Comparison of CD28 expression versus CD95 or CD45RA expression in both CD4 and CD8 T cells.

Freshly isolated PBMCs were stained with the following combinations of FITC-, PE-, and CyChrome-conjugated mAbs: CD95 or CD45RA, CD28, and CD4 or CD8. (A) In both the young and old subjects, 5% probability contour plots of CD28 expression (Y axis) versus CD95 expression (X axis) showed that both CD4 and CD8 T cells were made of 3 different subsets: CD95⁻CD28⁺ (upper-left boxes), CD95⁺CD28⁺ (ungated), and CD95⁺CD28⁻ (lower boxes). In all stainings, CD28⁻ T cells expressed CD95 at lower intensity than the CD28⁺CD95⁺ counterparts. (B) Analysis of CD28 expression (Y axis) versus CD45RA expression (X axis). In both the young and old donors, not all CD45RA⁺ T cells expressed CD28. Within the CD4⁺ T cells, all CD45RA⁺ were CD28⁺ (upper-right box), whereas in the CD8⁺ T cells, CD45RA⁺ T cells comprised both CD28⁺ (upper-right box) and CD28⁻ T cells (lower-right box). Note that the data were obtained using lymphocytes from the same donors as in Figure 1 and 2.