Ma C, Blum J S
Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis 46202, USA.
J Immunol. 1997 Jan 1;158(1):1-4.
HLA-DM- APC are unable to present soluble Ags to T cells in the context of class II DR molecules. This defect in DM- APC can be overcome by receptor-mediated delivery of Ag into cells. Ag conjugated to ligands for cell surface receptors, such as transferrin or goat anti-human Ig, was processed and presented by DM- T2.DR4 cells. Intracellular processing of Ag conjugates was required, as receptor cross-linking alone did not restore presentation by DM- APC. Ag conjugates targeted by transferrin receptors to endosomes or via surface Ig to endosomal and lysosomal compartments, were each efficiently presented by DM- cells. These Ag conjugates were predominantly localized in light density endosomes in T2.DR4 cells. This study demonstrates that the facilitated uptake and sorting of exogenous Ag by cell surface receptors allow efficient class II-restricted presentation even in the absence of HLA-DM.
HLA - DM - 抗原呈递细胞（APC）无法在II类DR分子的背景下将可溶性抗原呈递给T细胞。DM - APC中的这一缺陷可通过受体介导的抗原递送入细胞来克服。与细胞表面受体配体（如转铁蛋白或山羊抗人Ig）偶联的抗原可被DM - T2.DR4细胞加工并呈递。抗原偶联物的细胞内加工是必需的，因为仅受体交联并不能恢复DM - APC的呈递功能。通过转铁蛋白受体靶向内体或通过表面Ig靶向内体和溶酶体区室的抗原偶联物，均可被DM - 细胞有效呈递。这些抗原偶联物主要定位于T2.DR4细胞的低密度内体中。本研究表明，细胞表面受体对外源抗原的促进摄取和分选使得即使在没有HLA - DM的情况下也能实现高效的II类限制呈递。
