface and in endocytic compartments, while invariant chain (Ii)-associated class II molecules represent biosynthetic intermediates which are present mostly in the endoplasmic reticulum and Golgi complex. To investigate the origin of the MHC class II-positive compartments and their relation to early endosomes, the intracellular distribution of MHC class II molecules and Ii in relation to endocytic tracers was studied in human lymphoblastoid B cells by immunoelectronmicroscopy on ultrathin cryosections. Cross-linking of surface immunoglobulins, followed by a brief period of internalization of the immune complexes, did not alter the intracellular distribution of MHC class II molecules. While early endosomes were abundantly labeled for the cross-linked immunoglobulins, < 1% of total MHC class II molecules were detectable in early endosomes. MHC class II- and Ii- positive structures associated with the trans-Golgi network can be reached by endocytosed bovine serum albumin (BSA)-gold conjugates after 30 min of internalization. Prolonged exposure to BSA-gold allowed visualization of later endocytic compartments, in which a progressive loss of Ii was observed: first the lumenal portion, and then the cytoplasmic portion of Ii escaped detection, culminating in the formation of MHC class II-positive compartments (MIIC) devoid of Ii. The loss of Ii also correlated with a transition from a multivesicular to a multilaminar, electron-dense MIIC. The intracellular compartments in which class II molecules reside (MIIC) are therefore a heterogeneous set of structures, part of the later aspects of the endocytic pathway.