Halloween is nearly here, and while we might expect to see a few zombies wandering around the neighbourhood, apparently there's another kind of zombie we should know about.
And these ones are already living inside us!
No, they're not wandering around looking for brains, but they are attracting quite a bit of attention from scientists investigating ageing and health.
They're called senescent cells, although researchers sometimes refer to them as zombie cells.
And there's a rather fascinating story behind them.
What exactly are zombie cells?
Throughout our lives, our bodies are constantly repairing and replacing cells.
But sometimes, when cells become damaged or experience certain types of stress, they stop dividing.
They don't necessarily die.
Instead, they remain alive and biologically active, sometimes continuing to release chemical signals that influence the cells around them.
In other words, they've stopped doing their usual job but haven't quite left the building!
And here's where things get interesting.
Not all zombie cells are bad.
Some senescent cells actually perform useful functions, including helping with wound healing and preventing damaged cells from multiplying uncontrollably.
So, despite their rather unfortunate nickname, these cells can play an important protective role.
The problem arises when certain senescent cells accumulate and remain in our tissues longer than they should.
As we age, our immune system can become less effective at clearing them away.
Some of these lingering cells release inflammatory substances that may interfere with surrounding tissues and contribute to age-related health problems.
Apparently, even at the cellular level, knowing when to leave can be important!
Scientists have discovered how some zombie cells hide
Now, here's the particularly interesting research.
In 2026, scientists led by researchers at Cedars-Sinai Health Sciences University in the United States identified a protein called PD-L2 that appears to help some senescent cells avoid being removed by the immune system.
Think of our immune system as the body's security team.
Normally, it can recognise and remove many cells that are damaged or no longer needed.
But researchers discovered that some senescent cells appear to use PD-L2 as a way of avoiding that surveillance.
Rather like a zombie finding a way past the security guards!
The scientists investigated what happened when this protein was absent or blocked in laboratory mice.
And the results were encouraging.
Older mice lacking PD-L2 accumulated fewer senescent cells and showed better insulin sensitivity and grip strength than comparison mice.
Blocking PD-L2 also improved insulin sensitivity in aged mice.
The researchers found evidence that PD-L2 was associated with senescent cells in humans, too.
However, there's an important distinction.
These findings do not mean scientists have discovered a proven anti-ageing treatment for people.
The experimental benefits were demonstrated in mice, and further research is needed to establish whether targeting this protein could safely benefit humans.
Still, it's a fascinating development in our understanding of why some ageing cells remain in the body.
But would we really want to get rid of every zombie?
Here's the unexpected twist.
Probably not!
Remember, some senescent cells are actually useful.
They can contribute to tissue repair and help prevent potentially dangerous cells from continuing to divide.
So simply eliminating every senescent cell isn't necessarily the answer.
Researchers are investigating how to distinguish between cells performing beneficial functions and those contributing to ongoing inflammation or tissue damage.
It's a complicated business.
And it raises an interesting question about ageing.
Perhaps the challenge isn't simply preventing our cells from getting older.
Perhaps it's understanding how our bodies manage the changes that naturally occur with age.
That's a rather different perspective from the endless promises we sometimes see about reversing ageing or turning back the clock.
A little Halloween perspective
I find this research particularly interesting because it reminds us how much we're still discovering about the ageing process.
Even something as seemingly straightforward as an old cell turns out to be considerably more complicated than we might imagine.
Some cells are helping us.
Some may be contributing to problems.
And some apparently have rather sophisticated ways of avoiding eviction!
The science is still developing, but understanding these processes may eventually help researchers develop better approaches to age-related disease.
In the meantime, I don't think we need to start worrying about a zombie invasion inside our bodies.
And we certainly don't need to go looking for ways to eliminate every senescent cell ourselves.
After all, we wouldn't want to evict the wrong zombies!
Happy Halloween from Over 60s Wellness! 🎃🧟♂️
Research references
1. Cedars-Sinai research (2026)
Chaib, S., et al. (2026). Blocking PD-L2 prevents senescent cell accumulation and age-related dysfunction.
Cell Metabolism.
https://doi.org/10.1016/j.cmet.2026.08.014
2. National Institutes of Health (2026)
NIH research establishes new framework for the role of senescence in aging.
