Immune System

Your immune system is your body’s first-line defense against invaders like germs. It helps protect you from getting sick and promotes healing when you’re unwell or injured. You can strengthen your imm

What is the immune system?

Your immune system is a large network of organs, white blood cells, proteins, and chemicals. These parts all work together to protect you from germs and other invaders. Your immune system also helps your body heal from infections and injuries.

Function

What does the immune system do

Your immune system works hard to keep you healthy. It does this by:

• Keeping invaders (like germs) out of your body.

• Destroying invaders.

• Limiting how much harm the invaders can do if they’re inside your body.

• Healing damage to your body.

• Adapting to new challenges and threats.

Invaders that your immune system protects you against include:

• Bacteria.

• Viruses.

• Fungi that can cause infections.

• Parasites.

• Cancer cells.

How does the immune system work?

When your immune system is working properly, it:

• Tells the difference between cells that are yours and those that don’t belong in your body.

• Activates and mobilizes to kill germs that may harm you.

• Ends an attack once the threat is gone.

• Learns about germs after you’ve had contact with them and develops antibodies against them.

• Sends out antibodies to destroy germs that try to enter your body in the future.

But things don’t always go this smoothly. Sometimes, your immune system doesn’t work properly. For example, it may be too weak to fight off invaders, or it may launch too strong a response.

Weak immune system

Many different conditions can weaken your immune system and make you more susceptible to infection. Conditions at birth are less common than those that develop later in life, like Type 2 diabetes and cancer.

Overactive immune system

At the other end of the spectrum, your immune system may react too strongly to invaders (real or perceived). It may mount an attack when there’s no invader. Or it may keep attacking after getting rid of an invader. An overactive immune system can lead to problems like autoimmune diseases or allergic reactions.

Anatomy

What parts of your body make up the immune system?

Many parts of your body, including immune system organs and cells, work together to keep you healthy. The main components of your immune system are:

• White blood cells. These immune system cells attack and eliminate harmful germs to keep you healthy. There are many types of white blood cells, and each type has a specific mission in your body’s defense system. Each type also has a different way of recognizing a problem, communicating with other cells, and getting their job done.

• Antibodies. These proteins protect you from invaders by binding to them and initiating their destruction.

• Cytokines. These proteins serve as chemical messengers that tell your immune cells where to go and what to do. Different types of cytokines do different specific tasks, like regulating inflammation. Inflammation happens when your immune cells are warding off invaders or healing damage to your tissues.

• Complement system. This is a group of proteins that team up with other cells in your body to defend against invaders and promote healing from an injury or infection.

• Lymph nodes. These small, bean-shaped organs are like colanders you use to drain pasta. They filter waste products from the fluid that drains from your tissues and cells (lymph) while keeping the good components, like nutrients. You have hundreds of lymph nodes throughout your body, and they’re a vital part of your lymphatic system.

• Spleen. This organ stores white blood cells that defend your body from invaders. It also filters your blood, recycling old and damaged cells to make new ones.

• Tonsils and adenoids. Located in your throat and nasal passage, tonsils and adenoids can trap invaders (like bacteria or viruses) as soon as they enter your body.

• Thymus. This small organ helps T-cells (a specific type of white blood cell) mature before they travel elsewhere in your body to protect you.

• Bone marrow. This soft, fatty tissue inside your bones is like a factory for your blood cells. It makes the blood cells your body needs to survive, including white blood cells that support your immune system.

• Skin. Your skin is a protective barrier that helps stop germs from entering your body. It produces oils and releases other protective immune system cells.

• Mucosa. This three-layered membrane lines cavities and organs throughout your body. It secretes mucus that captures invaders, like germs, for your body to then clear out.

Innate immunity vs. acquired immunity

Innate immunity is protection that you’re born with. Your innate immune system is part of your body’s first-line defense. It responds to invaders right away by attacking any organism that shouldn’t be in your body. It doesn’t need prior training to tell the difference between cells that belong in your body and those that don’t.

The white blood cells involved in innate immunity don’t learn to recognize certain invaders. They also have no memory of attacking invaders and don’t offer protection against specific germs (or the infections they cause) in the future.

That’s where acquired immunity comes into play. Acquired immunity, also called adaptive or specific immunity, is the protection your body gains (acquires) over time from exposure to germs. Certain white blood cells called lymphocytes remember specific invaders and can tell when they don’t belong in your body. So, if those invaders try to get in again, the lymphocytes can quickly spring into action and work with other cells to eliminate the threat.

Vaccines support your acquired immunity by training your cells to identify and destroy invaders before they make you sick.

Conditions and Disorders

What disorders and diseases can affect the immune system?

Conditions that can interfere with the normal workings of your immune system include:

• Allergies. An allergy is your body’s reaction to a substance that’s normally harmless. Your immune system overreacts to the presence of that substance, leading to a range of symptoms from mild to severe.

• Autoimmune diseases. These conditions occur when your immune system attacks its healthy cells by mistake. Lupus and rheumatoid arthritis are examples of common autoimmune diseases.

• Primary immunodeficiency diseases. These inherited conditions prevent your immune system from working properly. They make you more vulnerable to infections and certain diseases.

• Infectious diseases. Infectious diseases happen when germs enter your body, replicate, and cause damage. HIV and mononucleosis (mono) are examples of infectious diseases that weaken your immune system and can lead to serious illness.

• Cancer. Certain types of cancer, like leukemia and lymphoma, can weaken your immune system. That’s because cancer cells may grow in your bone marrow or spread there from somewhere else. Cancer cells in your bone marrow interfere with the normal production of blood cells you need to fight infection.

• Sepsis. Sepsis is an extreme immune response to infection. Your immune system starts damaging healthy tissues and organs. This causes potentially life-threatening inflammation throughout your body.

Signs and symptoms of immune system disorders

Signs and symptoms vary depending on the condition and may include:

• Always feeling tired (fatigue).

• Unexplained fever.

• Unexplained weight loss.

• Drenching night sweats.

• Itchy skin.

• Sore, aching muscles.

• Fingers or toes that tingle or are numb.

• Trouble concentrating or paying attention.

• Hair loss.

• Inflammation, rashes, or redness anywhere on your body.

• Swollen lymph nodes in your neck, armpits, or groin.

Common tests that check the health of your immune system

Healthcare providers often use blood tests to check how well your immune system is working. Specific blood tests your provider may order include:

• Antibody test.

• Complete blood count.

• A complement blood test to check levels of specific types of protein in your blood, such as C3 proteins.

What medications can affect my immune system?

Some medications do important work in your body, but in the process, they can weaken your immune system. These include:

• Corticosteroids.

• Immunosuppressants.

• Chemotherapy and other forms of cancer treatment.

If you need any of these treatments, talk to your healthcare provider about how you can support your immune system.

Care

How can I boost my immune system naturally?

No one likes getting sick, and it’s common to wonder how to improve or strengthen your immune system. Because your immune system is complex, there’s no fast and easy answer that works for everyone on how to build it up. That’s why it’s important to talk to a healthcare provider. They can give you individualized advice based on your medical history. They’ll also talk to you about your lifestyle and daily habits to see what changes you can make.

Here are some general tips to keep your immune system running smoothly:

• Fill your plate with healthy foods. Fruits, veggies, lean sources of protein, and whole grains are just some examples of foods that bolster immune function. Talk to your provider about how different ways of eating, like the Mediterranean diet, can help give you the vitamins you need for a healthy immune system.

• Build exercise into your daily routine. Exercise helps many aspects of your health, including your immune function. Your provider can help you get started with an exercise plan that fits your medical needs and lifestyle.

• Keep a weight that’s healthy for you. Researchers have linked a body mass index (BMI) greater than 30 (obesity) to poorer immune function. Ask your provider what your target weight range should be, and work together to reach it.

• Catch enough ZZZs. Not getting enough sleep can prevent your immune system from working as it should.

• Stay up-to-date on vaccines. Vaccines train your body to fight off germs that can make you sick. Talk to your provider about which vaccines you need and when.

• Avoid smoking and all tobacco products. Tobacco use raises your risk for conditions that can harm your immune system, like rheumatoid arthritis. If you use tobacco, talk to your provider about effective ways to quit.

Additional Common Questions

Why is my immune system so weak?

Many different medical conditions, medications, and lifestyle factors can weaken your immune system and prevent it from defending you as well as it should. If you feel like you’re always sick or have symptoms that never go away, make an appointment with a healthcare provider. They’ll determine if you have a weak immune system and what’s causing the issue.

10 Foods That May Weaken Your Immune System

Your diet affects how you feel and how well your body functions.

While a nutrient-dense, well-rounded diet supports your immune system, a diet that’s low in nutrients and high in ultra-processed foods impairs immune function.

10 foods that may weaken your immune system.

1. Added sugar

No doubt limiting how much added sugar you consume promotes your overall health and immune function.

Foods that significantly raise blood sugar, such as those high in added sugars, increase the production of inflammatory proteins like tumor necrosis factor alpha (TNF-α), C-reactive protein (CRP), and interleukin-6 (IL-6), all of which negatively affect immune function.

This is especially pertinent in people with diabetes, as they can have elevated blood sugar levels for longer than people with well-regulated blood sugar levels.

What’s more, having high blood sugar levels may inhibit the response of neutrophils and phagocytes, two types of immune cells that help protect against infection.

Furthermore, it has been shown that high blood sugar levels may harm gut barrier function and drive gut bacteria imbalances, which can alter your immune response and make your body more susceptible to infection.

For example, a 2012 study in 562 older adults found that those who had elevated blood sugar levels also had lower immune responses and higher levels of the inflammatory marker CRP.

Similarly, many other studies have linked high blood sugar levels to an impaired immune response in people with and without diabetes. Additionally, diets high in added sugar may increase the susceptibility to certain autoimmune diseases, including rheumatoid arthritis, in some populations.

Limiting your intake of foods and beverages high in added sugar, including ice cream, cake, candy, and sugary beverages, can improve your overall health and promote healthy immune function.

Summary

Studies have associated high blood sugar levels with impaired immune response. Limiting your intake of sugary foods and beverages can promote better blood sugar management and immune response.

2. Salty foods

Salty foods like chips, frozen dinners, and fast food may impair your body’s immune response, as high salt diets may trigger tissue inflammation and increase the risk of autoimmune diseases.

In a 2016 study, 6 healthy men first consumed 12 grams of salt per day for 50 days. This was followed by around 50 days of consuming 9 grams of salt per day and then consuming 6 grams per day for a similar duration. Lastly, they consumed 12 grams daily for another 30 days.

On the high salt diet containing 12 grams per day, the men had higher levels of white blood cells called monocytes and inflammatory markers IL-23 and IL-6. They also had lower anti-inflammatory protein IL-10, indicating an excessive immune response.

Salt may also inhibit normal immune function, suppress anti-inflammatory response, alter gut bacteria, and promote the generation of immune cells that are implicated in the pathogenesis of autoimmune diseases.

Researchers believe that excessive salt intake may be associated with an increase in autoimmune diseases in Western countries.

Additionally, eating too much salt has been shown to worsen existing autoimmune diseases like ulcerative colitis, Crohn’s disease, rheumatoid arthritis, and lupus.

Therefore, reducing your intake of table salt and high-salt foods may benefit your immune function.

Summary

Studies show that a high salt intake may impair normal immune function, promote inflammation, and increase your susceptibility to autoimmune diseases.

3. Foods high in omega-6 fats

Your body needs both omega-6 and omega-3 fats to function.

Western diets tend to be high in omega-6 fats and low in omega-3s. This imbalance has been associated with increased disease risk and possibly immune dysfunction.

Diets high in omega-6 fats seem to promote the expression of pro-inflammatory proteins that may weaken the immune response, while diets higher in omega-3 fats reduce the production of those proteins and enhance immune function.

What’s more, studies in people with obesity indicate that a high dietary intake of omega-6 fats may lead to immune dysfunction and increase the risk of certain conditions like asthma and allergic rhinitis.

However, the relationship between omega-6 fats and the immune response is complicated, and more human research is needed.

Regardless, researchers recommend that you maintain a healthy balance of omega-6 to omega-3 fats, which is considered to be around 1:1 to 4:1, to promote overall health.

This means eating more foods that are high in omega-3s — like salmon, mackerel, sardines, walnuts, and chia seeds — and fewer foods that are high in omega-6s, such as sunflower, canola oil, corn oil, and soybean oil.

Summary

Eating more omega-3-rich foods and fewer omega-6-rich foods may promote optimal immune function.

4. Fried foods

Fried foods are high in a group of molecules called advanced glycation end products (AGEs). AEGs are formed when sugars react with proteins or fats during high-temperature cooking, such as during frying.

If levels become too high in your body, AGEs can contribute to inflammation and cellular damage.

AGEs are thought to weaken the immune system in several ways, including by promoting inflammation, depleting your body’s antioxidant mechanisms, inducing cellular dysfunction, and negatively affecting gut bacteria. As such, researchers believe that a diet high in AGEs may increase susceptibility to diseases like malaria and increase the risk of medical conditions like metabolic syndrome, certain cancers, and heart disease.

Cutting back on fried foods like French fries, potato chips, fried chicken, pan-fried steak, fried bacon, and fried fish will reduce your intake of AGEs.

Summary

Fried foods aren’t good for overall health and may cause immune dysfunction. Fried foods are high in AGEs and should be limited in any healthy diet.

5. Processed and charred meats

Like fried foods, processed and charred meats are high in AGEs.

For example, a study that analyzed the AGE content of 549 foods found that fried bacon, broiled hot dogs, roasted skin-on chicken thighs, and grilled steak had the highest AGE contents.

Processed meats are also high in saturated fat. Some research suggests that diets high in saturated fats and low in unsaturated fats may contribute to immune system dysfunction.

Plus, diets high in saturated fat may contribute to systemic inflammation and harm immune function.

Additionally, a high intake of processed meats and charred meat has been linked to various diseases, including colon cancer.

Summary

Diets high in processed meat and meats cooked at high temperatures have been linked to increased disease risk and may harm your immune system.

6. Fast food

Fast food has been linked to many negative health outcomes. Eating it too frequently may also take a toll on your immune system.

Diets high in fast food and highly processed foods may drive inflammation, increase gut permeability, and cause bacterial imbalance in the gut, all of which can negatively affect your immune health.

Fast food can also contain the chemicals bis(2-ethylhexyl) phthalate (DEHP) and diisononyl phthalate (DiNP), which are two types of phthalates. Phthalates can leach into fast food, for example, through packaging or plastic gloves worn during food preparation.

Phthalates are known to disrupt your body’s endocrine, or hormone-producing, system. They may also increase the production of inflammatory proteins that can weaken your immune response to pathogens and cause immune dysregulation.

In addition, phthalates may reduce gut bacteria diversity, which can negatively affect your immune system.

Summary

Keep your intake of fast food to a minimum. Eating too much of it is associated with health risks and may harm your immune system.

7. Foods that contain certain additives

Many food items, especially ultra-processed foods, contain additives to improve shelf life, texture, and taste. Some of these may negatively affect your immune response.

For example, some emulsifiers, which are added to processed foods to improve texture and shelf life, can alter gut bacteria, harm your gut lining, and induce inflammation, all of which can cause immune dysfunction.

Carboxymethylcellulose (CMC) and polysorbate-80 (P80) are commonly used emulsifiers that have been linked to immune dysfunction in rodent studies.

Similarly, human and animal studies have shown that the common additive carrageenan may induce intestinal inflammation and inhibit immune response, although more research is needed to better understand these effects.

Lastly, corn syrup, salt, artificial sweeteners, and the natural food additive citrate may also negatively affect your immune system.

Summary

Ultra-processed foods contain additives like emulsifiers, thickeners, and sweeteners that may affect immune function.

8. Highly refined carbs

Eating highly refined carbs like white bread and sugary baked goods too often may harm your immune system.

These are types of high glycemic foods that cause a spike in your blood sugar and insulin levels, potentially leading to the increased production of free radicals and inflammatory proteins like CRP.

Plus, a diet rich in refined carbs may alter gut bacteria, which can negatively affect your immune system.

Choosing nutritious, high fiber carb sources like starchy vegetables, oats, fruit, and legumes over refined carbs is smart to support immune health.

Summary

A diet high in refined carbs may adversely affect your immune system. Choosing more nutritious carb sources like fruits and starchy vegetables is a better choice for your overall health.

9. Certain high-fat foods

A diet high in saturated fats and low in unsaturated fats has been associated with immune dysfunction.

High saturated fat intake can activate certain signaling pathways that induce inflammation, thus inhibiting immune function. High-fat diets may also increase your susceptibility to infection by suppressing your immune system and white blood cell function.

Additionally, rodent studies have suggested that high-fat diets can cause gut bacteria changes and damage the intestinal lining, potentially increasing infection and disease risk.

Researchers are still investigating how different fatty acids affect the immune system, and more human studies are needed.

That said, eating a well-balanced diet high in fiber and healthy fat sources is likely a good way to support immune health.

Summary

Eating a diet high in saturated fat may impair immune function. Following a balanced, high fiber diet is likely a good way to support immune health.

10. Artificially sweetened foods and beverages

Certain artificial sweeteners have been linked to altered gut bacteria composition, increased inflammation in the gut, and blunted immune response.

Increasing evidence suggests that artificial sweeteners, including sucralose and saccharin, may induce gut bacterial imbalances. Some researchers postulate that overusing artificial sweeteners may be detrimental to immune health. (

Furthermore, some research in rodents and limited case studies in humans also suggest that a high intake of artificial sweeteners may contribute to the progression of autoimmune diseases. However, more research is needed.

That said, not all studies agree, and some have shown that moderate daily intake of those sweeteners does not cause changes in gut bacteria or immune function (62, 63).

Summary

Artificial sweeteners have been associated with alterations in gut bacteria that may harm immune function. Additionally, some research suggests that high intake may contribute to the progression of autoimmune diseases.

The bottom line

You can support your immune system by living a healthy lifestyle.

This means limiting foods and beverages that are high in added sugars and salt, processed meats, and fried foods, all of which may have adverse effects on your body’s immune function.

To support your immune system, it’s best to follow a balanced diet rich in whole, nutrient-dense foods and limit your intake of ultra-processed foods as much as possible.