Major histocompatibility complex class II compartments in human and mouse B lymphoblasts represent conventional endocytic compartments
Major histocompatibility complex class II compartments in human and mouse B lymphoblasts represent conventional endocytic compartments
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DOI：
10.1083/jcb.139.3.639
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发表时间：
1997-11-03
影响因子：
7.8
通讯作者：
Geuze, HJ
中科院分区：
文献类型：
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作者：
Kleijmeer, MJ;Morkowski, S;Geuze, HJ
在大多数人类和小鼠抗原呈递细胞中，大多数细胞内主要组织相容性复合体（MHC）II类分子存在于晚期内吞MHC II类隔室（MHC）中，被认为在抗原加工和肽装载中起作用。然而，在小鼠A20 B细胞中，已报道早期含内吞II类囊泡（CIIVs）含有大多数细胞内MHC II类分子，并且还涉及MHC II类-肽复合物的形成。为了解决这一差异，我们已经非常详细地研究了人（6H5.DM）和小鼠（A20. A（B））B细胞系的内吞途径。使用定量免疫电子显微镜冷冻切片的细胞，已脉冲追逐转铁蛋白-HRP或BSA-金作为内吞示踪剂，我们已经确定了多达6个内吞亚室，包括早期MIIC型丰富的不变链，这表明它作为一个重要的入口新合成的MHC II类/不变链复合物的内吞途径。此外，早期MIIC代表了最早的含有MHC II类肽复合物的内吞区室，如使用针对丰富的内源性II类肽复合物的抗体所示。早期的MIIC表现出几个，但不是所有的特点，报告的CIIV和位于下游的早期内涵体。除了那些通常存在于非抗原呈递细胞中的结构外，我们还没有遇到任何特殊的含有II类的内吞结构。因此，我们的研究结果表明，B细胞使用传统的内吞隔室，而不是开发了一个独特的隔室来完成MHC II类呈递。
In most human and mouse antigen-presenting cells, the majority of intracellular major histocompatibility complex (MHC) class II molecules resides in late endocytic MHC class II compartments (MHCs), thought to function in antigen processing and peptide loading. However, in mouse A20 B cells, early endocytic class II-containing vesicles (CIIVs) have been reported to contain most of the intracellular MHC class II molecules and have also been implicated in formation of MHC class II-peptide complexes. To address this discrepancy, we have studied in great detail the endocytic pathways of both a human (6H5.DM) and a mouse (A20.A(b)) B cell line. Using quantitative immunoelectron microscopy on cryosections of cells that had been pulse-chased with transferrin-HRP or BSA-gold as endocytic tracers, we have identified up to six endocytic subcompartments including an early MIIC type enriched in invariant chain, suggesting that it serves as an important entrance to the endocytic pathway for newly synthesized MHC class II/invariant chain complexes. In addition, early MIICs represented the earliest endocytic compartment containing MHC class II-peptide complexes, as shown by using an antibody against an abundant endogenous class II-peptide complex. The early MIIC exhibited several though not all of the characteristics reported for the CIIV and was situated just downstream of early endosomes. We have not encountered any special class II-containing endocytic structures besides those normally present in nonantigen-presenting cells. Our results therefore suggest that B cells use conventional endocytic compartments rather than having developed a unique compartment to accomplish MHC class II presentation.