People who live past 110 carry an unusual stockpile of a rare cancer-killing immune cell, according to a study published August 19 in Cell Reports by a team at the University of Osaka. The proportion of CD4 cytotoxic T lymphocytes in blood rose with age, and the researchers report that these cells begin to expand around age 100.
The jump appears to start around age 100, not at 110, which is the part of the finding the researchers say is new.
Key takeaways
- The share of CD4 killer T cells climbs with age, and the expansion begins around age 100.
- The cells were heavily cloned, and their receptors resembled those found in people with lung, breast and liver cancer, though nobody in the study had ever had cancer.
- The study cannot show whether these cells help people live longer or simply mark a body that has been fighting something for a long time.
What the study found
The team, led by Kosuke Hashimoto at the University of Osaka, enrolled 28 people, described by Nature as “eight individuals aged 70-90, ten centenarians (people 100-109 years old) and ten supercentenarians.” Japan has only about 150 people aged 110 or older, so a group of ten is a meaningful slice of a very small population.
CD4 cytotoxic T lymphocytes, or CD4 CTLs, are an odd hybrid. Most T cells either coordinate the immune response or kill infected and cancerous cells. These do both.
They were also strikingly clonal, meaning huge numbers of them were identical copies of one another. According to Medical Xpress, “the most prominent clone accounted for an average of 33.3% of CD4 CTLs,” and “in one centenarian’s blood sample, a single clone accounted for 53.8% of their CD4 CTLs.” That pattern is what an immune system looks like when it has been answering the same target over and over.
The researchers then compared the receptor sequences on those clones against a public database. Nearly three dozen matched sequences from people with cancer, most often lung cancer, followed by breast and liver. None of the study participants had a cancer diagnosis.
Dr. Kumar’s take
The headline reads like a longevity superpower. Run the arrow the other way and it reads just as well.
A massive clonal army of T cells aimed at tumor antigens is exactly what you would expect in a body that has spent decades holding back cancer that never became clinically visible. The authors read it the other direction: they conclude that CD4 CTLs “expand and diversify as an adaptation to persistent antigens, potentially contributing to longevity through cancer suppression.” That is a hypothesis, not a demonstration. The cells could just as easily be the receipt for a long fight rather than the reason it was won, and the same blood test would look the same either way.
Hashimoto says so himself. Medical Xpress quotes his caution that the work “does not prove that having an abundance of CD4 CTLs prevents cancer or causes a person to live longer.” David Masopust, a human immunology researcher at the University of Minnesota who was not involved in the study, told NPR: “It’s a great hypothesis. It would demand a lot of further work. It will be very hard to untangle the correlation with any kind of causation.”
Then there is the size. Twenty-eight people, ten of them supercentenarians. That is a signal worth chasing, not a result to act on. It is also a snapshot in time, so nobody watched these numbers rise in the same person.
One more limit that matters: the cells were sampled from blood. Where they went in the body and what they did once they got there is unknown.
What it means for you
Nothing to buy, and nothing to do differently. There is no food, supplement or workout shown to raise your CD4 CTL count, and no test in ordinary clinical use that reports it. Anyone selling you one is ahead of the evidence by a wide margin.
The useful part of this work is not an anti-aging pill. It is the possibility of a blood-based readout of immune surveillance: a way to see whether your immune system is actively engaged with abnormal cells before a tumor is large enough to find. That would be worth having, and this study is nowhere near delivering it.
For now this belongs alongside the rest of the blood chemistry shared by people who live past 100: interesting biology, correlational, and not yet a plan. If you want the deeper question of how tumors stay hidden in the first place, start with why cancer cells choose inefficient energy production.