Avian CD4 and CD8 interact with a cellular tyrosine protein kinase homologous to mammalian p56lck


  • André Veillette,

    Corresponding author
    1. McGill Cancer Centre, McGill University, Montreal
    2. Department of Biochemistry, McGill University, Montreal
    • McGill Cancer Centre, Room 701, 3655 Drummond Street, Montreal, Canada, H3G 1Y6
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    • Scholar of the Medical Research Council of Canada.

  • Michael J. H. Ratcliffe

    1. Department of Microbiology and Immunology, McGill University, Montreal
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    • Chercheur-Boursier of the Fonds de la Recherche en Santé du Québec.


Functional as well as immunochemical studies have indicated that chicken T lymphocytes express surface antigens homologous to mammalian CD4 and CD8. The results presented in this report demonstrate that the avian CD4 and CD8 homologs are physically associated with a cellular tyrosine protein kinase related to mammalian p56lck. Furthermore, they show that engagement of either avian CD4 or CD8 is associated with a rapid intracellular tyrosine phosphorylation signal, suggesting that the function of these surface molecules may be mediated through alterations of the associated tyrosine protein kinase. Taken together, these findings demonstrate that the associations of CD4 and CD8 with an intracellular tyrosine protein kinase are evolutionarily conserved, further enhancing the likelihood that they are critical for normal immune functions.