Maintenance of naive CD8 T cells in nonagenarians by leptin, IGFBP3 and T3

Research into the age-associated decline in the immune system has focused on the factors that contribute to the accumulation of senescent CD8 T cells. Less attention has been paid to the non-immune factors that may maintain the pool of naive CD8 T cells. Here, we analyzed the status of the naive CD8 T-cell Population in healthy nonagenarians (>= 90-year-old), old (60-79-year-old), and young (20-34-year-old) subjects Naive CD8 T cells were defined as CD28(+)CD95(-) as this phenotype showed a strong co-expression of the CD45RA(+), CD45RO(-), and CD 127(+) phenotypes. Although there was an age-associated decline in the percentage of CD28(+)CD95(-)CD8 T cells, the healthy nonagenarians maintained a pool of naive CD28(+)CD95(-) cells that contained T-cell receptor excision circles (TREC)(+) cells The percentages of naive CD28(+)CD95(-) CD8 T cells in the nonagenarians correlated with the sera levels of insulin-like growth factor binding protein 3 (IGFBP3) and leptin Higher levels of triiodothyronine (T3) negatively correlated with the accumulation of TREC(-)CD28(-)CD95(+) CD8 T cells from nonagenarians These results Suggest a model in which IGFBP3. leptin and T3 act as non-immune factors to maintain a larger pool of naive CD8 T cells in healthy nonagenarians Published by Elsevier Ireland Ltd.