Immunosenescence: The Relationship Between Immune Health and Aging

Caitlin Beale, MS, RDN

The average lifespan has increased dramatically over the past century, thanks to advances in medicine and public health. But as we live longer, our bodies become more susceptible to disease and less able to fight infection. This is because our immune system also ages. There’s a name for this process: immunosenescence.

Immunosenescence is a natural process whereby the immune system becomes weaker with age, affecting how well you feel as you move into your older years. The good news is that immunosenescence can be slowed down with lifestyle choices, and it's never too early to start.

This blog post explores the relationship between immune health and aging and what you can do to keep your immune system healthy as you age.

What Is Immunosenescence?

Immunosenescence is a term that refers to the age-related decline in the function of the immune system. It is a natural process that begins in early adulthood and progresses steadily as we age. 

The process of immunosenescence is complex, but overall it leads to a decrease in the number and function of immune cells.

A senescent cell stops dividing and can no longer perform its normal function. These cells accumulate with age and are linked with chronic inflammation, tissue damage, and age-related health conditions because they continue to secrete inflammatory chemicals (more on inflammation and aging below).

How Do Your Immune Cells Change With Age?

Age-related declines in immune function stem from a combination of innate and adaptive immune system alterations. 

Your innate immune system responds first and provides a general immune response. The adaptive immune system kicks in later with antibodies that recognize and attack specific threats. The innate and adaptive immune systems are both needed to effectively respond to infection. 

However, since immunosenescence leads to a decline in the number and function of immune cells, older people have an increased susceptibility to illness and can also take longer to recover when they do get sick.

Immunosenescence and the Innate Immune System

Several key players in your innate immune response become less responsive or don't act as they should as you age. 

Neutrophils, for example, are white blood cells that act as first responders for your immune system. But as we get older, neutrophils aren't able to track down and kill potential pathogens as effectively, or they respond much slower, giving potential pathogens a head start to make you sick.

The function of another type of immune cell called natural killer (NK) cells also changes with age. NK cells are primarily considered part of the innate immune system (although some research suggests that they “remember” similar to adaptive immune cells).

NK cells help clear infection, and their job is to directly kill virally infected cells. However, with age, the function of NK cells declines, and they are less able to protect against these cells.

Immunosenescence and the Adaptive Immune System

Changes to your adaptive immune system affect the cells that make antibodies to recognize and fight specific threats. As we age, the number of these cells declines, as does their ability to remember previous infections.

For example, the production of T cells, specialized cells that recognize and fight viral infections, drops with age. Over the years, T cells learn how to better fight viral infections, but we only get so many “naïve” T cells in our lifetime. So as we age, we can become more susceptible to new diseases. 

Inflammation and Aging

Age-related changes in the immune system aren't only about the ability to fend off infection but also about chronic inflammation. The upregulation of the inflammatory immune response in the body associated with age is called inflammaging. Since many chronic diseases are linked to inflammation, this also contributes to aging and illness. 

Inflammation is a normal response of the immune system. When you're injured or fighting an infection, immune cells release chemicals that cause inflammation. 

Signaling molecules called cytokines alert the immune system that something is amiss, turning up inflammation. The critical part of this process is that inflammation should calm down once the threat is gone.

Inflammaging occurs due to persistent inflammation when the immune system is chronically turned on. This chronic, low-grade inflammation is linked with several age-related diseases and is a significant factor in immunosenescence.

Senescent immune cells are more likely to produce inflammatory molecules, contributing to this chronic, low-grade inflammation. 

Another example concerns macrophages, the immune cells that clean up dead cells and cellular debris. According to a paper from Frontiers in Immunology,aging promotes a shift to more pro-inflammatory macrophages, furthering cytokine production and inflammation levels in the body.

Some research also links inflammation and an overproduction of inflammatory cytokines to increased frailty and mortality in older adults. 

What Influences How the Immune System Changes With Age?

Factors that influence immunosenescence include:

• Nutrition

• Genetics

• Physical activity

• Biological sex

• Previous exposure to infections

Can You Reverse or Slow Down Immunosenescence?

You can't slow down time, but there are some steps you can take that influence immune health and aging now at any age. The science behind immunosenescence and aging is complex. Still, lifestyle can affect how quickly your immune cells age.

Diet and Inflammation

There's a well-established connection between nutrition and immune health, leading researchers to believe nutrition may also play a role in immunosenescence.

For example, the Mediterranean diet, high in fruits, vegetables, olive oil, nuts, and fish, has been associated with a lower risk of chronic diseases. It also happens to be anti-inflammatory and could support lower inflammatory molecules and other markers of inflammation.

The Mediterranean diet also highlights fish, which contain omega-3 fatty acids. Omega-3 fatty acids may help the immune system by supporting reductions in inflammatory cytokine production. They also influence T cell proliferation and other immune cell activity.

Micronutrients and Immune Support

Aging can also impact the ability to absorb certain nutrients, further contributing to immunosenescence. Older adults often eat less, have a reduced appetite, and may have difficulty preparing meals, all of which can influence nutritional status and the health of immune cells.

Micronutrients are essential nutrients that the body needs in small amounts to function properly. Many are necessary for the overall function of your immune system. Supplementing with immune-supporting nutrients like vitamins A, D, C, and zinc can help offset the impact of age-related changes on the immune system.

For example, zinc is necessary for the development and function of immune cells. It can also  help protect cells, including immune cells, from damage. 

Low zinc status influences how well the immune system functions, but supplementing with zinc supports a healthy cellular immune response.

Similar results are seen with vitamin C, which supports healthy immune cells and is shown to reduce age-related oxidative stress.

Vitamin D also plays a role in the function of immune cells. Low vitamin D levels are associated with poor immune health, but supplementing with vitamin D could improve immune function. 

Calorie Restriction and Immunosenescence 

Calorie restriction may be another way to slow down the cellular aging process. Studies suggest that caloric restriction could help preserve immune function and delay the onset of age-related changes by reducing the number of inflammatory cytokines to help minimize the impact of inflammation on the body.

Caloric restriction induces autophagy, the process where old and damaged cells are removed to make way for healthy new cells. In one study, calorie restriction was found to reduce the number of senescent cells or cells that no longer function correctly. 

Since extended calorie restriction is hard for many people to sustain, intermittent fasting has become an alternative to turn on some of the same anti-inflammatory pathways. Intermittent fasting is a pattern of eating that alternates windows of eating with fasting—16 hours of fasting with 8 hours of eating is the most popular—and may prove to be a viable option to support a healthy immune response.

Physical Activity and Immune Health Support

In addition to nutrition, physical activity is another important factor in immunity and aging. Regular exercise is linked to immune health support by reducing inflammation and oxidative stress.

Exercise also helps reduce the number of senescent cells in the body. A study examining the effects of physical activity on aging found that moderate-intensity training preserved the number of naive T cells and reduced senescent T cells.

Reducing Stress Could Impact Immunosenescence

Chronic stress is another factor that can contribute to immunosenescence. When you're stressed, your body releases stress hormones like cortisol. Chronic stress can suppress the immune system, making you more susceptible to infection and illness.

A recent study from the Proceedings of the National Academy of Sciences examining adults over age 50 found that living through trauma, discrimination, and chronic stress were all linked to age-related changes in immune health via T cell function.

There are many ways to manage stress, including exercise, relaxation techniques, and spending time with loved ones. You just have to find what works best for you. Taking time to relax and destress could help reduce stress's impact on the immune system and slow down the aging process.

Final Thoughts on Immune Health and Aging

Immunosenescence is the relationship between immune health and aging. As we age, our bodies undergo changes that can affect the function of our immune system. These changes can make us more susceptible to infection and illness.

Fortunately, there are things we can do to offset the impact of immunosenescence. Eating a healthy diet, getting regular exercise, and reducing stress could help slow down the aging process and preserve the function of your immune system. Additionally, supplementation with high-quality micronutrients could further support your immune cells.

By taking steps to preserve our immune function, we can help to protect ourselves against the effects of aging and stay healthy as we age.