title: Receptor-like nature of class I HLA: endocytosis via coated pits.
abstract: The present investigations show that class I HLA are internalized by macrophage/monocyte type cells. Anti-class I antibody-binding assays show that about 30% of class I Ag present on cell surface are endocytosed within 1 h. Electronmicroscopic investigations reveal that, like other well established receptor molecules, internalization of HLA is mediated by coated pits and coated vesicles. The endocytosed Ag are transferred from endosomes to trans-Golgi reticulum and trans-Golgi cisternae, suggesting recycling of these Ag back to the cell surface. In the presence of phorbol ester tetradecanoyl phorbol acetate, there is a modest increase in the rate of internalization. These results are consistent with the hypothesis that class I Ag on monocytes/macrophages behave like receptor molecules. Malignant transformation of monocytic cells apparently causes the loss of this property of class I Ag.
mesh_terms: D000954:Antigens, Surface / Q000276:immunology / Q000378:metabolism; D001666:Binding Sites, Antibody; D003034:Coated Pits, Cell-Membrane / Q000502:physiology* / Q000648:ultrastructure; D004705:Endocytosis / Q000187:drug effects; D011992:Endosomes / Q000502:physiology*; D006680:HLA Antigens / Q000276:immunology / Q000378:metabolism*; D015395:Histocompatibility Antigens Class I / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D008264:Macrophages / Q000276:immunology / Q000502:physiology / Q000648:ultrastructure; D009000:Monocytes / Q000276:immunology / Q000502:physiology / Q000648:ultrastructure; D011971:Receptors, Immunologic / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D000954:Antigens, Surface; D006680:HLA Antigens; D015395:Histocompatibility Antigens Class I; D011971:Receptors, Immunologic; D013755:Tetradecanoylphorbol Acetate