Castellino F, Germain R N
Lymphocyte Biology Section, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
Immunity. 1995 Jan;2(1):73-88. doi: 10.1016/1074-7613(95)90080-2.
Major histocompatibility complex class II molecules bind and present to T cells fragments of protein antigens entering the endocytic pathway. Using normal B lymphoblasts, we have combined metabolic pulse-chase labelling, high resolution organelle fractionation, and immunoprecipitation to examine class II trafficking and antigen loading in a physiological model system. Most newly synthesized class II-invariant chain complexes first entered early endosomes, then accessed multiple discrete endocytic subcompartments cofractionating with late endosomes and immature lysosomes. Invariant chain was removed and peptide-loaded class II molecules appeared in each of these latter distinct organelles. These findings suggest that class II molecules traffic through much of the endocytic pathway, permitting capture of distinct determinants made available under differing conditions of pH and proteolytic activity.
主要组织相容性复合体II类分子结合进入内吞途径的蛋白质抗原片段，并将其呈递给T细胞。我们利用正常B淋巴母细胞，结合代谢脉冲追踪标记、高分辨率细胞器分级分离和免疫沉淀技术，在一个生理模型系统中研究II类分子的转运和抗原加载。大多数新合成的II类分子-恒定链复合体首先进入早期内体，然后进入多个与晚期内体和未成熟溶酶体共分级分离的离散内吞亚区室。恒定链被去除，肽负载的II类分子出现在这些后一种不同的细胞器中。这些发现表明，II类分子通过大部分内吞途径进行转运，从而能够捕获在不同pH值和蛋白水解活性条件下产生的不同决定簇。
