Figure 1.

Increase in memory T-cell numbers corresponds with higher frequency of hematopoietic stem cells (HSCs). (A) Absolute numbers of HSCs (Lin^−/loSca-1⁺cKit⁺ CD150⁺CD48⁻) in wild-type (WT), TCRα^−/−and Rag2^−/−-OT-I mice (n=6 mice). (B) (Left) Representative FACS plots showing expression of CD44 and CD62L by bone marrow (BM) TCRβ CD4⁺ and TCRβ CD8⁺ T cells in young (top) versus old (bottom) mice. (Right) Representative FACS plots showing expression of CD150 and CD48 by Lin-/loSca-1⁺cKit⁺ (LSKs) of young and old mice; frequency of HSCs (CD150⁺CD48⁻ cells) is indicated. (C) Frequency of naïve (CD44⁻) and total memory (CD44⁺; effector memory and central memory) CD4⁺ and CD8⁺ T cells in total BM cells. (D) Frequency of HSCs in total BM cells in young and old mice (n=6 mice). Graphs show mean±Standard Deviation of each tested group, pooled from 2 independent experiments.