A striking immune cell pattern emerges around a person?s 100th birthday
 

Single-cell immune profiling found that CD4 cytotoxic T lymphocytes become more abundant around age 100, showing stepwise differentiation and substantial clonal expansion. Ex vivo experiments also revealed cytokine plasticity within individual clones, supporting the hypothesis that these cells adapt to persistent antigens during healthy aging, although their direct role in longevity remains unproven.

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