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London - We’re all familiar with the inevitable signs of ageing – creaky knees, grey hair, and crow’s feet to name a few.
But now scientists say it’s not just our skin and joints that show wear through the years.
Our immune system ages, too – becoming less efficient at warding off bugs.
This process is called immunosenescence, and it even causes our immune system to lose its “memory” and forget it has encountered certain bugs before.
Poor immunity puts you at risk of conditions ranging from norovirus, the winter vomiting bug, to cancer.
But just as some people get grey hair before others, some people’s immune systems deteriorate more rapidly than others.
A person in their 50s could have the immune system of an 80-year-old, for example.
However, research has highlighted methods of turning back the clock.
Here we reveal the latest thinking on the immune system – and how you can stop it ageing…
JABS DON’T WORK AS WELL IF YOU’RE OVER 40
Our immune system protects us from viruses, bacteria and parasites, and consists of many different types of cells that carry out specific jobs – rather like different types of soldiers in an army.
However, an ageing immune system has fewer new recruits to combat unknown invaders, and more battle-weary troops only capable of fighting specific types of enemies they’ve already come across.
Dr Donald Palmer, an immunologist who lectures at Imperial College, London, says: “By the time you reach 65, you don’t have the wide range of cells needed to fight new infections, and those you do have are exhausted.”
A group of immune cells called “naive T-cells” patrol the body and raise the alarm when they find infections.
However, fewer of these are generated as we age because the thymus – a small gland behind the breastbone where they are matured – shrinks from puberty.
Furthermore, our immune system holds a “store” of weapons tailored to the bugs it’s met previously but its “memory” becomes less efficient.
In the same way we may struggle to remember names as we age, the immune system struggles to remember if it has encountered a bacteria or virus before.
Professor Arne Akbar, immunologist at University College, London, says the memory cells – known as “memory T-cells” – are the Dads’ Army of the immune system: “They can protect you but not as well as younger soldiers.”
Other immune cells become less effective, too. For instance, neutrophils, which arrive rapidly at the site of injuries and ingest invaders, tire with age.
Experiments by Professor Janet Lord of Birmingham University show neutrophils from elderly people are half as effective at killing bacteria as those of younger adults.
One important consequence of our immune system becoming frayed at the edges is that vaccines, which stimulate the immune defences, become less effective. A study by Austrian scientists found that effectiveness of tetanus jabs, for example, declined from the age of 40. At 60, 16 percent of those vaccinated within the previous five years were no longer fully protected.
And flu vaccines are only 30 to 40 percent effective in over 65s.
CONSTANT SNIFFLES? IT’S A BAD SIGN
In terms of immune system ageing,
Professor Akbar says
genetic factors may play a role, as may the number of infections you have suffered in your life.
If you are a sickly individual who always seems to be battling a cold then there is a fair chance your immune system is older than you are.
Especially important is whether someone has been infected with cytomegalo-virus (CMV), a member of the herpes virus family that can be passed on by kissing and sex. More than half of adults have it.
Professor Akbar says: “You don’t know you have it but your immune system has to work overtime to combat it.”
Once you’re infected, this virus stays with you until the grave.
Scientists believe CMV ages the immune system because it is constantly expending energy to keep it at bay.
Other conditions lie dormant in the immune system, such as chicken pox, but they don’t seem to have such an ageing effect, as they don’t require the same effort to control.
Other researchers have highlighted the impact of chronic stress.
Each cell contains pieces of coiled DNA called chromosomes. And on the ends of these are protective caps called telomeres – rather like the plastic on the end of shoelaces.
These get shorter each time cells divide. Once they reach a certain length they can’t shorten any more, so the cell dies.
Scientists at the University of California, San Francisco, have shown that women who care for chronically ill children or parents; people with post-traumatic stress disorder; and those abused as children all have shorter immune-cell telomeres.
REINVIGORATE YOUR KILLER CELLS
Although there is no magic pill, scientists have a few suggestions, such as moderate exercise, which boosts the body’s ability to fight off bacterial infections.
A study of adults aged 20 to 70 found exercise was linked with a 29 percent reduction in upper respiratory tract infections, for example.
Maintaining good energy levels helps boost immune responses, so those who are underweight or go on crash diets could find themselves at greater risk.
Immunodeficiency expert Professor Richard Aspinall, of Cranfield University, Bedfordshire, says: “To function properly, the immune system needs a lot of energy.
“It is important to get plenty of energy from your diet, a good range of vitamins, and trace elements like selenium and zinc.”
These boost the effectiveness particularly of natural killer cells.
Beef, sardines, probiotic yoghurt, olive oil, pine nuts, mangoes and pomegranates have high levels of nutrients that aid immune responses, according to the charity Age UK.
DON’T SLEEP TOO MUCH – OR TOO LITTLE
Professor Lord led a study of 150 volunteers aged 65 to 92 who wore devices to record how long they slept at night.
Blood tests showed two types of immune cell functioned better in those sleeping an average seven to eight hours, compared with those who slept six hours or less or 8½ hours or more.
“We found the short sleepers seem to be the most affected,” says Professor Lord, whose work is funded by Age UK.
“Their neutrophils don’t kill bacteria as well, and the natural killer cells show a reduced ability to kill cancer cells.”
Previous work by her team suggests that lack of sleep raises levels of the stress hormone cortisol, which may suppress the immune system.
It is not known why sleeping for more than eight hours affects immune functioning.
You might also want to avoid that night cap.
Too much alcohol can interfere with the ability of immune cells to replicate, studies suggest.
It can also inhibit the ability of natural killer cells to take on cancer cells. – Daily Mail