To many, immunosenescence may sound like a far-off threat, but it is something that should concern us all. The decline starts surprisingly early in life, during puberty, and can be accelerated by all kinds of lifestyle factors. People who smoke or who are obese are particularly likely to have an immune system that is older than their chronological years. Being sedentary is another risk factor. This has led to a new concept called immune age. It is similar to biological age , which uses chemical tags progressively added to genes throughout life to measure how far down the trajectory of ageing somebody has travelled, regardless of the number of years on the clock.
Biological age and chronological age are usually quite tightly coupled, but can diverge by as much as 20 years either way. And unlike chronological age, biological age can go down as well as up, usually as a result of deliberate lifestyle changes. Both, it turns out, are also true of immunological age. This way of thinking about the immune system has many uses. Knowing our immune age could help doctors judge how susceptible we are likely to be to illness.
It might also help us all to maintain and strengthen our immune system. For instance, it could be used to validate supposed immune-boosting strategies. Does it affect immune age? If not, think twice.
Until very recently, it was impossible to measure immune age. They then repeated the measurements several times over nine years. What they discovered was that human immune systems follow a predictable trajectory.
Immune age measurement is still new and there is no commercially available test, although the team is working on one. For now, probably the best way to gauge your immune age is to get your biological age tested, because the two seem to be roughly correlated.
Regardless, you don't need to know your immune age to take steps to start lowering it. And it turns out that many of the emerging anti-ageing drugs and strategies do their stuff, at least in part, by arresting or even reversing immunosenescence.
One key approach to keeping our immune age down relates to the fact that as we get older, some of our immune cells start to misbehave. This is especially problematic for a class of immune cells called neutrophils, the most common type of white blood cell. These form part of the innate immune system, the body's first line of defence against infection, and are the border force of the immune system, patrolling tirelessly through the bloodstream on the lookout for harmful bacteria.
When they detect an intruder, they squeeze out of the blood vessel and barrel towards their target, then take it out in one of three ways: engulfing it like Pac-Man, spraying it with deadly chemicals or suicidally disgorging their DNA and throwing it around the invader like a net.
The process by which they tunnel through tissues is called chemotaxis, and it becomes increasingly erratic as we age. Older neutrophils can still detect invaders, but become much worse at hunting them down, often blundering haphazardly through tissue or charging off in the wrong direction.
This is problematic for two reasons. It reduces the speed and efficiency of the defence, giving invaders more time to gain a foothold. It also causes inflammation. Lord has found that the blundering neutrophils cause between two and five times as much damage as their comrades that still know their way. Such friendly fire is a leading cause of inflammaging, the generalised low-level inflammation that creeps throughout our bodies as we age.
But the neutrophil satnav can be reset. The root of the problem is a chronically overactive enzyme involved in directional control. So Lord tracked down some existing drugs that were known to dial down this enzyme. When she gave one of these drugs to older adults, she found that it reset their satnav. What are these miracle drugs? Statins, the ordinary cholesterol-lowering drugs already taken by millions of people.
Turning to real patient data from the University of Birmingham's Queen Elizabeth hospital, Lord found that people admitted to hospital with pneumonia were much less likely to die if they were already taking statins to lower their cholesterol. This staggering result has since been confirmed in a small clinical trial. It is too early to recommend that everybody takes statins as an immune booster, says Lord — she and her team are conducting a bigger clinical trial. The drugs can also have serious side effects.
But now might be a good time to have your cholesterol levels tested, once your local health system has capacity. There is also a drug-free way to rejuvenate your neutrophils: exercise.
In , Lord and her colleagues measured exercise levels and neutrophil migration in older adults. She emphasises that neutrophils aren't antiviral so won't prevent you catching coronavirus or help you beat it, but they will protect you from the real danger, which is pneumonia.
Another class of immune cells that begin to misfire as we age are T-cells. These are pivotal in the adaptive immune response — the more targeted part of the system — but are blunted in two ways by immunosenescence. As with neutrophils, their internal signalling pathways go awry, and they are also inhibited by inflammaging. But there may be a simple way to undo this damage. In animal studies, it has long been known to enhance immune function, but the relevance of this research to humans was overshadowed by studies suggesting that vitamin E supplementation is toxic.
Wu now says this is irrelevant: toxicity only arises at doses double that needed for T-cell rejuvenation. He and his colleagues tested vitamin E in older people — giving half of the residents of a nursing home a small daily dose of vitamin E and the other half a placebo — and found significant differences in the rate of upper respiratory infections.
A bigger clinical trial is in the pipeline, but the evidence is already strong enough that Wu recommends people over 65 routinely take international units IUs of vitamin E. Vitamin D, meanwhile, appears to do the same for the innate arm of the immune system, especially among people living at latitudes where there isn't enough winter sunlight for their skin to synthesise the molecule. Scientists have performed experiments in which volunteers were briefly dunked in cold water or spent short periods of time naked in subfreezing temperatures.
They've studied people who lived in Antarctica and those on expeditions in the Canadian Rockies. The results have been mixed. For example, researchers documented an increase in upper respiratory infections in competitive cross-country skiers who exercise vigorously in the cold, but whether these infections are due to the cold or other factors — such as the intense exercise or the dryness of the air — is not known.
A group of Canadian researchers that has reviewed hundreds of medical studies on the subject and conducted some of its own research concludes that there's no need to worry about moderate cold exposure — it has no detrimental effect on the human immune system.
Should you bundle up when it's cold outside? The answer is "yes" if you're uncomfortable, or if you're going to be outdoors for an extended period where such problems as frostbite and hypothermia are a risk.
But don't worry about immunity. Regular exercise is one of the pillars of healthy living. It improves cardiovascular health, lowers blood pressure, helps control body weight, and protects against a variety of diseases. But does it help to boost your immune system naturally and keep it healthy?
Just like a healthy diet, exercise can contribute to general good health and therefore to a healthy immune system. As a service to our readers, Harvard Health Publishing provides access to our library of archived content.
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Today more than ever, people across the world are practicing gratitude for health while being vigilant about protecting it. Pandemics and viruses aside, there are ways to give your health the right priority it needs no matter what age you are. Strong immunity, while crucial to preventing and fighting illness, is also a key component to living a balanced, happy life.
The habits and practices you can do to support your immunity all lend themselves to a happy, holistic existence. It's the best of both worlds; being strong and healthy to combat disease and illness and enjoying your body for the life it's given you. Your immune system is exactly that, a system. The human body is made up of 11 separate systems that do their independent parts to keep your body running at its most optimal.
The primary purpose of your immune system is to protect against pesky, persistent bacteria that want nothing more than to attack your body, breaking it down to make it more susceptible to injury and illness. Your immune system is the gatekeeper for what gets in and what stays out of your body. Your body shows signs of a strong immune system pretty often. One example is when you get a mosquito bite. The red, bumpy itch is a sign of your immune system at work.
If your immune system did nothing, you would never get over the cold, or anything else for that matter. That too is normal; antibiotics were created for this very reason. The good news is there are many things you can do to keep your immune system strong and healthy.
Living a healthy lifestyle is your single best option to a strong immune system. Every part of your body functions better when it is fueled with healthy foods , a positive environment, and minimal stress.
Sound ideal? Here are some easy tips for a stronger immune system that won't overwhelm you.
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