Figure 3.

Shifts by age in naïve T-cell TL distribution and relative frequency (0 to 10) of T-cell clone size (CS) in the population. (a) displays the shift in TL₂₀ distribution (Figure 2a) resulting from age-dependent shortening of 0.03 kb/year. It depicts TL < TL_O (6.4 kb) by blue bars () and TL > TL_O by red bars (). (b) displays relative frequency of CS generated by naïve T-cell clonal expansion corresponding to the categories of TL below or above TL_O. It shows that maximal CS (MCS) of ∼ 10⁶ cells occurs in individuals with naïve T-cell TL > TL_O, while limited CS (LCS) occurs in those with naïve T-cell TL ≤ TL_O. At age 20, naïve T cells of nine out of ten individuals can generate MCS. At age 70, naïve T cells of less than two out of ten individuals can generate MCS, and seven out of ten generate clone sizes that are less than 0.1 MCS. At age 50 the population is approximately equally divided between the MCS and LCS groups.