The CD8 isoform CD8alphaalpha is not a functional homologue of the TCR co-receptor CD8alphabeta.
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.
Gangadharan
Denise
D
Division of Developmental Immunology, La Jolla Institute for Allergy & Immunology, 10355 Science Center Drive, San Diego, California 92121, USA.
Cheroutre
Hilde
H
D017951:Antigen Presentation / Q000276:immunology; D000938:Antigen-Presenting Cells / Q000276:immunology; D015704:CD4 Antigens / Q000276:immunology*; D016827:CD8 Antigens / Q000276:immunology*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D002454:Cell Differentiation / Q000276:immunology; D005786:Gene Expression Regulation; D015395:Histocompatibility Antigens Class I / Q000276:immunology*; D008213:Lymphocyte Activation / Q000276:immunology*; D020033:Protein Isoforms / Q000276:immunology; D011948:Receptors, Antigen, T-Cell / Q000276:immunology*; D015398:Signal Transduction / Q000276:immunology; D013950:Thymus Gland / Q000276:immunology
D015704:CD4 Antigens; D016827:CD8 Antigens; D015395:Histocompatibility Antigens Class I; D020033:Protein Isoforms; D011948:Receptors, Antigen, T-Cell