The Immune System and Aging – In Simple Language

To understand the immune system and aging requires a bit of knowledge about the immune system and its normal functioning. The immune system protects the body from harmful or foreign objects

It is the body’s very own “military brigade” with front-line soldiers, generals, and the rear calvary!

These include bacteria, viruses, fungi, cancer cells and other harmful organisms. A healthy immune system makes cells and antibodies that attack and destroy these harmful entities.

This article explores the immune system and aging, including normal immune system functioning, disorders and causes of weak immune systems in adults.

What is the Normal Function of the Immune System?

The network of biological processes that protect the body against disease is called the immune system. It is made up of two closely interacting systems.

These are an “innate” immune system and an “adaptive” immune system which together detect and wage war on a wide variety of pathogens.

Various pathogens such as viruses, cancer cells, parasitic worms, and objects such as wood or glass splinters (Wikipedia) can invade or penetrate into the body. Fortunately, the immune system can identify these pathogens from other healthy cells.

One of the first responses to infection is inflammation but it can also occur without any known cause.

Immune system cells are produced by the thymus gland, the spleen and other organs. They are then carried through the body by the lymph vessels to the lymph nodes where they are stored and released when needed.

These system cells are involved in regulating several physiological activities in the body by interacting interacting with the endocrine (reproductive) and nervous systems.

Furthermore, they play a key role in the development of the human embryo and help to repair and regenerate tissues.

How Does the Immune System Do its Work?

To make this easy to understand, we will review the sequence of events.

  • A virus or other foreign body infiltrates the body
  • The first line defense responder warrior cells (called the “innate immune system”) act quickly and aggressively. They send out alerts and instructions to other cells and provoke inflammation to start attacking and destroying the virus.
  • The “innate” immune system is also responsible for cleaning up these damaged cells, misfolded proteins and other debris in the body, even when there is no infection to fight.
  • Several days after the innate immune response begins, the “adaptive” immune system of the body starts a second wave of attacks against the invader. This attack is more targeted than the first, methodically destroying cells infected by this specific virus with T-cells.
  • When a T-cell comes across a foreign pathogen, it sends out a signaling device that allows the T-cell to bind to the active form of vitamin D to attack the pathogen.
  • When everything is working correctly, these T cells (associated with Vitamin D) make copies of themselves so that at the height of the infection, the body is swarming with them. At the end of the cleanup, a few of them remain behind in the body to guard against return attacks from the same pathogen.

Weakening of the Immune System – Disorders in Humans

Failures of defense by the body fall into three main categories: immunodeficiency disorders, autoimmune disorders, and hypersensitivity disorders.

1. Immunodeficiency Disorders

Immunodeficiency disorders occur when one or more parts of the immune system are inactive.

Common causes of poor immune function in developed countries are obesity, alcoholism, and drug use, while the most common cause in developing countries is malnutrition resulting from diets lacking sufficient protein.

Furthermore, surgical removal of the thymus gland for whatever reason, results in severe immunodeficiency and a high susceptibility to infection.

An arm affected by psoriasis
Psoriasis on the arm

2. Autoimmune Disorders

These disorders are typically caused by overactive immune responses where the immune system fails to properly distinguish between the body’s own cells and invading cells, and begins to attack part of the body.

Commonly known autoimmune diseases include rheumatoid arthritis, diabetes mellitus type 1, Hashimoto’s thyroiditis and a form of systemic lupus.

3. Hypersensitivity (or Intolerance) Disorders

Undesirable reactions produced by the normally functioning immune system. They include allergies, can overlap with autoimmunity, and develop as an over-reaction of the immune system which may be irritating, uncomfortable, damaging, or sometimes fatal.

Other General Causes of Weak Immune Systems in Adults

There are at least four causes of weak immune systems in adults. These are toxins, unstable oxygen molecules in the body, sleep and hormones.

Toxins in foods and the environment, poor diet and stress can all contribute to a decline in immune system activity. When your immune system is weakened, your body becomes fatigued and cannot prevent or fight infections. In terms of the immune system and aging, it is easy to see why older adults are more prone to infections.

Unstable Oxygen Molecules in the Body: Immune cells can be damaged by unstable oxygen molecules in the body called free radicals, which may be generated in dangerously high numbers by poor nutrition, X-rays, alcohol, cigarette smoke and pollutants.

Hydrogen water is good for the body. This is because active hydrogen in hydrogen water can combine with free radicals to achieve strong penetration, continuously enhance human blood circulation, activate body cells and enhance immunity.

It can also promote digestion and excretion, improve gastrointestinal system, and effectively improve metabolism.

Sleep and Rest: Did you know that the immune system is affected by sleep and rest, and sleep deprivation is detrimental to immune function. Furthermore, the immune response to infection may result in changes to the sleep cycle.

Hormones: Hormones may stimulate, suppress, or regulate the immune system. They play an enhanced role in altering the sensitivity of the immune system in younger adults.

Female sex hormones are known to stimulate both adaptive and innate immune responses. Some autoimmune diseases tend to affect women and their onset often coincides with puberty.

In contrast, male sex hormones such as testosterone appear to be immune suppressing.

Other hormones such as the growth hormone, prolactin and Vitamin D appear to regulate the immune system

The Immune System and Aging – What are the Changes?

As you grow older and with each passing decade, there is diminished functioning of your immune system. It does not work as well as it did before.

Moreover, the changes that occur in your network of immune cells are quite complex, resulting in an altered environment of immunity. (Aging Immune System NY Times)

The following immune system changes may occur and make the system less functional with age:

The Immune System and Aging: Causes Fewer Immune Cells in the Body

The ability of the immune system to respond to pathogens is diminished in both the young and the elderly, with immune responses beginning to naturally decline at around 50 years of age.

The body may heal more slowly because there are fewer immune cells in the body to bring about healing.

Over-Reaction and Increased Inflammation of the Immune System

Older cells throughout the body are believed to change with age, releasing their own inflammatory substances. As a result, even perfectly healthy 65-year-olds usually have higher levels of immune proteins (cytokines).

Consequently, damaged cells and waste appear to outrun the ability of the aging immune system to clear it. This means that your innate immune system becomes overwhelmed and descends into a constant state of alert.

This triggers inflammation in the body while the system is unable to cope with the overwhelm and begins to run out of certain immune cells.

All this inflammation chaos causing an increased state of chronic inflammation is linked to frailty. Older adults with higher levels of it may be more fragile and less mobile.

Furthermore, this inflammatory chaos in an aging body makes it harder for messages sent out by the innate immune system to reach their targets thereby creating a tendency for the immune system to over-react.

The Immune System and Aging: Causes Delayed Response in the Body

The immune system responds more slowly to normal triggers as immune cells diminish in the body. This increases the risk of getting sick. Flu shots or other vaccines may not work as well or protect for as long as expected.

In older adults, the “adaptive” immune system response takes longer to react, while its response efforts are crippled by the presence of inflammatory chaos.

These delays mean that the pathogen has already made many copies of itself by the time the adaptive immune system begins to work properly.

To further complicate this situation, there are fewer new copies of T-cells in older adults.

This is important because these cells play a key role as they are trained to hunt down cells infected with a specific pathogen as part of the adaptive response.

The Immune System and Aging: Causes Development of Autoimmunity

An autoimmune disorder is a disease in which the immune system mistakenly attacks and destroys healthy body cells and tissues.

The Immune System and Aging: Causes Decline in Ability to Detect and Correct Defects

The ability of the immune system to detect and correct cell defects also declines. This can result in an increased risk of cancer.

The Immune System and Aging – How Can You Reduce Your Risks?

You can strengthen your immune system and reduce your risks as you age by doing the following:

  • Get plenty of EXERCISE. Exercise, helps maintain good health by promoting blood circulation and ensuring a plentiful supply of oxygen throughout the body.
  • It does not need to be high impact exercise. Using equipment such as the Total Body Exercise Peddler allows you to conduct low impact exercise sitting down in the comfort of your home.
  • EAT HEALTHY FOODS. Good nutrition keeps your immune system strong.
  • VITAMINS help strengthen the immune system by neutralizing cell-damaging particles. Vitamins A, D, C, E, B6 and B12 should be taken as recommended by your physician.
  • DO NOT SMOKE. Smoking weakens your immune system.
  • LIMIT your intake of alcohol.
  • Look into safety measures to prevent falls and injuries. A weak immune system can slow healing.
  • Get the flu and pneumonia VACCINES, and any other vaccines your health care provider recommends.

Conclusion – The Immune System and Aging

The immune system and aging is an important subject for older adults.

Scientists who study the aging immune system believe that understanding it will eventually provide a clearer window into how the immune system and aging are linked.

This can help explain disease vulnerability, and studies will lead to better strategies for developing vaccines.

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Related Articles


McDevitt MA. Aging and the blood (2017). In: Fillit HM, Rockwood K & Young J, Eds. Brocklehurst’s Textbook of Geriatric Medicine and Gerontology. 8th ed. Philadelphia, PA., Elsevier: Chapter 24.

Tummala MK, Taub DD & Ershler WB. Clinical immunology: immune senescence and the acquired immune deficiency of aging (2017) In: Fillit HM, Rockwood K, Young J, Eds. Brocklehurst’s Textbook of Geriatric Medicine and Gerontology. 8th ed. Philadelphia, PA., Elsevier: Chapter 93.

How the Aging Immune System Makes Older People Vulnerable to Covid-19 (2020) A version of this article appears in print on Sept. 8, 2020, Section D, Page 7 of the New York edition with the headline: Why Older Adults Are Vulnerable to Coronavirus Effect.

Aging Changes in Immunity (2020)

6 thoughts on “The Immune System and Aging – In Simple Language”

  1. Hi Ceci, thank you for your very informative article about aging and the immune system. It is well explained and excellent understandable. I had an autoimmune disease due to food allergy and stress, but I healed myself by completely adjusting my diet and lifestyle. Stress makes us vulnerable and weakens our immunity. Some people who work with many pesticides suffer from a weakened immune system experiencing stress from the pesticides. Gluten and milk products can stress the whole system. But also heavy metals, pathogens, and mental stress. I had a combination of mental stress( enormous work stress) and food allergies.
    You are right; I can completely relate to what you are saying. Leaving smoking and drinking too much alcohol and eating healthy food and exercising is vital for keeping a healthy, strong immune system. It has reset my immune system. Thank you for this excellent post.

    • Hello Sylvia,
      Really glad that you were able to overcome your autoimmune disease due to stress and a food allergy by making changes to your diet and lifestyle. Simple lifestyle changes are very helpful.


  2. Hey Ceci, thanks for sharing this post about the immune system and ageing. I’m not an elderly person, but I will be one day, which is why I like to prepare myself for what is coming. I had very limited knowledge about this topic until I read your post here. All I knew is that the immune system protects us from diseases and the stronger it gets, the longer you live, in theory. Well, I’m going to pay closer attention from now on. Thanks again for sharing and keep up the good work!

  3. Well, as someone marching into their mid-60s this makes for sobering reading. I learned a lot from reading this. In my mind, I had just bundled all immune system issues into a single bucket but now I understand there are important distinctions between lack of functioning, overactive functioning, and wrongly reacting immune systems. Inflammation is one of our big enemies and it seems we should do what we can to reduce it. In recent years during my annual medical checkup, the results have come back with vitamin D deficiencies, and last time my vitamin Bs were so low I had to get a course of injections.
    With the coronavirus raging still out there, and vaccination for me still likely to be months away this is all good information to know and act upon. I guess if there is anything we can do to boost our immune systems then we should as this could be what tips the balance.
    Thanks for sharing this very timely information.
    Best regards

    • Hi Andy, knowledge is definitely power. Too many seniors just don’t understand the many changes happening in their bodies and the necessary adjustments they need to make to keep their bodies functioning efficiently. It has been demonstrated, during this pandemic, that booting one’s immune system (along with other medical guidelines) is particularly helpful, so go for it!



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