Fig. 3.

Age dampens the steady-state proliferation of CD4⁺ and, to a lesser extent, CD8⁺ RTEs. (A) Peripheral T cells from eight 6-week-old and eight 50- to 60-week-old mice fed BrdU in their drinking water for 8 days were stained for CD4 and CD8 and sorted into four populations: CD4⁺ GFP⁺ (Left, filled histograms), CD4⁺ GFP⁻ (Left, open histograms), CD8⁺ GFP⁺ (Right, filled histograms), and CD8⁺ GFP⁻ (Right, open histograms). (B) Sorted cells were stained with anti-BrdU and analyzed by using the illustrated gates into BrdU^hi, BrdU^low, and BrdU^neg populations. Percentages of cells falling into these populations are shown in representative dot plots for the sorted GFP⁻ CD4⁺ (Left) and CD8⁺ (Right) populations. Cytoplasmic GFP is lost during the procedure. (C) Percentages of BrdU⁺ (BrdU^hi plus BrdU^low) CD4⁺ and CD8⁺ populations that are GFP⁺ and GFP⁻ are shown. Data are representative of three independent experiments.