How Age Impacts the Immune System

How Age Impacts the Immune System

While it is true that age is nothing but a number and brings gifts like wisdom, there are certain changes to the immune system that still occur. To better understand these changes, it helps to first understand the basics of how immunity works.


What Is Immunity?

Immunity is our body’s defense against foreign organisms (pathogens), infections, and diseases. The immune system is an intricate organization of proteins, cells, tissues, and organs working together and in balance. Immunity can be broadly divided into innate and adaptive immunity.


Innate immunity is the body’s first line of defense against germs entering the body. Innate immunity is also called the “non-specific immune system” because it responds the same way every time to pathogens. The innate immune system works very quickly and is critical during the first 96 hours of exposure to a pathogen. Persons are born with innate immunity, which include physical barriers like the skin, stomach acid, mucus membranes, fever, and non-specific immune cells.


Adaptive immunity, also known as acquired immunity, is involved in fighting pathogens that the body recognizes. There are 2 types of adaptive immunity: passive immunity and active immunity. With passive immunity, antibodies are given to a person. Protection against a disease is immediate but short-lasting.


With active immunity, the immune system is first triggered. After invasion by a pathogen, immune cells called B- and T-lymphocytes (B- and T-cells) become active. It can take 96 hours or longer for these immune cells to respond. What is key about active immunity is that has memory because antibodies and special memory B- and T-cells are formed. Antibodies made during active immunity are long-lasting, sometimes lifelong. If a person becomes re-exposed the same pathogen, the active immune system recognizes it and can respond more quickly. Another way to acquire active immunity is through a vaccine, which mimics a disease, causing our immune system to respond and make antibodies.


Key points

  • There are 2 broad types of immunity: innate immunity and adaptive immunity. Innate immunity is the body’s first defense against disease. Persons are born with innate immunity and non-specific defenses are involved. Adaptive immunity is specific to a pathogen.
  • Passive immunity is a type of adaptive immunity where antibodies are directly given to a person. Protection is immediate but does not last long.
  • Active immunity is another type of active immunity and involves the production of antibodies by our own immune system. It takes longer to develop but protection lasts years and even for life.


How Does Age Affect Immunity?

The gradual breakdown of the immune system due to age is called immune senescence or immunosenescence. The exact mechanisms of immunosenescence are still being studied but researchers know both the innate and adaptive immune systems are affected. Reduced B- and T-cells numbers and diminished functions of tissues and organs involved in immune defense may all play a role in immunosenescence.

As a result of changes in the immune system, older individuals do not respond as well to new or previously encountered pathogens. This may increase their risk of inflammation, infection, and cancer. Additionally, older adults have reduced responses to vaccines. This is why persons over 65 years receive a high-dose flu vaccine. Fluzone High-Dose Quadrivalent vaccine contains a dose four-times as much as Fluzone Quadrivalent.

Studies show that the mortality rate of older patients with acute viral and bacterial infections is three times higher when compared to younger adult patients. Increased viral risk, decreased immune response, and lack of a specific treatment are reasons the aged population has been hit so hard by the coronavirus.

There is currently no known approach that will reverse immunosenescence. However, research continues into understanding the mechanism and rejuvenating cell health. And there are healthy habits that older adults can follow to help keep the body’s defenses strong!


Key points

  • Immune senescence, or immunosenescence, is the gradual breakdown of the immune system due to natural aging
  • The exact reasons why immune senescence occurs are not known but decreased function of immune organs and lower numbers of immune cells may be involved
  • Despite immunosenescence being irreversible, a healthy lifestyle can help keep older adults feeling well and strong



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