Evaluation of CD45RA⁺CD62L⁺naive T cells in donors of different ages.

Freshly isolated PBMCs were stained with the following combinations of FITC-, PE-, and CyChrome-conjugated mAbs: CD45RA, CD62L, and CD4 or CD8. A representative comparison of 5% probability contour plots from a young (18-year-old) and an old (80-year-old) subject is shown. An electronic gate was set on CD4⁺ or CD8⁺ T lymphocytes as indicated, and expression of CD45RA (X axis) was correlated to CD62L (Y axis). In both the CD4 and CD8 subsets, CD45RA⁺CD62L⁺ (double-positive) naive T cells (upper-right box) were profoundly reduced in the old subject compared with the young subject; within each of these subjects, the percentage of double-positive cells was higher in the CD4 subset than in the CD8 subset. Moreover, within the CD8 T cells, the proportion of CD45RA⁺CD62L⁻ cells (lower-right box) showed an important age-dependent increase.