Surface appearance and instability of empty H-2 class I molecules under physiological conditions.
Recent evidence suggests that endogenously produced antigenic peptides are required for assembly of major histocompatibility complex class I chains with beta 2-microglobulin and transport to the cell surface. The RMA-S mutant cells are thought to be defective in intracellular peptide loading to class I molecules and, therefore, devoid of class I surface expression. Here we report that at physiological temperature (37 degrees C) "empty" class I molecules appear at the cell surface of RMA-S cells where they can be trapped with H-2 antibodies. In the absence of the stabilizing ligand, the class I molecules rapidly alter their conformation but remain at the cell surface as demonstrated with a rabbit antiserum. Such denatured H-2 molecules can also be found on normal wild-type RMA cells. However, their amount is strongly reduced after culture of RMA cells with a class I binding peptide. These findings indicate that empty class I molecules appear at the surface not only on mutant but also on normal cells, suggesting that in normal cells the supply with peptides is limited.
Ortiz-Navarrete
V
V
Institute of Immunology and Genetics, German Cancer Research Center, Heidelberg.
Hämmerling
G J
GJ
D000818:Animals; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D006183:H-2 Antigens / Q000378:metabolism*; D066298:In Vitro Techniques; D016399:Lymphoma, T-Cell; D051379:Mice; D010455:Peptides / Q000378:metabolism; D011489:Protein Denaturation; D013601:T-Lymphocytes / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D001613:beta 2-Microglobulin / Q000378:metabolism
D006183:H-2 Antigens; D010455:Peptides; D001613:beta 2-Microglobulin