Average T-cell life spans re-estimated from published labeling experiments in humans. Data from 2 published experiments were used: 9-week ²H₂O labeling in 5 healthy individuals,¹⁰  and 1-week deuterated glucose labeling in 4 healthy individuals.¹³  For each individual, the life span of the indicated cell population was estimated using a single-exponential model (●, closed circles) or a multiexponential model (○, open circles, describing 2 kinetically different subpopulations; the addition of more subpopulations did not change the average turnover rate). Estimates obtained for a single individual using the 2 models are connected by a dashed line (‐‐‐). (A-B) For each individual in the 9-week ²H₂O-labeling experiment, the average life span of CD4⁺ and CD8⁺ memory T cells was estimated using both models. Individual fits of the multiexponential model to the memory T-cell data are shown in supplemental Figure 4. (B) The average life span of total CD4⁺ T cells was re-estimated by fitting the single-exponential model (●, closed circles) or the multiexponential model (○, open circles) to the deuterium-labeling data of individuals labeled with deuterated glucose for 1 week,¹³  or ²H₂O for 9 weeks.¹⁰  For the 9-week labeling experiment, individual fits of the multiexponential model are shown in supplemental Figure 5. For the 1-week glucose-labeling data, both models included a 1-day delay.^17,22