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Doubting the TCR Coreceptor Function of CD8+/-+/-

Hilde Cheroutre and Florence Lambolez

Immunity 28(2):11 (2008) PMID 18275828

''The beginning of wisdom is found in doubting; by doubting we come to question, and by seeking we may come upon the truth.'' -Pierre Abelard CD8 is a glycoprotein expressed on hematopoietic cells. Two isoforms of CD8, CD8@a@b and CD8@a@a, have been identified that are distinct in their expression and function. Whereas CD8@a@b serves as a T cell receptor (TCR) coreceptor to enhance the functional avidity and is constitutively expressed on MHC class I-restricted T cells, CD8@a@a marks T cells that are distinct from the conventional thymus-selected and MHC-restricted CD4^+ or CD8@a@b^+ T cells. Inconsistent with a coreceptor function, CD8@a@a 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 CD8@a@a on T cells marks a differentiation stage and that it likely functions as a TCR corepressor to negatively regulate T cell activation.

Copyright © 2008 Elsevier Ltd. All rights reserved.

DOI: 10.1016/j.immuni.2008.01.005
Version: za2963e q8zad q8zbe q8zcb q8zda q8ze1 q8zf3 q8zgf

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