What Does The Immune System Do To Foreign Invaders?

The immune system is a whole network of defender cells, organs, and tissues, programmed to keep our bodies healthy. The main task of this network is to serve as a defense against many types of invaders like parasites, fungi, bacteria, and viruses—all with the potential to harm a person’s health. Most immune systems are adaptable, creating specific cells to tackle any potential illnesses and diseases.

What does the immune system do to foreign invaders? Through moderate levels of temperature and nutrients, the human body provides an ideal environment for many disease-causing microbes or pathogens to grow, thrive, and multiply, taking over and wreaking havoc on our systems. The immune system seeks these microbes out, destroys them, and disposes of them. The attack and force are combined with waste removal and keep our systems functioning!

In this blog post, we will try to not make this discussion overly “science-focused” with a ton of inaccessible jargon. However, we do want to talk about and elucidate what goes on in our bodies, especially considering the lasting impact of the current global pandemic. A lot of immune system support relies on nutrition and there are numerous supplements that may help support the immune system that one can take.

* Disclaimer: This blog post contains affiliate links, which means that we receive a small commission if you purchase through these links. However, this commission comes at no additional cost to you.

Immune System as the Body’s Bodyguard

The Innate Immune System and the First Line of Defense


When asking the question ‘What does the immune system do to foreign invaders?’ it helps to understand the different lines of defense in our bodies. The first part of the immune system is made of initial defenses that most humans have when they are born. This system is called the “innate system” or our nonspecific defense. This part of the immune system is not targeted against any specific pathogen and is a physical barrier against potential diseases.

Foreign invaders, or pathogens, are anything potentially harmful to our bodies that comes from the outside and seeks to multiply and take over our body. While a fair number of bacteria are beneficial, some are pathogenic, as well as parasites, viruses, fungi, and any other microorganism or molecule that is not supposed to be there.

The most obvious part of our innate defense systems is our skin! Skin is the largest barrier we have to prevent pathogens from entering the body. Other physical barriers include the mucous membranes located in our noses and mouths. This membrane produces sticky mucus that traps pathogens, other infectious bacteria, and viruses.

Saliva is also a part of the innate defense system because it both physically washes out all of the pathogens that enter through our mouths and uses enzymes to dissolve pathogens. This washing does a good job of reducing the number of bacteria living in our mouths but also has enzymes to disintegrate a good deal of pathogens. These enzymes are also found in our mucus and tears.

Another innate way to dissolve any pathogens is through our stomach. The stomach produces highly acidic gastric juice which is able to kill any potential bacteria that could be found on the foods that we eat. Stomach acid, spit, mucus, and tears all have enzymes that can dissect bacterial cell walls.

The innate system is the body’s first line of defense against any potential pathogens, germs, or disease-causing viruses. As we go further along, you will see that some cells are created to specifically target other kinds of potential illnesses and viral-infections through our body’s ability to adapt. This is the “Second Line of Defense” and is on the cellular level.

If any disease-causing bacteria, pathogens, or the like, manage to enter the body despite the presence of this first line of defense, the second line of defense will now be summoned to wage war against these invaders. The second line of defense includes specialized cells that will remove these pathogens and are a key part of what the immune system does to foreign invaders.

Rapid Response or the Second Line of Defense

Our immune system has a second line of defense in case any pathogens can make it past our skin, nose, and eyes. This line of defense is still non-specific and depends on our lymphatic system’s presence. White blood cells like phagocytes, neutrophils, and leukocytes, which are scouring our immune system for potentially harmful pathogens, defend our bodies from potential pathogen invasions.

Now, it is kind of freaky to think about any germ making its way through our initial protective barriers. This situation takes place whenever we skim our knees, cut our skin, or get urinary tract infections. These are all examples of situations where pathogens have crossed an invisible line into our systems. The first response is to flood the infected area with blood—if you’ve ever seen a cut get red-hot, that’s the initial inflammatory response and an important step.

As we have talked about inflammation in a previous blog post, an inflammatory response is part of our second line of defense against pathogens or injuries.


When a pathogen is encountered by defensive cells, these cells use hormonal signals for an increase in blood flow to an infected area. Blood vessels then expand that infected part of the body allowing for more white blood cells from bone marrow, neighboring organs, and the lymphatic system to protect the tissue.

White blood cells, also known as phagocytes, are part of this second line of innate defense and are important for our overall health. Unless someone has an autoimmune disorder or immunodeficiency, most bodies can produce white blood cells to fight infections. White blood cells are also important indicators for diseases like cancer—doctors test patients’ white blood cell count to diagnose and treat any potential diseases.

The way white blood cells or phagocytes work is that they completely surround bacteria and then break them down. This breakdown of bacteria is known as “phagocytosis.” Using Greek roots, we can understand that phagocytes are a type of cell that “eats” another cell, and phagocytosis is the action of one cell eating another one.

You know how when you have a cold or a fever you can end up having a really runny nose? Well, that function is also part of the immune system response and brings us to the concept of neutrophils. Oftentimes a large percentage of snot consists of neutrophils that have finished their job.

Neutrophils are cells like phagocytes that also perform phagocytosis when taking down bad bacteria and diseases. They are not limited to one part of the body and can move freely across to fight “antigens” (anything that triggers an immune system response). Neutrophils make up to 55-80% of our white blood cells. They neutralize the bacteria, disperse antiseptics, and then self-destruct in the process.

The Adaptive Immune System

Our immune system’s second line of defense is much more complicated than the first, where the physical presence of a barrier moves to break down or prevent any pathogens from entering our system. The second line of defense consists of white blood cells that circulate our bloodstreams, in case they encounter any pathogens. The adaptive immune system, however, is complicated and requires learning to protect the body.

The second part of the immune system is what we commonly refer to as “immunity.” Immunity continuously develops in our bodies as we grow older. Immunity’s role is fighting against specific kinds of pathogens. This information is based on the immune system’s “database” of specific types of threats, collected from experience. Some of this information happens in-utero but some information, our immune system has to “remember” pathogens to defend us.

The adaptive immune system is composed of specialized cells mostly produced in the lymphatic system. This adaptive, or sometimes referred to as acquired, immunity created “immunological memory” to respond to a specific pathogen and prevent it from spreading throughout the body.


Adaptive immune systems differ from innate immune systems in that the adaptive system is highly specific to a particular kind of pathogen or antigen. This immunological memory also creates long-lived protection within a system. The adaptive response destroys invaders as well as any toxins it may find in the system. However, sometimes this system misinterprets harmless foreign molecules as antigens, causing asthma or allergies.

In adaptive immunity, these helpful cells have “pathogen-specific receptors.” To help this understanding, instead of white blood cells, imagine a bunch of puzzle pieces floating in your bloodstream. They are looking for their specific match to attack and protect the body against this matching piece.

Introducing our immune system superheroes! We’ll make a quick and accessible chart here so that you do not have to remember all of their names. Hopefully, it’s helpful. We think it’s a good thing to have lists.

  • Antigens: Antigens are found around pathogens and help the immune system recognize a potential invader. Remember pathogen-specific receptors? This is the other puzzle piece floating around.
  • Antibodies: Cells that directly recognize and clamp on to antigens. This kind of cell is a special protein. It’s kind of like an internal alarm system. They attract other cells to surround and break down the pathogen. They can be a type of protein secreted by the immune system known as immunoglobin.
  • Basophils: produce histamines when responding to an allergen as well as signaling the presence of any infectious germs.
  • Cytokine: A type of peptide and/or protein that is secreted by immune system cells. Like the antibodies and helper T-cells, cytokines communicate messages across the body and let the body know of potential pathogenic issues.
  • Leukocytes: A type of white blood cell that circulates the bloodstream. Found in the blood and lymph tissue. Leukocytes include granulocytes (like neutrophils), monocytes, and lymphocytes. Leukocytes found in the urine can indicate a urinary tract infection.
  • Lymphocytes: Big-time players of the immune system! There are B- and T-Cells. B-Cells are created in the bone marrow and mature there. T-Cells are also created in the bone marrow but mature in the thymus, which is located under the throat and thyroid between our lungs.
  • Lymph nodes: lymph nodes are small glands located all over our body filtering lymph, an important part of our immune system transportation. They can become swollen when there is an infection or tumor.
  • Macrophages: cells that help with discovering antigens, phagocytosis, and the neutralization of pathogens. They release cytokines to “mark” any potentially bad cells.
  • B-Cells: There are two types of B-cells. When activated, B-Cells grow fast and make plasma cells, which creates antibodies that circulate the bloodstream. There are also memory B-cells, that keep data on pathogens to make it easier to create defense in the future.
  • T-Cells: Like B-Cells, there is more than one kind of T-Cell! There are cytotoxic T-Cells which help with disposing of sick body cells. Then there are helper T-cells, which are like a secondary alarm system, talking to other immune cells in the body and lymphatic system.

As you can see, there are a lot of different cells involved in maintaining our complicated bodies. Immunological memory is a very important part of our system, which leads us to the next topic! Vaccines.

How the Immune System Relaxes

Once a certain illness is defeated, lymphocytes will then keep a record of these viruses or bacteria so your body will be able to remember them throughout your lifetime. In turn, when these disease-causing bacteria or viruses manage to penetrate inside your body for the second time it will be much easier for your lymphocytes to defeat them.

An understanding of this pattern of occurrence has led to the birth of vaccines, which contain weakened antigens that may be injected into the body. The human body is an absolute miracle, producing millions of defender cells every day, and can kill germs and prevent them from causing any illness. The immune system functioning is incredibly important for illness prevention.

Vaccines are basically sending “dead” viruses and pathogens into a bloodstream so immunological memory cells can develop antibodies. Viruses are technically not living organisms, so they cannot die, but the process of developing vaccines weakens their strength and lets our bodies develop an immunological memory. Vaccines are incredibly helpful in preventing and ending pandemics because they are so effective in developing our immune systems.

Relaxing is actually very important to our immune systems. The immune system never relaxes! But it needs you to not be so stressed out all the time. When you are constantly stressed out, your body produces a lot of stress hormones, which weaken the immune system.

Being chronically stressed out has a major effect on our cells, immune system, and even our heart. Obviously, every person has a different body, but managing stress is important maintenance when it comes to your current and future health.


Other Effects on the Immune System

Some chronic disorders can have a major effect on our immune system. Type 2 Diabetes, for instance, causes immune system issues due to inflammatory response. When a person has diabetes, inflammation can come from the immune system reacting to high blood glucose levels. The immune system basically malfunctions and inflames the body. This malfunction can happen with other chronic diseases as well.

As we talked about before, allergic reactions can be part of an immune system malfunction. When the antibodies misinterpret something, like, let’s say, dust, as a dangerous pathogen, it sends the immune system to take care of these “foreign invaders.” Asthma is another “misinterpretation,” where antibodies in the lungs recognize chemicals and substances as potential pathogens in the respiratory system.

Another potential immune system malfunction comes in the form of autoimmune diseases like rheumatoid arthritis, lupus, and multiple sclerosis, which are parts of a perhaps “over-stimulated” immune system. This means that immune cells misinterpret regular cells as toxins. What ends up happening is chronic inflammation and immune system cells are constantly attacking the wrong thing.

However, moving on from doom-and-gloom, the immune system, specifically clinical immunotherapy, can also be used to help those with cancer. Bone marrow transplants have been used to fight and cure aggressive blood cancers, where the donor’s non-weakened immune system can fight the cancer cells and tumors.

Following this transplant of bone marrow or organs, a patient has to take a type of medicine in the category of “immunosuppressant” to prevent the already present immune system from attacking the new one. Transplants can be a hazard if the immune system rejects the new organs or tissue, so immunosuppressants allow these “new neighbors” to move in.

Current research has also revealed the relationship between our genetics and immunity, where approximately three-quarters of immune traits are influenced by variations in genomics. This information will guide further research studying rheumatoid arthritis and other inflammation-based diseases. Another important element of this scientific research emphasizes how much environment and diet have on our immune system’s functions.


How Can We Help Our Immune Systems?

Considering all that our immune system does to defend us from foreign invaders, it’s nice to be able to support it as much as possible. If you’re wondering how to boost your immune system, there are many factors to consider. Like we said before, a stressed-out immune system is a sad immune system, so stress management is the first thing we can do to help our cells. Not just emotional stress or anxiety either but helping with cellular stress using antioxidants helps our immune systems a lot as well.

Other things to do to help your immune system include having a healthy diet and eating nutrient-rich foods. A good way to think of a healthy diet is that it provides the body with the building blocks it needs to create a happy and functioning system. As mentioned before, Type 2 diabetes and heart disease can make an immune system not function properly. Science shows that these potential problems might be mitigated with a healthy diet and exercise.

Sometimes, however, diets do not cover our complete nutrient profile. Scientists have shown that while fresh food is loaded with minerals and vitamins, older adults are not getting enough nutrients from their diets. As you get older, you may recognize that even though you are eating a complete and healthy diet, something may be missing. Another perk of getting older! Luckily, there are numerous immunity supplements you can take that have the potential to effectively supplement those nutrients you might be lacking in your diet.

Besides getting enough rest, reducing stress, and getting enough nutrients, there are other ways to potentially support or to use a popular phrase, “boost” our immune systems. While taking care of ourselves is important, this self-care can include washing your hands enough and making sure to clean meat and fruits before you eat. We talked about stomach acids being an innate immune response, but it is important to make sure we do not overdo it.

As to enhance specific cells, there are so many different kinds of microbes and pathogens, and our body is constantly producing immune system cells in order to protect us. Scientists still do not know the answer regarding which cells to boost, but cellular health, antioxidants, and getting rid of toxins may be helpful.


Speaking of toxins, drinking and smoking have also been shown to weaken our immune systems. When we smoke or ingest alcohol, our body then sends the immune system to defend us from the things we are doing to ourselves intentionally and can’t be there to fight a sneaky pathogen. Everything in moderation, right?

This post started with the question, “what does the immune system do to foreign invaders?” The answer we found is, the immune system does a lot! This system sets up multiple blocks to prevent anything bad from getting into our system, from our innate immune system to the adaptive one. It learns how to protect us with time, recognizing pathogens from vaccines, and adapting to other illnesses. Our immune systems grow with us and are lifelong friends.

So, take care of your friend. Take care of yourself!

*Information on this site is provided for informational purposes and is not meant to substitute for the advice provided by your own physician or other medical professional. You should not use the information contained herein for diagnosing or treating a health problem or disease. If you have or suspect that you have a medical problem, contact your health care provider. Information and statements regarding dietary supplements have not been evaluated by the Food and Drug Administration and are not intended to diagnose, treat, cure, or prevent any disease.


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