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. Author manuscript; available in PMC: 2022 Dec 1.
Published in final edited form as: FEBS J. 2021 Mar 3;288(24):7123–7142. doi: 10.1111/febs.15770

Figure 1. Naïve T cell homeostasis.

Figure 1.

A. Both, naïve CD4+ and naïve CD8+ T cells decrease in absolute numbers with age with the latter decreasing more drastically. B. Naïve T cell replenishment is maintained by thymic output and homeostatic proliferation in neonates. At age 20 years, thymic output has dropped to less than 20% with further decline to <1%; homeostatic proliferation accounts for the majority of naïve T cell generation throughout adulthood. C. The distribution of clonal sizes (illustrated by boxes) widens with age. Occurrences of larger clones in the naïve T cell compartment increase, associated with increased fitness selection over lifetime. D. The number of TCR in the T cell repertoire rapidly increases within the first decade of life and declines with older age. Computer simulations predict that the confidence interval of this decline is large.