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

Curr Opin Immunol. 2004 Jun;16(3):264-70. doi: 10.1016/j.coi.2004.03.015.


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.

Publication types

  • Review

MeSH terms

  • 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


  • CD4 Antigens
  • CD8 Antigens
  • Histocompatibility Antigens Class I
  • Protein Isoforms
  • Receptors, Antigen, T-Cell