Byline: NIC FLEMING
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 -- which is up by a quarter already compared with last year due to the recent cold weather -- 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: 'It's a double whammy. 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' patrols the body and raises 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 that neutrophils from elderly people are around half as effective at killing bacteria compared with those of younger adults.
One important consequence of our immune system becoming frayed around 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, declines from the age of 40. At 60, 16 per cent of those vaccinated within the previous five years were no longer fully protected.
And flu vaccines are only 30 to 40 per cent effective in those aged 65 and over.
Last year, the Government scrapped its programme of pneumonia vaccinations for the over-65s after experts said the protection they offered were poor and did not last long in older people.
A potential new approach is to inject the vaccine into the skin instead of into the tissue below, as this appears to create a better response in the immune system.
CONSTANT SNIFFLES? IT'S A BAD SIGN IT HAS become clear that different people's immune systems age at different speeds. Professor Akbar says: 'Some older people have young immune systems and some young people have …