Rare Cytotoxic CD4 T Cells May Help Supercentenarians Defy Cancer and Aging

Researchers analyzing blood from 28 Japanese adults reported that a rare subset of helper T cells—cytotoxic CD4 T cells (CD4 CTLs)—becomes increasingly abundant in people who live past 100 years. The study, published in *Cell Reports* (2026), proposes that these cells could provide enhanced protection against cancer and other age-related cellular threats.

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The investigators measured CD4 CTL proportions across three age groups. In eight participants in their 70s-90s, the median CD4 CTL share was 4 percent. Among ten centenarians, the median rose to 9.6 percent, and in the supercentenarian subgroup it reached 17.6 percent. One participant under 100 years exhibited the highest proportion observed.

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Clonality analysis showed that, on average, about 33 percent of CD4 CTLs were clones of a single original cell; in one centenarian, roughly half of the CD4 CTLs derived from the same progenitor. The cells displayed stepwise differentiation, cytokine plasticity, and active, non-exhausted phenotypes, suggesting adaptive responses to persistent antigens in very old age.

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Immunologist Kosuke Hashimoto of the University of Osaka in Japan emphasized that immune aging is not merely a decline.

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“As we age, abnormal cells, including senescent and cancerous cells, become more common,” — Kosuke Hashimoto, of the University of Osaka in Japan

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If the expansion of CD4 CTLs contributes to reduced cancer incidence among supercentenarians, the findings could inform strategies to bolster immune surveillance in the broader aging population. However, the authors caution that the sample size is small and limited to a single nationality, underscoring the need for larger, more diverse studies before clinical applications can be considered.

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