Last month, a Russian woman claiming to be the world’s oldest person finally gave up on life, at the reported and somewhat dubious age of 123.
Her son apparently said kindness and a positive attitude were the secrets behind her longevity.
He was probably asked this question by a news reporter.
Every year, when the oldest person in the country or the world has a birthday, newsfolk turn up with cameras and microphones wanting to know why they have lasted so long.
A positive attitude almost always gets a mention – along with not drinking alcohol or smoking or eating fancy foods.
None of these answers satisfy because they give no point of difference to people dying of cancer; plenty of short-lived people have positive attitudes, and plenty are committed to the basics of healthy living.
So why do some people hang on for a long time?
Scientists from the RIKEN Center for Integrative Medical Science (IMS) and Keio University School of Medicine in Japan decided to find out.
Their theory was that supercentenarians (people who live for more than 110 years) probably have immune systems super-charged by a mysterious something that the rest of us don’t have.
Two things support this idea.
Firstly, supercentenarians are extremely rare.
The researchers note that in Japan in 2015 there were more than 61,000 people over the age of 100, but only 146 over the age of 110. (It’s worth noting that Japanese people are long-lived as a matter of course, with life expectancy for women standing at more than 87).
Secondly, studies have found that people who survive beyond 110 are relatively immune to illnesses, such as infections and cancer, during their lifetimes. They simply aren’t bothered by sickness like everybody else.
How they found the mysterious something
According to a statement from the IMS, the scientists used single-cell RNA analysis to investigate circulating immune cells from a group of supercentenarians and younger controls.
They acquired a total of 41,208 cells from seven supercentenarians (an average of 5887 per subject) and 19,994 cells for controls (an average of 3999 per subject) from five controls aged in their fifties to eighties.
They found that while the number of B-cells (white blood cells that produce antibodies) was lower in the supercentenarians, the number of T-cells was approximately the same.
However, the very old folk had very high levels of a relatively rare form of T-cell that are cytotoxic – meaning they can kill other cells. In other words, they have a boosted defence system.
In the supercentenarians, these cytotoxic cells accounted for 80 per cent of all their T-cells – while the younger control group had just 10 to 20 per cent of these immune cells that go by the name CD4.
Here is the clincher
Normally, T-cells with markers known as CD8 are cytotoxic, and those with the CD4 marker are not, so the authors first thought that perhaps CD8-positive cells were increased.
But that turned out to not be the case.
CD4-positive cells generally work by generating cytokines, a category of signalling molecules that mediate and regulate immunity.
But in the supercentenarians CD4 cells had acquired killer status.
When the researchers looked at the blood of young donors, there were relatively few CD4-positive cytotoxic cells, “indicating that this was not a marker of youth but rather a special characteristic of the supercentenarians”.
All from a spooky youth-giving cell from long ago
To look at how these special cells were produced, the scientists examined the blood cells of two supercentenarians in detail, and found that “they had arisen from a process of clonal expansion, meaning that many of the cells were the progeny of a single ancestor cell”.
IMS deputy director Piero Carninci, in a prepared statement said, “We believe that these type of cells, which are relatively uncommon in most individuals, even young, are useful for fighting against established tumours, and could be important for immuno-surveillance”.
“This is exciting as it has given us new insights into how people who live very long lives are able to protect themselves from conditions such as infections and cancer,” he said.