Table 1 Parameters of T-cell homeostasis in humans
T-cell population | ||||
|---|---|---|---|---|
CD4+ naive | CD4+ memory | CD8+ naive* | CD8+ memory* | |
Pool size (n) | ~ 1 × 1011 | ~ 1 × 1011 | ~ 5 × 1010 | ~ 5 × 1010 |
Diversity | (2–20) × 106 TCR β-chains, each paired with > 25 α-chains [3, 4]† | (2–20) × 105 TCR β-chains, each paired with 1–2 α-chains [3, 4]† | Not determined | Not determined |
Oligoclonality | None | Infrequent | None | Frequent in the elderly |
Frequency of Ki67+ T cells (%) | ~ 0.2 | 1–2 | ~ 0.3 | ~ 3 |
Daily replacement rate by stable isotope labeling of DNA (%) | ~ 0.1 [25] | ~ 0.8 [87] | ~ 0.1 [25] | ~ 0.9 [87] |
Half-life (days) | ~ 700 | ~ 80 | ~ 700 | ~ 70 |
Daily production rates (n) | 1.5 × 108 | 1.5 × 109 | 0.8 × 108 | 0.8 × 109 |