The immune system can be thought of as a complex network of cells and proteins that defends the body against foreign and harmful substances that can potentially make one ill.

The beauty of our immune system is that it cannot only defend the body from noxious substances but also distinguishes self from non-self and potentially eliminates non-self substances from the body.

Why do you need a healthy immune system?

One needs a healthy immune system to be able to launch an immune attack against foreign substances such as:

  • microorganisms (bacteria, virus, fungi etc.);
  • parasites;
  • cancer cells.

There are two leaves of the immune system, the adaptive and the innate immune system. The former one is our first line defense and the latter is usually responsible for clearing the body from invaders. Immunosenescence which is defined as the gradual deterioration of the immune system is caused by the natural aging process and affects the adaptive immune system mostly.

All these important functions of the immune system can be achieved if communications between immune cells and tissues are intact. In the modern world, there has been a lot of research about how aging affects the immune system and a lot of light has been shed on this phenomenon.

As you grow older your immune system does not work well and the communications between immune cells are disrupted. The immune system becomes slower to respond to invaders and thus makes the elderly population more prone to infections.

Evolution of the immune system in humans from infancy to old age

Immune system function varies with age as like any other systems in your body, from when you were a baby to the elderly.

From birth till the first year of life the immune system is underdeveloped this is evident by the susceptibility of the baby to infections. However complete development is seen at the age of 7-8 years.

The immune system function usually peaks around the 20s and gradually starts to decline thereafter with increasing age. The studies have shown that around 45 years of life the immune system is exactly the same as it was in infancy. By the age of 60-65 immune system becomes weaker and there is a high risk of geriatric diseases such as infections and cancer.

How does aging affect the immune system?

The effects of aging on the immune system are basically due to reduced production of immune cells (B and T cells) in the bone marrow and thymus and also a diminished function of mature lymphocytes in secondary lymphoid tissues (lymph nodes and spleen). As a result, elderly individuals do not respond to harmful substances as robustly as the young ones.

Are elderly people immunodeficient?

The truth of the matter is they’re not, they just do not respond well to new or previously encountered aggressors and their immune system responds slower to invaders.

Even though the mechanisms behind the aging immune system are a bit shady, there are some potential mechanisms which have been put forth:

  • decreased production of immune cells;
  • changes in lymphoid hematopoietic stem cells and progenitor cells; these are cells responsible for renewal of immune cells;
  • involution of thymus which is one of the organs that produce immune cells mainly T cells.

As we age this tiny organ in front of the windpipe is replaced with fat and thus loses its ability to produce immune cells.


This can be explained as an accumulation of inflammatory mediators in tissues and this state has a harmful effect on health and contributes to biological aging and age-related diseases (atherosclerosis, Alzheimer’s disease, type 2 diabetes mellitus).

Consequences of the aging immune system

Well with aging, the immune system becomes less effective in the following ways:

  • less able to distinguish self from non-self, making elderly individuals susceptible to autoimmune disorders;
  • immune system responds more slowly to insults;
  • less responsive to vaccinations;
  • slow healing process;
  • the ability to detect and correct cell defects declines. This predisposes to cancer;
  • the inability to clear off some infections particularly viral infections (cytomegalovirus, Epstein Barr Virus and herpes) and these viruses kind of upregulate the aging process.

How do you improve the immune system as you get older

Nowadays due to advances in medicine and science, all the downsides of the aging immune system can be ameliorated. Here are some ways to lessen the lows of immunosenescence:

  • get vaccines recommended by the health care system (for example: flu);
  • exercise regularly, it helps boost the immune system;
  • eat healthy food particularly vegetables, fruits, proteins, etc.

There was one study that showed an important association between poor calorie intake and being underweight in elderly with deficient or poorly functioning dentition.

However other studies in which the diet of the elderly was supplemented (energy source and trace elements) indicated that individuals could produce a greater response to influenza and pneumococcal vaccination:

  • avoid smoking, it weakens the immune system;
  • restrict alcohol intake;
  • lower your stress levels; stress triggers the body to secret stress hormone (cortisol) which fastens the aging process;
  • get enough sleep.

Potential interventions to rejuvenate the aging immune system

The population of elderly people is growing rapidly. And it is estimated that by 2050 elderly people will be more than the young ones. With an aging population comes an increasing need for healthcare services.

We now know the immune system of old people is not so strong and they usually have some chronic conditions such as heart problems, joint diseases, diabetes, hypertension, etc.

But what if age-related diseases that come with the aging immune system (immunosenescence) can be prevented? That would be great right!

Now that we know possible mechanisms associated with the aging immune system, several interventions can be done to reverse the effects of aging on the immune system:

  • improve the functioning of hematopoietic stem cells;
  • restoration of the involuted thymus by means of hormones (eg. growth hormone);
  • enhance the function of T cells.

Even though immunosenescence poses risk to a whole lot of diseases, some simple measures can be done to improve the health of the elderly population most importantly and easy ones are:

  • eat plenty of fruits, vegetables, and whole grains;
  • get at least 30 minutes of exercise most days of the week;
  • get enough sleep;
  • wash your hands;
  • keep up with your vaccinations; almost everyone who's at least 6 months old should get a flu vaccine every year;
  • keep your weight healthy;
  • don't drink too much alcohol;
  • don't smoke.