Senescence-associated β-galactosidase activity accumulates across major lymphocyte lineages during human aging and associates with functional and cognitive decline

While cellular senescence and immunosenescence jointly drive organismal aging, how these two processes interact remains a critical knowledge gap. Here, senescence-associated beta-galactosidase (SA-ß-gal) activity is used to identify a senescence-associated phenotype across major lymphocyte lineages. We examined its overlap with terminal differentiation markers during human aging and explored its association with clinical correlates. Peripheral blood mononuclear cells from 208 Cuban individuals aged 20–104 years were analyzed by spectral flow cytometry. SA-β-gal high lymphocytes exhibited multiple hallmarks of cellular senescence, including increased expression of cell-cycle inhibitors, DNA damage, mitochondrial oxidative stress, and increased production of pro-inflammatory cytokines. Across T, B, and NK cell compartments, SA-β-gal activity was enriched in highly differentiated populations, including CD4 + and CD8 + EMRA T cells, double-negative B cells, and mature cytotoxic NK cells. However, SA-β-gal high cells were also detected in less differentiated subsets. Aging was associated with a progressive increase of the SA-β-gal signature across major lymphocyte lineage, driven by both the expansion of differentiated subpopulations and increase in the frequency of SA-β-gal high cells within subsets among all stages of differentiation. Structural equation modeling revealed associations between senescence-associated immune phenotypes with cognitive decline, reduced functionality, and lower physical robustness in the elderly. Notably, DN B cell SA-β-gal burden remained associated with physical robustness after adjustment for chronological age. SA-β-gal activity accumulates across major lymphocyte lineages, while displaying distinct, lineage-specific kinetics across the lifespan. While traditional T cell aging markers primarily reflect chronological aging across the lifespan, SA-β-gal activity in DN B cells may capture inter-individual differences in physical robustness among older adults. These findings support the integration of senescence-associated immune phenotypes into multidimensional approaches to better distinguish biological from chronological aging.