Biased expression of individual T cell receptor V gene segments in CD4⁺ and CD8⁺ human peripheral blood T lymphocytes

The expression of seven different α and β gene segments of the T cell receptor on normal human CD4⁺ and CD8⁺ T lymphocytes, respectively, was examined using V gene-specific monoclonal antibodies. We found a statistically significant (p < 0.001) bias of the expression of four V gene products towards the CD4⁺ subpopulation. In every individual analyzed, the V_β5.1 gene segment was expressed to a higher degree among CD4⁺ compared to CD8⁺ cells, with a median value of 4.8% among CD4⁺ cells and 1.5% among CD8⁺ cells. There was also a statistically significant skewness in the usage of the V_β6.7, V_β8 and V_β12 gene segments towards the CD4⁺ T cell population, but not as dominating as for the V_β5.1. Lymphocytes from umbilical cord blood showed similar skewed reactivities for the V_β5.1, V_β6.7 and V_β12-specific monoclonal antibodies. Aspects of positive and negative selection, as possible explanations for these findings, are discussed.