1. Doubting the TCR coreceptor function of CD8alphaalpha.
- Author
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Cheroutre H and Lambolez F
- Subjects
- Animals, CD3 Complex immunology, CD3 Complex metabolism, CD4 Antigens immunology, CD4 Antigens metabolism, CD8 Antigens genetics, CD8 Antigens immunology, Cell Differentiation, Histocompatibility Antigens Class I immunology, Histocompatibility Antigens Class I metabolism, Humans, Immunologic Memory, Killer Cells, Natural immunology, Killer Cells, Natural metabolism, Lymphocyte Activation, Receptors, Antigen, T-Cell immunology, T-Lymphocyte Subsets metabolism, Thymus Gland immunology, CD8 Antigens metabolism, Receptors, Antigen, T-Cell metabolism, T-Lymphocyte Subsets immunology
- Abstract
"The beginning of wisdom is found in doubting; by doubting we come to question, and by seeking we may come upon the truth." -Pierre Abélard. CD8 is a glycoprotein expressed on hematopoietic cells. Two isoforms of CD8, CD8alphabeta and CD8alphaalpha, have been identified that are distinct in their expression and function. Whereas CD8alphabeta serves as a T cell receptor (TCR) coreceptor to enhance the functional avidity and is constitutively expressed on MHC class I-restricted T cells, CD8alphaalpha marks T cells that are distinct from the conventional thymus-selected and MHC-restricted CD4(+) or CD8alphabeta(+) T cells. Inconsistent with a coreceptor function, CD8alphaalpha decreases antigen sensitivity of the TCR, and it can be transiently or permanently expressed on T cells, regardless of the MHC restriction of the TCR or the presence of conventional coreceptors. Together, these observations indicate that CD8alphaalpha on T cells marks a differentiation stage and that it likely functions as a TCR corepressor to negatively regulate T cell activation.
- Published
- 2008
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