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

• Published in: The Journal of immunology (1950) 2001-07, Vol.167 (1), p.270-276
• Main Authors: Denkberg, Galit, Cohen, Cyril J, Reiter, Yoram
• Format: Article
• Language: English
• Subjects: Antibodies, Blocking - metabolism; Antibodies, Blocking - pharmacology; Antigens, Neoplasm - metabolism; beta 2-Microglobulin - antagonists & inhibitors; beta 2-Microglobulin - metabolism; Binding Sites, Antibody - immunology; Binding, Competitive - immunology; CD8 antigen; CD8 Antigens - immunology; CD8 Antigens - physiology; Cell Line; Clone Cells; Down-Regulation - immunology; Half-Life; HLA-A2 Antigen - metabolism; Humans; Oligopeptides - immunology; Oligopeptides - metabolism; Protein Binding - immunology; Receptors, Antigen, T-Cell - antagonists & inhibitors; Receptors, Antigen, T-Cell - biosynthesis; Receptors, Antigen, T-Cell - metabolism; Staining and Labeling; Stereoisomerism; T-Lymphocytes, Cytotoxic - immunology; T-Lymphocytes, Cytotoxic - metabolism; Tumor Cells, Cultured
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.167.1.270

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.