title: Anti-CD8 antibodies can trigger CD8+ T cell effector function in the absence of TCR engagement and improve peptide-MHCI tetramer staining.
abstract: CD8(+) T cells recognize immunogenic peptides presented at the cell surface bound to MHCI molecules. Ag recognition involves the binding of both TCR and CD8 coreceptor to the same peptide-MHCI (pMHCI) ligand. Specificity is determined by the TCR, whereas CD8 mediates effects on Ag sensitivity. Anti-CD8 Abs have been used extensively to examine the role of CD8 in CD8(+) T cell activation. However, as previous studies have yielded conflicting results, it is unclear from the literature whether anti-CD8 Abs per se are capable of inducing effector function. In this article, we report on the ability of seven monoclonal anti-human CD8 Abs to activate six human CD8(+) T cell clones with a total of five different specificities. Six of seven anti-human CD8 Abs tested did not activate CD8(+) T cells. In contrast, one anti-human CD8 Ab, OKT8, induced effector function in all CD8(+) T cells examined. Moreover, OKT8 was found to enhance TCR/pMHCI on-rates and, as a consequence, could be used to improve pMHCI tetramer staining and the visualization of Ag-specific CD8(+) T cells. The anti-mouse CD8 Abs, CT-CD8a and CT-CD8b, also activated CD8(+) T cells despite opposing effects on pMHCI tetramer staining. The observed heterogeneity in the ability of anti-CD8 Abs to trigger T cell effector function provides an explanation for the apparent incongruity observed in previous studies and should be taken into consideration when interpreting results generated with these reagents. Furthermore, the ability of Ab-mediated CD8 engagement to deliver an activation signal underscores the importance of CD8 in CD8(+) T cell signaling.
authors.affiliation: Cardiff University School of Medicine, University Hospital, Cardiff CF14 4XN, United Kingdom.
authors.forename: Mathew
authors.initials: M
authors.lastname: Clement
authors.forename: Kristin
authors.initials: K
authors.lastname: Ladell
authors.forename: Julia
authors.initials: J
authors.lastname: Ekeruche-Makinde
authors.forename: John J
authors.initials: JJ
authors.lastname: Miles
authors.forename: Emily S J
authors.initials: ES
authors.lastname: Edwards
authors.forename: Garry
authors.initials: G
authors.lastname: Dolton
authors.forename: Tamsin
authors.initials: T
authors.lastname: Williams
authors.forename: Andrea J A
authors.initials: AJ
authors.lastname: Schauenburg
authors.forename: David K
authors.initials: DK
authors.lastname: Cole
authors.forename: Sarah N
authors.initials: SN
authors.lastname: Lauder
authors.forename: Awen M
authors.initials: AM
authors.lastname: Gallimore
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Godkin
authors.forename: Scott R
authors.initials: SR
authors.lastname: Burrows
authors.forename: David A
authors.initials: DA
authors.lastname: Price
authors.forename: Andrew K
authors.initials: AK
authors.lastname: Sewell
authors.forename: Linda
authors.initials: L
authors.lastname: Wooldridge
mesh_terms: D000906:Antibodies / Q000378:metabolism / Q000502:physiology*; D016827:CD8 Antigens / Q000276:immunology*; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology* / Q000378:metabolism*; D002999:Clone Cells; D003602:Cytotoxicity, Immunologic; D015234:HLA-A Antigens / Q000737:chemistry* / Q000276:immunology; D015789:HLA-A2 Antigen; D006801:Humans; D016130:Immunophenotyping; D008024:Ligands; D010455:Peptides / Q000032:analysis / Q000737:chemistry* / Q000276:immunology; D011948:Receptors, Antigen, T-Cell / Q000172:deficiency* / Q000276:immunology / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology; D013194:Staining and Labeling; D020349:Surface Plasmon Resonance
chemical_list: D000906:Antibodies; D016827:CD8 Antigens; C431698:CD8alpha antigen; D015234:HLA-A Antigens; C435939:HLA-A*02:01 antigen; D015789:HLA-A2 Antigen; D008024:Ligands; D010455:Peptides; D011948:Receptors, Antigen, T-Cell