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

* Phenotypic distinction imperfect. ^†Data from [3] for total T cells.

Goronzy and Weyand Arthritis Res Ther 2003 5:225   doi:10.1186/ar974