What does the thymus do, and can you rejuvenate that organ?
The thymus is indispensable for a well-functioning immune system, but inevitably shrinks with age. How this can be counteracted in healthy people is not yet known; keep an eye on developments in this field, but do not use any supplement or treatment that already claims to rejuvenate the thymus.
The thymus is a small organ behind your breastbone that plays a key role in your immune defence well into later life. This is where so-called T-cells mature: white blood cells that recognise pathogens, keep an eye on tumours, and prevent the immune system from attacking the body's own tissues. The thymus also acts as a quality-control checkpoint: T-cells that would attack the body's own tissues are selected out and destroyed.
Unfortunately, the organ begins to shrink quite early in life. This process continues well into adulthood. The specialised cells that allow T-cells to mature decline in number, and the internal structure becomes disrupted. The result is that fewer and fewer new T-cells are produced as we age. This is probably one of the reasons why older people are more susceptible to infections, have a higher risk of autoimmune diseases, and have an immune system that is less effective at monitoring cancer cells. On top of the gradual shrinkage, the thymus can also shrink acutely as a result of infections, chemotherapy, or severe stress. The organ has some capacity for self-repair, but that recovery is often incomplete.
The question of whether the thymus can be 'rejuvenated' is a serious subject of research, but answers for humans are not yet available. In animal studies, activating certain growth signals leads to a clear increase in thymus size. Researchers are also exploring strategies involving growth factors, cytokines (signalling molecules for the immune system), and tissue engineering to restore function. In people whose immune systems have been largely wiped out, for example after a stem cell transplant or during HIV treatment, researchers see the shrunken thymus as the main bottleneck in immune recovery. However, available treatments for 'ordinary' age-related thymus decline do not yet exist.
When the epithelial cells of the thymus function poorly, this is associated with a greater risk of autoimmune diseases and immune deficiencies. These cells are therefore an attractive target for future therapies. For now, the bottom line is this: rejuvenating the thymus is a promising area of research, but whether and when that will lead to anything useful in healthy people remains unclear.
This answer draws on multiple review articles by experts in the field of thymus biology and immune ageing. The function of the thymus and its age-related shrinkage are well documented and widely recognised. The associations with susceptibility to infection, autoimmunity, and reduced tumour immunity are plausible but have not always been directly proven experimentally in humans. The regeneration strategies come almost exclusively from animal and laboratory research; there is no clinical evidence for their effectiveness in humans.
Can you slow down the ageing of your immune system?
The immune system demonstrably ages, and there are promising avenues for slowing that process, but no single approach has been proven safe and effective in humans. Eating less processed food is the only step you can concretely take right now; everything else requires more research in humans before any conclusions can be drawn.
What does ageing of your immune system mean for your health?
Your immune system ages in measurable ways: it responds less effectively to new threats and maintains a smouldering inflammation that is associated with cardiovascular disease, dementia and cancer. An active lifestyle is the best-supported way to slow that process.
Is zinc useful for my immune system?
Zinc supports your immune system, especially when you have a deficiency, and can help symptoms of a respiratory infection clear up more quickly. It does not make you less likely to fall ill, but recovery is on average faster.
How do I strengthen my weakening immune system?
Reducing chronic stress and ensuring adequate sleep and physical activity are the best-supported ways to strengthen your immune system. Probiotics can offer additional help, but which strain is useful for your situation varies.
Does exercise help your immune system as you get older?
Exercise helps older adults: it lowers mild inflammation in the blood and noticeably reduces the risk of physical frailty. How it works on the deeper ageing of the immune system remains an open question.
Does your immune system really weaken as you get older?
Your immune system demonstrably weakens with age, but vaccinations remain worthwhile and a good diet can limit further decline.