Single-cell analyses of global cohorts outline determinants of immune aging and link the ratio of GZMK+ to GZMB+ Tem cells to health trajectories

Human immune aging is heterogeneous, with immune responses becoming increasingly variable over the lifespan. Here, we integrated seven large-scale public single-cell peripheral blood mononuclear cell (PBMC) datasets and a newly generated cohort, encompassing 2,609 ostensibly healthy individuals across diverse ages, ancestries, and biological sexes. We identified both conserved and cohort-associated age-associated remodeling across 59 immune populations, together with sex- and ancestry-dependent immune differences. CD8