What Is Immunosenescence and How Aging Impacts the Immune System

4.30.2025 0 comments

Author: Trisha Houghton, CNS, ASIST

Our immune systems are our bodies’ natural defense against invading pathogens and toxins. They are made up of trillions of cells that activate upon detecting dangers both internal and external, and neutralize those threats to ensure our bodies remain healthy and function optimally.

Unfortunately, as we age, immune function begins to decline, leading to greater susceptibility to disease and infection later in life.

This deterioration is called immune senescence, or immunosenescence, and it’s a problem that may affect us all sooner or later—unless we take active steps to combat it.

In this post, we’ll examine what immunosenescence is, specifically how our immune system starts to shut down as a natural side effect of aging. We’ll look at how the aging of our immune systems can affect our health and what the long-term consequences are.

But keep reading, because we’ll also spend plenty of time looking at ways you can counteract the effects of immunosenescence through your lifestyle: diet, exercise, and daily living habits.

This post will be a game-changer for your immune system health—not just now, but for the rest of your life!

What is Immunosenescence?

Immunosenescence is described as “a progressive remodeling of immune functioning during aging” or “the gradual deterioration of the immune system, brought on by natural age advancement.”

To put it simply, our bodies become less effective at responding to pathogens, germs, and toxins. They also become less efficient at neutralizing and eradicating these threats. As a result, we are at greater risk of disease, illness, and infection because of the increased cellular senescence of immune cells.

This age-related immune decline is not unique to humans. It’s found in a wide range of both long- and short-lived species, including monkeys, mice, and marsupials. It’s one of the most common contributors to morbidity and mortality among elderly humans and animals.

How the Immune System Works

To understand how the immune system deteriorates as a result of advancing biological and chronological aging, you first need to understand how it works.

The immune system can be divided into two types of immunity: innate and adaptive immunity.

The innate immune system is your body’s first line of defense.

Your skin is part of the innate immune system, a solid barrier to keep out pathogens and germs. If those threats enter your body through your mouth, eyes, or nose, there is mucus and tears to act as a secondary defense.

However, many pathogens get past those initial defenses—such as through wounds, or via the food you eat and water you drink. As these pathogens affect the cells, their presence will trigger first the inflammatory response (swelling) to prevent their spread and neutralize them until white blood cells (leukocytes) can envelop, “digest”, and eliminate them.

Enzymes in your bloodstream also activate as part of the innate immune response. They mark the germs as targets, destroy the bacterial cell walls, and destroy the viral envelopes to weaken them. Natural killer cells (called “NK cells”) identify any virus-infected cells or tumor cells and destroy them with their cytotoxins.

But sometimes, threats can evade the innate immune system, or may be too persistent or sturdy for these initial defenses to overcome. In these cases, the adaptive immune system gets involved.

The adaptive immune system is more specialized. It can “learn” how to respond to individual threats and has an “immune memory”, remembering how it eliminated and eradicated pathogens or toxins in the past.

Here is how the adaptive immunity and its parts work:

• T lymphocytes activate the adaptive immune T cell responses (T helper cells), detect tumor and virus cells, and destroy them. Once they’ve finished that task, they can either remain T helper cells or turn into memory T cells to facilitate future eliminations of that same threat.
• B lymphocytes are activated by T cells. They’re produced in the bone marrow and can turn into specific immune cells, or make copies of themselves to turn into plasma cells that produce the specialized antibodies required to overwhelm and destroy the pathogens. Once the threat is neutralized, many of the B cells activated turn into memory B cells to remember the best way to destroy that same threat in the future.
• Antibodies recognize germs and pathogens and other threats and attach to them, marking them for destruction while also rendering them harmless. They’re produced by B cells, and are crucial for the body’s response to specific threats. Your lymph nodes grow less effective at registering and eliminating threats.

How the Immune System Changes with Age

The greatest change to your immune system as you age is in your adaptive immune system. While there are some inefficiencies in your innate immunity—weaker skin barriers, less effective production of mucus and tears, etc.—it’s your adaptive response to threats that suffers the most.

As you age, your thymus begins to produce fewer T cells. This means that with every immune reaction, more T cells are being turned into memory T cells to remember the threats, but not enough fresh T cells are being produced to attack new threats as they arise. T cell activation can also happen more slowly over time due to senescent immune cells.

Persistent infections —such as HSV or CMV—can expand specific memory T-cell clones, crowding out naive T cells. Overworked immune systems can lead to senescent T cells, which are unable to proliferate and no longer respond to antigens.

There are other changes, too:

• Phagocyte production decreases, which can often lead to less effective elimination of bacterial invaders.
• Hematopoietic stem cells (HSC) that are needed to produce new leukocytes that turn into specialized immune cells grow less effective at renewing.
• Antibody and B cell production decreases as a result of declining humoral immunity.
• The cytotoxicity (ability to kill off tumor and virus-infected cells) of NK cells decreases.
• The antigen-presenting cells diminish in function, and this impairment can lead to slower recognition and elimination of antigens.

However, the innate immune response is also affected, most notably in your body’s inflammatory response to invaders.

While inflammation is crucial for stopping infections and illness, it can be dangerous and harmful if it persists for too long. It can speed up the breakdown of crucial body cells while slowing repairs to the affected area.

Given the slower immune reaction caused by advancing age, inflammation typically lasts longer and can be detrimental to the health of senior citizens and the elderly.

Key Causes of Immunosenescence

There are a number of factors that can contribute to immunosenescence:

• Increased oxidative stress and damage to the DNA (including telomere shortening), which lead to genetic and epigenetic changes
• Greater prevalence of persistent viral and bacterial infections
• Chronic inflammation resulting from aging related diseases or illnesses
• Changes in the gut microbiome
• Imbalances of proinflammatory cytokines
• Reduced efficacy of vaccinations, a common effect among the elderly
• Reduced thymus function, which shrinks with age
• Impaired T cell function
• Accumulation of senescent cells, which can release inflammatory molecules and contribute to chronic low-grade inflammation
• Long-term exposure to environmental pollutants, toxins, and carcinogens

Decreased immunity is a natural side effect of the aging process, but the factors listed above can drastically speed up your immune decline.

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Impact of Immunosenescence on Health

There are two significant impacts that immunosenescence can have on your health:

• Increased risk of infections and illnesses. If your immune response—particularly your adaptive immune response—is less effective at protecting you, you will be more vulnerable to infections and illnesses. Pathogens may cause more damage or persist for longer before they are eradicated, and you may find yourself growing sick more frequently, possibly even with more severe symptoms.
• Chronic inflammation. Because your body takes longer to eliminate threats, inflammation may last longer, perhaps even remain present persistently, to the point of becoming chronic. This can lead to accelerated immune aging and even slower immune response to pathogens.

If your immune system begins to age, it can trigger a downward spiral that leads to long-term health problems—and may even shorten your lifespan, ultimately.

Signs of an Aging Immune System

How can you tell if your immune system is aging or slowing down?

• Your body responds more slowly to threats, so pathogens and toxins may cause greater damage before they are neutralized or eliminated.
• You are more prone to getting sick, and sickness may last longer.
• Vaccines, flu shots, and medications may not protect you as effectively or for as long as they did when you were younger.
• Healing from wounds and infections takes longer because there are fewer cells to facilitate the healing and repair process.
• Your immune system grows less effective at recognizing threats, including cancer. Elderly patients and seniors have a higher risk of developing cancer for this reason, but it can go undetected for longer because your body isn’t able to see it as a threat as quickly.
• You suffer from more allergies or hypersensitivities.

All of these are your body’s way of telling you that your immune system is struggling and needs your help to reinvigorate your internal defenses!

Lifestyle Factors That Affect Immunosenescence

Below you’ll see the main factors that can impact your immune health as you age.

Dietary and Nutritional Support for Immune Health

The food you eat can lead to either the improvement or deterioration of your immune health. It’s no exaggeration to say that your diet can have a massive impact on your body’s ability to fight infectious disease.

Some foods can impair or overtax your immune system:

• Foods rich in chemical and artificial ingredients
• Inflammatory foods high in refined sugars, refined carbohydrates, and unhealthy fats
• Foods that contain large quantities of processed ingredients and very little nutrition
• Fried and deep fried foods
• Alcohol

These foods are best avoided as much as possible, and should be limited as much as possible, from your diet.

Instead, you should focus on the foods that provide immune support:

• Healthy plant-based unsaturated fats, which have anti-inflammatory properties
• Whole grains, nuts, seeds, and legumes which are rich in protein and fiber
• Antioxidant-rich foods like green tea, red grapes, cocoa, olive oil, and berries that combat inflammaging and prevent oxidative damage
• Foods that contain probiotics and prebiotics, which will improve immune response in your digestive tract
• Fruits and vegetables rich in micronutrients, such as Vitamin A, Vitamin C, Vitamin E, zinc, calcium, and magnesium

Following a diet similar to the Mediterranean Diet or the DASH Diet—both of which prioritize whole, antioxidant-rich, and fiber-rich foods. There are many plant-based foods good for your immunity, and eating in moderation can boost your immune cell function.

Emerging research [1] has also shown that fasting and intermittent fasting (eating for 6-8 hours, fasting for 16-18 hours) can decrease intestinal inflammation, increase gut bacterial activity, and improve immune function.

Exercise and Its Role in Immune Aging

Exercise is one of the best things both younger and older patients can do to prevent immune aging!

Moderate and vigorous cardiovascular exercise can increase the activity of virus-killing cells in your body, both antibodies and white blood cells. It can also improve circulation, which ensures these cells can speed through your bloodstream to reach their destination more quickly.

Strength training also secretes myokines, which have anti-inflammatory properties that can keep your body from over responding to minor threats. Resistance training can be highly effective at balancing your immune system, keeping it active but preventing it from being overactive (which can lead to chronic inflammation and autoimmune disease).

Try to get at least 2-3 cardio workouts per week, along with 2-3 strength training workouts.

Preventive Tips for a Healthier Immune System

To combat aging cellular function and keep your immune system functioning at optimal capacity, try the following:

• Get more Vitamin D. Spend more time in the sun, which will increase your body’s production of Vitamin D naturally. Or if you live in an area with many months of little-to-no sunlight, take Vitamin D supplements to boost your body’s Vitamin D production.
• Wash your hands. Washing your hands before every meal and throughout the day minimizes your exposure to germs and pathogens, reducing the strain on your immune system.

• Maintain healthy weight. Obesity has been linked to reduced immune function and increased chronic inflammation. Maintaining a healthy weight will effectively keep your internal organs and systems running at optimal capacity.
• Prioritize sleep. A lack of sleep can cause diminished resistance to disease, increased susceptibility to infection, and impaired immune function. Aim for a minimum of 7 hours of sleep per night. Prioritize your sleep habits and sleep routines because sleep is proven to affect your immune system.
• Reduce stress. Stress can contribute to weight gain, impact sleep, and impair your immune function. Meditate, practice mindfulness, do Yoga, read, listen to music, do puzzles, and try everything you can to relax and combat stress in your daily life in order to boost your immunity.

• Quit smoking. Smoking drastically elevates your risk of immune system issues (such as rheumatoid arthritis), along with cardiovascular disease and lung cancer. Quit smoking, and your body will be far more effective at fighting off age related diseases and infections.
• Drink less. Moderate alcohol intake. In excess, it can be incredibly harmful and cause long-term damage, including to your immune system, liver, cognition, and more. Stick with 1-2 drinks, 2-3 times a week., And aim for fewer than five drinks per week to maximize your body’s ability to respond to invading threats.
• Get frequent checkups. Medical screenings and frequent doctor visits can help you detect infection or illness early on, and address it before it causes widespread inflammation or suppresses your immune activity.

You don’t need to overhaul your life, but making the few small changes above can lead to massive improvements in your immune health and function!

Wrapping Up

Immune senescence is a very real, very concerning problem that all of us are likely to face as we age. Our bodies will grow less efficient at producing the cells necessary to fight off invaders, inflammation will increase, and the protective mechanisms that keep us healthy will become less effective.

Understanding this is crucial because it allows us to start taking action to combat the immune-reducing effects of age now, (hopefully) years before it becomes a problem. Making the lifestyle changes recommended above will balance your immune system and encourage more effective response to disease and infection.

With a healthy diet, exercise routine, and daily habits to back you up, you’ve got the best chance of staying protected against threats for years to come!

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Frequently Asked Questions

At what age is your immune system strongest?

Children and adolescents have the strongest immune systems. Typically, in the years leading up to and during puberty, immune function is at its peak, and will largely remain highly active during adolescence.

At what age does your body start to decline?

The decline of your immune system will usually begin around age 50, growing more noticeable during your 50s and 60s, and significantly pronounced by the time you reach your 60s and 70s. You’ll find you are more susceptible to disease and infection starting in your 50s.

What is the most common autoimmune disease?

The most common autoimmune disease is thyroid diseases such as Hashimoto’s thyroiditis and Graves’ disease. . Hashimoto’s thyroiditis especially affects women.

Resources

Immunosenescence

Immunosenescence: molecular mechanisms and diseases

Immune Senescence, Immunosenescence and Aging

Immunosenescence: a key player in cancer development

Chapter 11 Immunosenescence

Immunosenescence, aging and successful aging

Immunosenescence and human vaccine immune responses

In brief: The innate and adaptive immune systems

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