Phenotypic Changes Accompanying Positive Selection of CD4+CD8+ Thymocytes

Eur J Immunol. 1992 Sep;22(9):2367-72. doi: 10.1002/eji.1830220928.


We know little about the way mature CD4 (helper) and CD8 (killer) T cells develop from thymic CD4+CD8+ precursors. Here we show that small but not large CD4+CD8+ cells with high levels of the alpha beta T cell receptor (TcRhigh) result from positive selection. Neither CD4+CD8+ cells with low TcR levels nor large CD4+CD8+ thymocytes with high TcR levels differentiate in vitro. However, small CD4+CD8+ cells with high TcR levels develop in vitro into mature cells by gradually decreasing the surface levels of one or the other co-receptor and acquiring the potential to respond with proliferation to ligation of the TcR. Small CD4+CD8+ cells with high levels of a major histocompatibility complex (MHC) class I-restricted transgenic TcR develop in vitro exclusively into CD4-CD8+ cells while small CD4+CD8+ TcRhigh cells with heterogeneous TcR from various mice yield both CD4 and CD8 T cells. While these experiments are consistent with an instructive model of CD4/CD8 lineage commitment they do not rule out other mechanisms which require multiple TcR-MHC ligand interactions in the generation of mature alpha beta T cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • CD4 Antigens / analysis*
  • CD8 Antigens / analysis*
  • Cell Differentiation
  • Mice
  • Mice, Inbred C57BL
  • Mice, Inbred DBA
  • Phenotype
  • Receptors, Antigen, T-Cell / analysis
  • T-Lymphocytes / immunology*


  • CD4 Antigens
  • CD8 Antigens
  • Receptors, Antigen, T-Cell