Contributions of CD4+, CD8+, and CD4+CD8+ T cells to skewing within the peripheral T cell receptor beta chain repertoire of healthy macaques.

Diversity in the peripheral T cell receptor repertoire of rhesus (Macaca mulatta) and pig-tailed macaques (Macaca nemestrina) has been studied by examining the profile of CDR3 lengths in TCR beta chains. Expressed CDR3 length distribution profiles for individual TCRBV families were obtained from total peripheral blood mononuclear cells (PBMC) and T cell subsets isolated from PBMC. These studies reveal that the T cell receptor repertoire of PBMC from healthy macaques often exhibits skewing in TCRBV family CDR3 profiles. The skewing of TCRBV family CDR3 profiles was evident as discrete expanded length(s) and was detected in up to 50% of the PBMC profiles. Analyses of separated T cell populations demonstrated that the CD8+ T cell subset was responsible for the majority of observed skewing in CDR3 length profiles. However, CD4+ T cells were also shown to contribute to the skewed peripheral PBMC repertoire in these animals. While certain TCRBV families frequently displayed skewed profiles, there was no concordance in the particular CDR3 lengths expanded among the different animals. Furthermore, an additional feature of the peripheral blood of the animals studied was the presence of an unusual population of extrathymic CD4 and CD8+ (double-positive) T cells (up to 9.6% in the PBMC of rhesus macaques). The double-positive T cells could be differentiated from CD4 single-positive and CD8 single-positive T cells by their increased surface expression of LFA-1 and decreased CD62L expression. The percentage of the double-positive T cells was higher in rhesus than pig-tailed macaques and contributed substantially to the peripheral T cell repertoire.