Critical role for CD8 in binding of MHC tetramers to TCR: CD8 antibodies block specific binding of human tumor-specific MHC-peptide tetramers to TCR.
There are conflicting opinions about the role that the T cell coreceptors CD4 and CD8 play in TCR binding and activation. Recent evidence from transgenic mouse models suggests that CD8 plays a critical role in TCR binding and activation by peptide-MHC complex multimers (tetramers). Here we show with a human CTL clone specific for a tumor-associated MHC-peptide complex that the binding of tetramers to the TCR on these cells is completely blocked by anti-human CD8 Abs. Moreover, the staining of CTLs with specific MHC-peptide tetramers simultaneously with anti-CD8 Abs was completely blocked with three different anti-CD8 Abs. This blockage was mediated by anti-CD8 Abs but not anti-CD3 Abs and was dose dependent. The blocking effect of the anti-CD8 Abs was attributable to directly inhibiting tetramer binding and was not attributable to Ab-mediated TCR-CD8 internalization and down-regulation. Our results have important implications in TCR binding to MHC-peptide tetramers. MHC-peptide tetramers are widely used today in combination with anti-CD8 Abs for the phenotypic analysis of T cell populations and in the study of T cell responses under various pathological conditions such as infectious diseases and cancer. Our results indicate that also in the human system CD8 plays a critical role in the interaction of MHC-peptide multimers with TCR.
Denkberg
G
G
Faculty of Biology, Technion-Israel Institute of Technology, Haifa, Israel.
Cohen
C J
CJ
Reiter
Y
Y
D019138:Antibodies, Blocking / Q000378:metabolism / Q000494:pharmacology*; D000951:Antigens, Neoplasm / Q000378:metabolism*; D001666:Binding Sites, Antibody / Q000276:immunology*; D001667:Binding, Competitive / Q000276:immunology; D016827:CD8 Antigens / Q000276:immunology* / Q000502:physiology; D002460:Cell Line; D002999:Clone Cells; D015536:Down-Regulation / Q000276:immunology; D015789:HLA-A2 Antigen / Q000378:metabolism*; D006207:Half-Life; D006801:Humans; D009842:Oligopeptides / Q000276:immunology / Q000378:metabolism*; D011485:Protein Binding / Q000276:immunology; D011948:Receptors, Antigen, T-Cell / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000378:metabolism; D013194:Staining and Labeling; D013237:Stereoisomerism; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology / Q000378:metabolism; D014407:Tumor Cells, Cultured; D001613:beta 2-Microglobulin / Q000037:antagonists & inhibitors / Q000378:metabolism*
D019138:Antibodies, Blocking; D000951:Antigens, Neoplasm; D016827:CD8 Antigens; D015789:HLA-A2 Antigen; D009842:Oligopeptides; D011948:Receptors, Antigen, T-Cell; D001613:beta 2-Microglobulin