T-Helper Cell Concentrations Are Elevated in the Blood of People Who Live Exceptionally Long
Why do some people remain exceptionally healthy into their 100s? A Japanese research team led by immunologist Kosuke Hashimoto at Osaka University explored this question by analyzing blood samples from 28 Japanese individuals of different ages. Their focus was on a rare immune cell type: cytotoxic T-helper cells, abbreviated as CD4 CTL.
In most people, CD4 CTL are very scarce, but the data show they become more common with age. Among participants aged 70–90, the median proportion of these cells in blood was around 4%. For those who reached age 100, the share rose to 9.6%, and in people older than 100, it climbed to 17.6%.
- People aged 70–90: about 4% median CD4 CTL in blood.
- Centenarians: 9.6% CD4 CTL.
- Those above 100: 17.6% CD4 CTL.
The cells identified in long-lived participants were highly active and showed no signs of biological exhaustion. These cytotoxic T-helper cells appear when helper T cells sequentially lose the proteins CD27 and CD28. On average, 33% of the CD4 CTL in the blood of long-lived participants were copies of a single original cell; in one participant, that figure reached 50%.
The study results were published in a Cell Press journal on August 20 at 19:28. DOI: 10.1016/j.celrep.2026.117728.
The researchers interpret these findings as evidence that immune-system aging may reflect an organism's strong adaptive capacity. This work opens new avenues for understanding how the immune system ages and how to support the health of older adults. The high concentration of active T-helper cells in long-lived people may indicate an ability to respond effectively to infections and other threats, which could inform future strategies for maintaining immunity in old age. It also provides a foundation for further experiments in gerontology and immunology.
In addition to the findings on T-helper cells, recent research has also highlighted the role of a tiny organ in the chest, which may reveal further insights into longevity. Understanding how various components of the immune system contribute to extended lifespan can provide a more comprehensive view of healthy aging. For more on this intriguing connection, see how the thymus gland relates to longevity.