The CD8 isoform CD8alphaalpha is not a functional homologue of the TCR co-receptor CD8alphabeta

• Published in: Current opinion in immunology Vol. 16; no. 3; pp. 264 - 270
• Main Authors: Gangadharan, Denise, Cheroutre, Hilde
• Format: Journal Article
• Language: English
• Published: England 01.06.2004
• Subjects: Antigen Presentation - immunology; Antigen-Presenting Cells - immunology; CD4 Antigens - immunology; CD8 Antigens - immunology; CD8-Positive T-Lymphocytes - immunology; Cell Differentiation - immunology; Gene Expression Regulation; Histocompatibility Antigens Class I - immunology; Lymphocyte Activation - immunology; Protein Isoforms - immunology; Receptors, Antigen, T-Cell - immunology; Signal Transduction - immunology; Thymus Gland - immunology
• ISSN: 0952-7915; 1879-0372

Although structurally similar, CD8alphabeta and CD8alphaalpha have notably diverted with regard to function. Whereas CD8alphabeta functions as a T-cell receptor (TCR) co-receptor on MHC-class-I-restricted thymocytes and mature T cells, CD8alphaalpha is unable to support conventional positive selection, and can be expressed on T cells independent of the MHC restriction of their TCR. CD8alphaalpha induction is consistent with antigenic stimulation through the TCR, and recent developments have now shown that CD8alphaalpha induced on agonist-triggered immature thymocytes, antigenic-stimulated conventional CD8alphabeta T cells and mucosal T cells mediates the specific modulation of TCR activation signals to facilitate their survival and differentiation into various specialized T-cell subsets.