Supercentenarian immune cells expand rather than wear out

Clinical takeaway: Immune aging may involve active restructuring, not only decline. 

Some people reach extreme old age without the cancers and cardiovascular disease that define late life for nearly everyone else. Whether their immune systems are simply aging more slowly, or aging differently, has been unclear. 

Supercentenarians, people who live to 110 or beyond, have shown immune profiles that look younger than their chronological age in prior work. A recent small study set out to characterize what that difference actually consists of. 

T cells are often sorted by function. CD4 helpers coordinate the immune response, while CD8 killers destroy infected and malignant cells. CD4 cytotoxic T lymphocytes (CD4 CTLs) do both. They carry the helper marker but arm themselves with granzyme and perforin, and they typically account for less than 5% of circulating T cells. 

These cells show up in chronic infections such as CMV and HIV, can kill tumor cells directly, and clear senescent cells in aging tissue. But what those targets share is persistence; CD4 CTLs accumulate against threats the immune system cannot finish clearing. 

Across three age bands of older adults (70s to 90s), centenarians, and supercentenarians (110 or older), CD4 CTLs made up a median 4.0% of T cells, 9.6%, and 17.6%, respectively. Chronic stimulation of this kind often drives cells toward exhaustion, but these showed none. They were PD-1 negative, with exhaustion-associated genes remaining low. 

Just a few clones did most of the work. The largest clone averaged 33.3% of a donor's CD4 CTLs, and in one centenarian a single clone accounted for 53.8% of these cells. The authors attribute this to repeated encounters with the same target over years, rather than broad immune activation. Similar clonal expansion appeared at every age, so it does not by itself explain the supercentenarian numbers. 

When the team matched those dominant clones against a public T cell receptor database, 32 of the 36 clonally expanded matches came from patients with cancer, most often non-small cell lung cancer. None of the centenarian or supercentenarian donors had a known history of these cancers. The authors treat this as exploratory overlap, not evidence that the cells recognize the same targets. 

The study profiled T cells from 28 Japanese donors, 8 in their 70s to 90s, 10 centenarians, and 10 supercentenarians, using single-cell sequencing that captured gene expression, surface proteins, and receptor sequences from the same cells. 

The pattern suggests the aging immune system narrows its focus rather than simply failing. As thymic output falls and receptor diversity contracts, the repertoire appears to concentrate on the threats that never resolve: latent viruses, senescent cells, and possibly early malignancy. In supercentenarians, that narrowing looks less like depletion than like specialization. 

An abundance of these cells is also not a clear-cut benefit. The same cell population has been implicated in coronary artery disease and multiple sclerosis, and the authors describe these cells as a double-edged sword. 

"Immune aging is not simply a process of decline. The selective expansion of certain T cells suggests that, even in extreme old age, the immune system may continue to adapt to age-related challenges," said first author Kosuke Hashimoto, an associate professor at the University of Osaka in Japan. 

Source: Hashimoto K, et al. (2026 Aug 19) Cell Rep. CD4 CTLs in supercentenarians: Signs of adaptive expansion in healthy aging