Sparse production but preferential incorporation of recently produced naive T cells in the human peripheral pool.
Level 4 - case-series / case-control
Prospective in vivo isotope labeling kinetic study in human adults combined with mathematical modeling
PubMed 18420820 · doi:10.1073/pnas.0709713105
What was done
Researchers measured in vivo naive and memory T cell turnover using long-term deuterated water (2H2O) up- and down-labeling in adult humans alongside comparative 2H2O labeling in young mice. Mathematical kinetic modeling was applied to the human labeling curves to estimate daily cell production, peripheral half-lives of naive and memory CD4 and CD8 T cells, and the lifespan of recently produced naive T cells (recent thymic emigrants).
What was found
In contrast to young mice which demonstrated high thymic-dependent daily naive T cell production, adult humans exhibited low daily production of naive T cells. Estimated average half-lives in humans were 4.2 years for naive CD4 T cells and 6.5 years for naive CD8 T cells, compared to 0.4 years for memory CD4 T cells and 0.7 years for memory CD8 T cells. The estimated half-life of newly produced naive T cells was substantially longer than these average half-lives, contradicting the existence of a large short-lived recent thymic emigrant pool.
Why it matters
These findings demonstrate that human naive T cell maintenance in adulthood relies primarily on the long-term survival and preferential incorporation of sparse newly generated cells, rather than rapid turnover from high thymic output as seen in mice.
Limits
The abstract does not state the number of human participants or mice studied, nor the age range or sex breakdown of the adult cohort. Kinetic parameters are estimates derived from mathematical modeling fits to isotopic enrichment data rather than direct single-cell tracking.
Cited by
- context Naive T cells have an estimated lifespan of 10 to 15 years in humans.