Gut Health

None of these things are able to get in when your immune system is working, but the moment your immune system stops the door is wide open. Once you die it only takes a few weeks for these organisms to completely dismantle your body and carry it away, until all that’s left is a skeleton. Obviously, your immune system is doing something amazing to keep all of that dismantling from happening when you are alive.

The immune system is complex, intricate and interesting. And there are at least two good reasons for you to know more about it. First, it is just plain fascinating to understand where things like fevers, hives, inflammation, etc., come from when they happen inside your own body. You also hear a lot about the immune system in the news as new parts of it are understood and new drugs come on the market — knowing about the immune system makes these news stories understandable. In this article, we will take a look at how your immune system works so that you can understand what it is doing for you each day, as well as what it is not.

Seeing Your Immune System

• When you get a cut, all sorts of bacteria and viruses enter your body through the break in the skin. When you get a splinter you also have the sliver of wood as a foreign object inside your body. Your immune system responds and eliminates the invaders while the skin heals itself and seals the puncture. In rare cases the immune system misses something and the cut gets infected. It gets inflamed and will often fill with pus. Inflammation and pus are both side-effects of the immune system doing its job.
• When a mosquito bites you, you get a red, itchy bump. That too is a visible sign of your immune system at work.
• Each day you inhale thousands of germs (bacteria and viruses) that are floating in the air. Your immune system deals with all of them without a problem. Occasionally a germ gets past the immune system and you catch a cold, get the flu or worse. A cold or flu is a visible sign that your immune system failed to stop the germ. The fact that you get over the cold or flu is a visible sign that your immune system was able to eliminate the invader after learning about it. If your immune system did nothing, you would never get over a cold or anything else.
• Each day you also eat hundreds of germs, and again most of these die in the saliva or the acid of the stomach. Occasionally, however, one gets through and causes food poisoning. There is normally a very visible effect of this breach of the immune system: vomiting and diarrhea are two of the most common symptoms.
• There are also all kinds of human ailments that are caused by the immune system working in unexpected or incorrect ways that cause problems. For example, some people have allergies. Allergies are really just the immune system overreacting to certain stimuli that other people don’t react to at all. Some people have diabetes, which is caused by the immune system inappropriately attacking cells in the pancreas and destroying them. Some people have rheumatoid arthritis, which is caused by the immune system acting inappropriately in the joints. In many different diseases, the cause is actually an immune system error.
• Finally, we sometimes see the immune system because it prevents us from doing things that would be otherwise beneficial. For example, organ transplants are much harder than they should be because the immune system often rejects the transplanted organ.

Basics of the Immune System

Let’s start at the beginning. What does it mean when someone says “I feel sick today?” What is a disease? By understanding the different kinds of diseases, it is possible to see what types of disease the immune system helps you handle.

When you “get sick”, your body is not able to work properly or at its full potential. There are many different ways for you to get sick — here are some of them:

• Mechanical damage – If you break a bone or tear a ligament you will be “sick” (your body will not be able to perform at its full potential). The cause of the problem is something that is easy to understand and visible.
• Vitamin or mineral deficiency – If you do not get enough vitamin D your body is not able to metabolize calcium properly and you get a disease known as rickets. People with rickets have weak bones (they break easily) and deformities because the bones do not grow properly. If you do not get enough vitamin C you get scurvy, which causes swollen and bleeding gums, swollen joints and bruising. If you do not get enough iron you get anemia, and so on.
• Organ degradation – In some cases an organ is damaged or weakened. For example, one form of “heart disease” is caused by obstructions in the blood vessels leading to the heart muscle, so that the heart does not get enough blood. One form of “liver disease”, known as Cirrhosis, is caused by damage to liver cells (drinking too much alcohol is one cause).
• Genetic disease – A genetic disease is caused by a coding error in the DNA. The coding error causes too much or too little of certain proteins to be made, and that causes problems at the cellular level. For example, albinism is caused by a lack of an enzyme called tyrosinase. That missing enzyme means that the body cannot manufacture melanin, the natural pigment that causes hair color, eye color and tanning. Because of the lack of melanin, people with this genetic problem are extremely sensitive to the UV rays in sunlight.
• Cancer – Occasionally a cell will change in a way that causes it to reproduce uncontrollably. For example, when cells in the skin called melanocytes are damaged by ultraviolet radiation in sunlight they change in a characteristic way into a cancerous form of cell. The visible cancer that appears as a tumor on the skin is called melanoma

Viral or Bacterial Infection

When a virus or bacteria (also known generically as a germ) invades your body and reproduces, it normally causes problems. Generally, the germ’s presence produces some side effect that makes you sick. For example, the strep throat bacteria (Streptococcus) releases a toxin that causes inflammation in your throat. The polio virus releases toxins that destroy nerve cells (often leading to paralysis). Some bacteria are benign or beneficial (for example, we all have millions of bacteria in our intestines and they help digest food), but many are harmful once they get into the body or the bloodstream.

Viral and bacterial infections are by far the most common causes of illness for most people. They cause things like colds, influenza, measles, mumps, malaria, AIDS and so on.

The job of your immune system is to protect your body from these infections. The immune system protects you in three different ways:

1. It creates a barrier that prevents bacteria and viruses from entering your body.
2. If a bacteria or virus does get into the body, the immune system tries to detect and eliminate it before it can make itself at home and reproduce.
3. If the virus or bacteria is able to reproduce and start causing problems, your immune system is in charge of eliminating it.

The immune system also has several other important jobs. For example, your immune system can detect cancer in early stages and eliminate it in many cases.

Bacteria and Viruses

Your body is a multi-cellular organism made up of perhaps 100 trillion cells. The cells in your body are fairly complicated machines. Each one has a nucleus, energy production equipment, etc. Bacteria are single-celled organisms that are much simpler. For example, they have no nucleus. They are perhaps 1/100th the size of a human cell and might measure 1 micrometer long. Bacteria are completely independent organisms able to eat and reproduce – they are sort of like fish swimming in the ocean of your body. Under the right conditions bacteria reproduce very quickly: One bacteria divides into two separate bacteria perhaps once every 20 or 30 minutes. At that rate, one bacteria can become millions in just a few hours.

A virus is a different breed altogether. A virus is not really alive. A virus particle is nothing but a fragment of DNA in a protective coat. The virus comes in contact with a cell, attaches itself to the cell wall and injects its DNA (and perhaps a few enzymes) into the cell. The DNA uses the machinery inside the living cell to reproduce new virus particles. Eventually the hijacked cell dies and bursts, freeing the new virus particles; or the viral particles may bud off of the cell so it remains alive. In either case, the cell is a factory for the virus.

Components of the Immune System

One of the funny things about the immune system is that it has been working inside your body your entire life but you probably know almost nothing about it. For example, you are probably aware that inside your chest you have an organ called a “heart”. Who doesn’t know that they have a heart? You have probably also heard about the fact that you have lungs and a liver and kidneys. But have you even heard about your thymus? There’s a good chance you don’t even know that you have a thymus, yet its there in your chest right next to your heart. There are many other parts of the immune system that are just as obscure, so let’s start by learning about all of the parts.

The most obvious part of the immune system is what you can see.

For example, skin is an important part of the immune system. It acts as a primary boundary between germs and your body. Part of your skin’s job is to act as a barrier in much the same way we use plastic wrap to protect food. Skin is tough and generally impermeable to bacteria and viruses. The epidermis contains special cells called Langerhans cells (mixed in with the melanocytes in the basal layer) that are an important early-warning component in the immune system. The skin also secretes antibacterial substances. These substances explain why you don’t wake up in the morning with a layer of mold growing on your skin — most bacteria and spores that land on the skin die quickly.

Your nose, mouth and eyes are also obvious entry points for germs. Tears and mucus contain an enzyme (lysozyme) that breaks down the cell wall of many bacteria. Saliva is also anti-bacterial. Since the nasal passage and lungs are coated in mucus, many germs not killed immediately are trapped in the mucus and soon swallowed. Mast cells also line the nasal passages, throat, lungs and skin. Any bacteria or virus that wants to gain entry to your body must first make it past these defenses.

Once inside the body, a germ deals with the immune system at a different level. The major components of the immune system are:

• Thymus
• Spleen
• Lymph system
• Bone marrow
• White blood cells
• Antibodies
• Complement system
• Hormones

Let’s look at each of these components in detail.

Lymph System

The lymph system is most familiar to people because doctors and mothers often check for “swollen lymph nodes” in the neck. It turns out that the lymph nodes are just one part of a system that extends throughout your body in much the same way your blood vessels do. The main difference between the blood flowing in the circulatory system and the lymph flowing in the lymph system is that blood is pressurized by the heart, while the lymph system is passive. There is no “lymph pump” like there is a “blood pump” (the heart). Instead, fluids ooze into the lymph system and get pushed by normal body and muscle motion to the lymph nodes. This is very much like the water and sewer systems in a community. Water is actively pressurized, while sewage is passive and flows by gravity.

Lymph is a clearish liquid that bathes the cells with water and nutrients. Lymph is blood plasma — the liquid that makes up blood minus the red and white cells. Think about it — each cell does not have its own private blood vessel feeding it, yet it has to get food, water, and oxygen to survive. Blood transfers these materials to the lymph through the capillary walls, and lymph carries it to the cells. The cells also produce proteins and waste products and the lymph absorbs these products and carries them away. Any random bacteria that enter the body also find their way into this inter-cell fluid. One job of the lymph system is to drain and filter these fluids to detect and remove the bacteria. Small lymph vessels collect the liquid and move it toward larger vessels so that the fluid finally arrives at the lymph nodes for processing.

Lymph nodes contain filtering tissue and a large number of lymph cells. When fighting certain bacterial infections, the lymph nodes swell with bacteria and the cells fighting the bacteria, to the point where you can actually feel them. Swollen lymph nodes are therefore a good indication that you have an infection of some sort.

Once lymph has been filtered through the lymph nodes it re-enters the bloodstream.

Thymus

The thymus lives in your chest, between your breast bone and your heart. It is responsible for producing T-cells (see the next section), and is especially important in newborn babies – without a thymus a baby’s immune system collapses and the baby will die. The thymus seems to be much less important in adults – for example, you can remove it and an adult will live because other parts of the immune system can handle the load. However, the thymus is important, especially to T cell maturation (as we will see in the section on white blood cells below).

Spleen

The spleen filters the blood looking for foreign cells (the spleen is also looking for old red blood cells in need of replacement). A person missing their spleen gets sick much more often than someone with a spleen.

Bone marrow

Bone marrow produces new blood cells, both red and white. In the case of red blood cells the cells are fully formed in the marrow and then enter the bloodstream. In the case of some white blood cells, the cells mature elsewhere. The marrow produces all blood cells from stem cells. They are called “stem cells” because they can branch off and become many different types of cells – they are precursors to different cell types. Stem cells change into actual, specific types of white blood cells.

White blood cells

White blood cells are described in detail on the next page.

Antibodies

Antibodies (also referred to as immunoglobulins and gammaglobulins) are produced by white blood cells. They are Y-shaped proteins that each respond to a specific antigen (bacteria, virus or toxin). Each antibody has a special section (at the tips of the two branches of the Y) that is sensitive to a specific antigen and binds to it in some way. When an antibody binds to a toxin it is called an antitoxin (if the toxin comes from some form of venom, it is called an antivenin). The binding generally disables the chemical action of the toxin. When an antibody binds to the outer coat of a virus particle or the cell wall of a bacterium it can stop their movement through cell walls. Or a large number of antibodies can bind to an invader and signal to the complement system that the invader needs to be removed.

Antibodies come in five classes:

• Immunoglobulin A (IgA)
• Immunoglobulin D (IgD)
• Immunoglobulin E (IgE)
• Immunoglobulin G (IgG)
• Immunoglobulin M (IgM)

Whenever you see an abbreviation like IgE in a medical document, you now know that what they are talking about is an antibody.

Complement System

The complement system, like antibodies, is a series of proteins. There are millions of different antibodies in your blood stream, each sensitive to a specific antigen. There are only a handful of proteins in the complement system, and they are floating freely in your blood. Complements are manufactured in the liver. The complement proteins are activated by and work with (complement) the antibodies, hence the name. They cause lysing (bursting) of cells and signal to phagocytes that a cell needs to be removed.

Hormones

There are several hormones generated by components of the immune system. These hormones are known generally as lymphokines. It is also known that certain hormones in the body suppress the immune system. Steroids and corticosteroids (components of adrenaline) suppress the immune system.

Tymosin (thought to be produced by the thymus) is a hormone that encourages lymphocyte production (a lymphocyte is a form of white blood cell – see below). Interleukins are another type of hormone generated by white blood cells. For example, Interleukin-1 is produced by macrophages after they eat a foreign cell. IL-1 has an interesting side-effect – when it reaches the hypothalamus it produces fever and fatigue. The raised temperature of a fever is known to kill some bacteria.

Tumor Necrosis Factor

Tumor Necrosis Factor (TNF) is also produced by macrophages. It is able to kill tumor cells, and it also promotes the creation of new blood vessels so it is important to healing.

Interferon

Interferon interferes with viruses (hence the name) and is produced by most cells in the body. Interferons, like antibodies and complements, are proteins, and their job is to let cells signal to one another. When a cell detects interferon from other cells, it produces proteins that help prevent viral replication in the cell.

Immune System Mistakes

Sometimes the immune system makes a mistake. One type of mistake is called autoimmunity: the immune system for some reason attacks your own body in the same way it would normally attack a germ.

Two common diseases are caused by immune system mistakes. Juvenile-onset diabetes is caused by the immune system attacking and eliminating the cells in the pancreas that produce insulin. Rheumatoid arthritis is caused by the immune system attacking tissues inside the joints.

Allergies are another form of immune system error. For some reason, in people with allergies, the immune system strongly reacts to an allergen that should be ignored. The allergen might be a certain food, or a certain type of pollen, or a certain type of animal fur. For example, a person allergic to a certain pollen will get a runny nose, watery eyes, sneezing, etc. This reaction is caused primarily by mast cells in the nasal passages. In reaction to the pollen the mast cells release histamine. Histamine has the effect of causing inflammation, which allows fluid to flow from blood vessels. Histamine also causes itching. To eliminate these symptoms the drug of choice is, of course, an antihistamine.

The last example of an immune system mistake is the effect the immune system has on transplanted tissue. This really isn’t a mistake, but it makes organ and tissue transplants nearly impossible. When the foreign tissue is placed inside your body, its cells do not contain the correct identification. Your immune system therefore attacks the tissue. The problem cannot be prevented, but can be diminished by carefully matching the tissue donor with the recipient and by using immunosuppressing drugs to try to prevent an immune system reaction. Of course, by suppressing the immune system these drugs open the patient to opportunistic infections.

Foods that boost Immunity

• Carotenoids. Beta carotene increases the number of infection-fighting cells, natural killer cells, and helper T-cells, as well as being a powerful antioxidant that mops up excess free radicals that accelerate aging. Like the other “big three” antioxidants, vitamins C and E, it reduces the risk of cardiovascular disease by interfering with how the fats and cholesterol in the bloodstream oxidize to form arterial plaques. Studies have shown that beta carotene can lower the risk of cardiovascular disease, especially strokes and heart attacks, giving scientific credence to the belief that a carrot a day can keep the heart surgeon away. Beta carotene also protects against cancer by stimulating the immune cells called macrophages to produce tumor necrosis factor, which kills cancer cells. It has also been shown that beta carotene supplements can increase the production of T-cell lymphocytes and natural killer cells and can enhance the ability of the natural killer cells to attack cancer cells

Beta carotene is the most familiar carotenoid, but it is only one member of a large family. Researchers believe that it is not just beta carotene that produces all these good effects, but all the carotenoids working together. This is why getting carotenoids in food may be more cancer-protective than taking beta carotene supplements.

The body converts beta carotene to vitamin A, which itself has anticancer properties and immune-boosting functions. But too much vitamin A can be toxic to the body, so it’s better to get extra beta carotene from foods and let the body naturally regulate how much of this precursor is converted to the immune-fighting vitamin A. It’s highly unlikely that a person could take in enough beta carotene to produce a toxic amount of vitamin A, because when the body has enough vitamin A, it stops making it.

• Bioflavenoids. A group of phytonutrients called bioflavenoids aids the immune system by protecting the cells of the body against environmental pollutants. Bioflavenoids protect the cell membranes against the pollutants trying to attach to them. Along the membrane of each cell there are microscopic parking spaces, called receptor sites. Pollutants, toxins, or germs can park here and gradually eat their way into the membrane of the cell, but when bioflavenoids fill up these parking spots there is no room for toxins to park. Bioflavenoids also reduce the cholesterol’s ability to form plaques in arteries and lessen the formation of microscopic clots inside arteries, which can lead to heart attack and stroke. Studies have shown that people who eat the most bioflavenoids have less cardiovascular disease.A diet that contains a wide variety of fruits and vegetables, at least six servings per day, will help you get the bioflavenoids needed to help your immune system work in top form
• Zinc. This valuable mineral increases the production of white blood cells that fight infection and helps them fight more aggressively. It also increases killer cells that fight against cancer and helps white cells release more antibodies. Zinc supplements have been shown to slow the growth of cancer.

Zinc increases the number of infection-fighting T-cells, especially in elderly people who are often deficient in zinc, and whose immune system often weakens with age. The anti-infection hype around zinc is controversial. While some studies claim that zinc supplements in the form of lozenges can lower the incidence and severity of infections, other studies have failed to show this correlation. A word of caution: too much zinc in the form of supplements (more than 75 milligrams a day) can inhibit immune function. It’s safest to stick to getting zinc from your diet and aim for 15 to 25 milligrams a day.

For infants and children, there is some evidence that dietary zinc supplements may reduce the incidence of acute respiratory infections, but this is controversial. The best source of zinc for infants and young children is zinc-fortified cereals.

• Garlic. This flavorful member of the onion family is a powerful immune booster that stimulates the multiplication of infection-fighting white cells, boosts natural killer cell activity, and increases the efficiency of antibody production. The immune-boosting properties of garlic seem to be due to its sulfur-containing compounds, such as allicin and sulfides. Garlic can also act as an antioxidant that reduces the build-up of free radicals in the bloodstream. Garlic may protect against cancer, though the evidence is controversial. Cultures with a garlic-rich diet have a lower incidence of intestinal cancer. Garlic may also play a part in getting rid of potential carcinogens and other toxic substances. It is also a heart-friendly food since it keeps platelets from sticking together and clogging tiny blood vessels.
• Selenium. This mineral increases natural killer cells and mobilizes cancer-fighting cells. Best food sources of selenium are whole grains, vegetables (depending on the selenium content of the soil they’re grown in), brown rice, egg yolks, sunflower seeds, garlic, and Brazil nuts.
•  Omega-3 fatty acids. A study found that children taking a half teaspoon of flax oil a day experienced fewer and less severe respiratory infections and fewer days of being absent from school. The omega 3 fatty acids in flax oil and fatty fish (such as salmon, tuna, and mackerel) act as immune boosters by increasing the activity of phagocytes, the white blood cells that eat up bacteria. (Perhaps this is why grandmothers used to insist on a daily dose of unpalatable cod liver oil.) Essential fatty acids also protect the body against damage from over-reactions to infection. When taking essential fatty acid supplements, such as flax or fish oils, take additional vitamin E, which acts together with essential fatty acids to boost the immune system. One way to get more omega-3 fatty acids in your diet is to add one to three teaspoons of flax oil to a fruit smoothie.

Reference:

Marshall Brain “How Your Immune System Works” 1 April 2000.
HowStuffWorks.com: 10 January 2017