What are T-cells and why do they decline with age?
Over the years your immune system loses some of its strength as the thymus shrinks and fresh T-cells become scarce. There is currently little that can be done about this concretely, but exercise, good sleep and keeping up with vaccinations help maintain your immune defence as well as possible.
T-cells are white blood cells that form the core of your defence against viruses, bacteria and cancer cells. There are broadly two types: helper cells that coordinate the immune system, and killer cells that directly destroy infected or malignant cells. Naive T-cells are 'fresh' ones that have never encountered a pathogen before and stand ready to recognise new threats.
Those fresh T-cells are produced in the thymus, a glandular organ behind the breastbone. As you age, the thymus shrinks and gradually loses its function. The production of new naive T-cells therefore drops considerably with age. This is also reflected in blood: studies in humans show that the proportion of fresh T-cells decreases measurably. At the same time, the diversity of T-cells diminishes. This means your body has fewer and fewer different 'faces' available to recognise new invaders, which limits the quality of your immune defence in later life.
Meanwhile, older, exhausted T-cells accumulate. In people around the age of sixty, an average of 64% of killer T-cells are in an aged state. They can barely divide any longer and are more or less out of service. That is more than was previously thought.
On top of that, a specific group of inflammation-promoting T-cells increases. They secrete a protein called granzyme K, which stokes low-grade chronic inflammation in surrounding cells and tissues. This is seen as a hallmark of the smouldering inflammation associated with ageing. Aged T-cells may therefore also contribute to autoimmune diseases such as rheumatoid arthritis, presumably because the internal regulation of the immune system deteriorates.
Whether this tide can be turned remains largely unknown. An early exploratory study observed that BCG vaccination in people with a specific immunological profile slightly reduced the 'biological age' of T-cells, but that is a single observation without a proven causal relationship. Much more research is still needed here.
Claims are based on human studies, including single-cell RNA research and observational cohorts. No large randomised trials. Causality is plausible but not always proven. One claim (BCG) is explicitly exploratory and associational.
Does your immune system really weaken as you get older, and can you do anything about it?
Your immune system demonstrably weakens with age, but eating healthily and exercising can reduce the smouldering inflammation that accompanies it. It is still too early to rely on drugs targeting senescent cells.
Does your immune system really weaken as you get older?
Your immune system does indeed weaken as you get older, but how quickly that happens varies considerably from person to person. Lifestyle factors play a role in this, although little has yet been proven specifically for humans.
Which factors weaken your immune system?
Several factors demonstrably weaken your immune system: deficiencies in vitamin A, zinc and iron are the best supported, but medical treatments, chronic stress and strenuous exercise also play a role. When using high-dose steroids medically or in the case of an HIV infection, it is advisable to involve your doctor in infection prevention.
Does your immune system age at a different rate than your heart?
Yes, your immune system and heart age at measurably different rates, and an ageing immune system is more strongly associated with a longer lifespan than the heart is. These are associations, not causal evidence, but that is reason enough to take both seriously.
Does the flu shot work less well as you get older?
The flu shot demonstrably works less well in older adults than in younger people, but high-dose and other improved vaccines substantially reduce that disadvantage. Ask your doctor or pharmacist whether you qualify for such an improved vaccine.
Why are older adults more susceptible to influenza?
Older adults are more susceptible to influenza due to a combination of an ageing immune system, chronic diseases, and low-grade background inflammation. Ask your doctor or pharmacist whether, as someone aged 65 or over, you can receive a high-dose influenza vaccine, as it offers better protection than the standard formulation.