August 2005

Manitoba Women’s Institute Educational Program

The Immune System

Written by Ann McConkey, R.D.
Women’s Health Clinic
419 Graham Avenue
Winnipeg, Manitoba R3C 0M3
Ph: (204) 947-1517

What is the Immune System?

The immune system is a remarkably complex, vast and sophisticated network of organs, tissues, cells and chemicals that work together to recognize, identify and rid the body of germs. It can be compared to a defending army which is always prepared to protect the body from invaders. This elaborate defense system has the ability to recognize millions of different germs and can produce substances or weapons to match up with and wipe out each one of them. It is a constantly vigilant system of which we are basically unaware.

The immune system has no central location or spot but is located in various places in the body. The main organs of the immune system are the bone marrow, thymus gland, spleen, and lymph nodes.

All cells of the immune system begin their development from primitive stem cells in the bone marrow, which is the soft tissue in the hollow center of the bones. Then they leave the bone marrow and find their way to the thymus (an organ that lies under the breastbone) where they mature. White cells are carried throughout the body by the lymph system and bloodstream. The lymph channels are a microscopic networks of channels that carry lymph. Lymph is a clear fluid that bathes the tissues of the body. When germs get into the lymph system this special fluid acts as a cleanser by surrounding the germs and drawing them into the lymphnodes and spleen, there the lymphocytes kill the germs. The lymph nodes are small clusters of glandular tissue, which are located along the lymph channels mainly in the groin, abdomen, armpits, and neck.

Who are the Invaders?

The germs or invaders, which the immune system fends off are bacteria, fungi, protozoa, and viruses.

Bacteria:	some are friendly and live in our intestines but some can do damage. They multiply and give off toxins (poisons). Examples of harmful bacteria are the ones called salmonella, gonorrhea, and streptococcus.
Fungi:	can be mushrooms, yeast, and molds. Most plant diseases are caused by fungi. Most fungi do not cause any problems for people. One that does is candid albicans. It can live in the mouth causing thrush or in the vagina where we call it a "yeast infection".
Protozoa:	are parasites. Many live in the intestines of healthy people. Only some cause diseases such as the ones that cause malaria and tooplasmosis (the one a pregnant woman can get from cats).
Viruses:	are the smallest organisms know to science. For a size comparison, if a bacteria was the size of a car, a virus would be the size of a tire. Viruses aren’t whole cells, they are genes inside a protein coat. In order to multiply, a virus enters a cell, inserts its genes into the cell’s genes, and tells it to make more viruses. The cell then stops doing what it normally does and starts making viruses. These new viruses then push out of cell and go on to infect other cells. Some viruses can even take part of the host cell’s outer coat from the host cell which helps them hide from the immune system.

How Does the Immune System Identify Invaders?

For the immune system to be able to identify invaders, it has to be able to tell the difference between what belongs to the body and what doesn’t. Every part of our body has on it a particular marker, like a fingerprint, which our immune system identifies as "self". This maker is known as our HLA type – human leucocyte antigen. All other substances do not have this particular maker and so are identified as "foreign", and thus need to be attacked and destroyed. This is why organ transplants can be rejected, as they are "foreign". So, people receiving transplants need to take drugs, which suppress the immune system in order to be able to keep the transplanted organ. The foreign substance that causes activation of the immune system is called antigens. An antigen can be bacteria, virus, or other foreign substance.

What Can Go Wrong?

How the Immune System Works

Let us follow a cold virus to see just how the immune system functions. The cold virus has made its way past the first line of defense - the skin, hairs in the nostrils, cilia (hairs) in the lungs, mucous membranes of the mouth, throat and lungs, tears in the eyes and saliva in the mouth.

If the virus gets past these defenses, it will attack the lining of the respiratory tract. The virus multiples in the respiratory tract cells and from there spreads to other parts of the body via the blood stream and lymphatic system. The infected cells produce a substance called interferon which alerts healthy cells in the vicinity that there is a virus in their midst and helps protect these cells from viral infection.

Meanwhile the body’s army of white cells is on constant patrol. The first white cells to arrive at the site are the macrophages. They will attack any cell that does not have the body’s special marker or fingerprint. First, the macrophages tag the invader so that the T-cells (a type of lymphocyte) can identify it. After tagging it, they release chemicals that attract more white cells to the site. Then, they surround the virus and eat it up. The macrophages also secrete a hormone called interleukin 1, which causes a fever. A fever is an inhospitable environment for germs so is part of the body’s defense mechanism.

Now the lymphocytes come into action - they are the most important part of the immune system. There are three types of lymphocytes - T-cells, B-cells, and natural killer cells. These are also subsets of T and B-cells. The first lymphocyte onto the scene is the T-helper cells (also called T4-cells). The T-helpers are like the conductors of a symphony. They send chemical signals to other T and B-cells to send them into action and orchestrate an organized attack on the virus. T-killer cells in response to a message from T-helpers migrate from the lymph tissue to the site of the invasion where they attach onto cells infected with the virus. T-killers then secret a chemical that kills the virus before it has a chance to multiply.

T-helper also sends a message to activate the B-cells to help defend the body from invaders. B-cells rest inactive in the lymph system until called into action is T-helpers. When B-cells receive the signal they start to divide into two types of cells. One type is the B-plasma cell, which produce antibodies. Antibodies are special proteins called immunoglobulins or gammaglobulins (e.g. IgM. IgG, IgA, IgD and IgE). Antibodies are very specific and will match the antigen on only one specific germ, similar to a lock and key. Each antibody is like a lock which fits onto the antigen (germ) key.

Antibodies help eliminate germ in many ways. They clump germs together so they are easier to remove, they can kill germs directly, they can coat and neutralize poisonous substances (toxins) or they can attract other white cells to the scene. Within a few weeks of being exposed to a virus, antibodies specific to that virus begin to circulate in your blood and lymph system. They stay in your body for many years to help against future infection by that same kind of virus. They could be likened to spies who learn to recognize a particular foreign substance and remain on the lookout for this invader.

The other B-cells become B-memory cells (there are also T-memory cells). The first time a virus enters your body it can take up to a week for your immune system to start to destroy it. If the same virus appears again in the future, the B-memory cells will remember it, enabling the body to produce a much faster and more vigorous immune attack than the first time.

Another kind of lymphocyte are the natural killer cells. They recognize invaders and act independently. They kill germs through direct contact by producing a poison called a cytotoxin.

When the infection is under control, the T-helpers trigger T-suppressor cells. Suppressors tell B-cells and T-cells to slow and stop what they are doing so the immune system can return to its normal state.

Another kind of white cells are the granulocytes which include neutrophils, basophils, and esinopils. These are the most common immune cells in your body. These are the cells that cause redness and swelling when you have a cut, scrape or infection. They are the main constituents of pus. When there is an infection their numbers increase rapidly which is referred to as a "high white count".

How Can I Boost My System?

What we eat is very important. There is a myriad of nutrients, over 50 in total that we know of, that are needed for good health. We need the macro-nutrients-carbohydrates for fuel and energy, protein for tissue building, maintenance and repair, and fat for carrying the fat-soluble vitamins A, D, E, and K, and as a constituent of all hormones and cells. We also need the micro-nutrients, which are all of the vitamins and minerals. These play complex roles in all the chemical pathways in our bodies, helping our bodies function well, maintaining the delicate balance of our bodies and maintaining our immune systems.

There are also substances such as phytoestrogens, antioxidants, cancer-fighting nutrients, fiber and many others which we are just beginning to completely understand. Many of these are particularly important for reducing our risk of disease such as cancer, heart disease, and stroke. We know, for example, that people who eat at least 5 servings of fruits and vegetables each day have a lower incidence of cancer and heart disease. Some nutrients are particularly important for strengthening the immune system. These are protein, minerals such as iron, copper, magnesium, selenium, zinc and vitamins such as A, C, E, and certain B vitamins, B6 (pyridoxine), B12 and folic acids. Essential fatty acids (constituents of fats) are also important. (See Appendix A for a list of foods which contain these nutrients.)

How Can I Possibly Obtain All These Nutrients?

You can get all the nutrients you need by following a well-balanced health eating plan such as one promoted by Canada’s Food guide to Healthy Eating. If this looks too daunting, just pick one or two small goals to start with, and work up slowly from there. (For example, I’ll buy 100% whole wheat bread on my next shopping trip", or "I’ll try to eat one vegetable and one fruit each day ".) Obtaining as much variety as possible is particularly important. The more variety you have, the more likely you are to meet all of your nutrient needs. Variety means different types of grains (preferably whole grains) - such as wheat, rye, rice, oats, corn, buckwheat, millet, barley, etc. different vegetables and fruits and different types of protein foods, both animal proteins such as meat, fish, poultry and eggs and plant proteins, pulses (chickpeas, lentils, soy beans, etc), nuts, seeds and tofu.

One item, which is easy to add and really gives a nutrition boost, is wheat germ. Add wheat germ to any baked goods (substitute for part of the flour or just add extra to a prepackaged mix) hot or cold cereal, casseroles, meatloaf, hamburgers, blender drink, chili, soup, spaghetti sauce, etc.

Should I take a Supplement?

A multivitamin/mineral preparation supplies about 20 – 25 nutrients, less than half of what we require. If you feel more comfortable taking one, it will not hurt and it might help. Older adults in particular seem to benefit from a daily supplement. However, you do need to eat well to be truly healthy. So if you choose relatively healthy foods most times you eat, you will be eating well. If you do obtain all the needed nutrients you will have more vitality and will be healthier – both in the short run (fewer colds and flus) and in the long run (reduced risk of osteoporosis, cancer, and heart disease). So eat well to help you feed your body, mind, and soul. And, most of all enjoy! Food should be fun and taste great, and healthy food can be just that.

Herbs

Some people take herbs to strengthen the immune system, however much more research needs to be done to determine the effectiveness of these herbs. Some herbs which may help are aloe, astragalus (or Huang Qi), cat’s claw, Echinacea, garlic, gingko (or gingko biloba), ginseng, goldenseal, licorice root, acidophilus, bioflavonoid and coenzyme Q10.

Other Factors

While we know much about how the immune system works, there are many other factors involved that we do not yet fully understand.

One is the placebo response. A placebo is and inactive pill ("sugar pill") often given to people as part of a research study. The participants do not know if they have been given the medicine or a placebo, yet many people given a placebo will heal. Does this mean that if a person believes they have been given a medicine, that they can somehow mobilize their own immune system into action? This is quite a hopeful thought.

Another interesting phenomenon is how people respond differently to the same germ. Many times a virus, for example, will infect some people in a home or workplace, while other people emerge unscathed. What makes the difference? Is it genetics, stress levels, general health, etc? How is it that some people can have a serious illness such as cancer and recover completely, seemingly miraculously. Is there such a thing as a "will to live"? The mind/body connection will likely turn out to be an important factor in keeping our immune systems strong and healthy and in helping ourselves to heal when we are ill.

Suggestions to Boost the Immune System

1. Eat in a healthy, balanced way - follow the Canada’s Food Guide to Healthy Eating, focus on fruits, vegetables, whole grains, protein and the specific immune-boosting nutrients
2. Consider taking a multivitamin/mineral supplement, older adult’s in particular mat especially benefit from this.
3. Be physically active-physical activity seems to boost the immune system
4. Get sufficient sleep
5. Be of service to others -Volunteer for someone you like or for a cause you believe in.
6. Have a positive outlook on life - an optimistic outlook may enhance your immune system
7. Reduce stress - unrelieved stress may suppress your immune system. Find ways to reduce stress.
8. Laugh! - Humor can be healing. Norman Cousins has written 2 books on the ability of humor to heal, one based on his own remarkable recovery from a life threatening illness through the use of humor.
9. Do what you enjoy - do work you like and make time for friends and enjoyable leisure activities.
10. Shift your focus to life-live fully each and every day
11. Explore the spiritual-prayer for oneself and for others and spiritual belief seem to have healing benefits.
12. Consider complementary health care practices, e.g. Massage, yoga, tai chi, therapeutic touch, meditation, visualization, individual counseling, support groups. Visualization, for example has been used by many cancer patients where they visualize their own immune system successfully fending off the cancer

Appendix A
Nutrients That Are Important To Your Immune System
And Some Foods That Contain Them

Protein

• Meat
• Chicken, turkey
• Fish, seafood (fresh, frozen or canned)
• Eggs
• Pulses, tofu
• Nuts, peanut butter
• Milk, cheese, yogurt

Iron

Best Sources:

• Liver from beef, pork, chicken, calf
• Kidneys
• Beef, pork, veal, lamb
• Trout, mackerel, clams, sardines, shrimp
• Cooked oysters, scallops
• Pulses, tofu
• Egg yolk
• Turkey (especially dark meat)

Other Sources: absorbed better if eaten with "best sources" of iron or foods, which contain vitamin C

• Whole grains
• Cream of wheat cereal
• Iron-enriched breakfast cereals
• Iron-enriched pasta
• Iron-enriched baby cereals
• Leafy green vegetables, broccoli, peas
• Potatoes, sweet potatoes (with skin)
• Canned tomatoes, tomato juice
• Dried figs, prunes, dates, peaches, raisins
• Nuts, seeds

Vitamin A (carotene)

• Liver
• Milk
• Eggs
• Peaches, apricots, mango, papaya, cantaloupe
• Green vegetables, carrots, sweet potatoes
• Pumpkin, squash, red and green peppers, tomatoes

Copper

• Liver, kidney
• Shellfish
• Pulses
• Nuts
• Whole grain, wheat germ
• Mushrooms

Magnesium

• Seafood
• Pulses, tofu
• Milk
• Whole grains, wheat germ, bran cereals
• Green leafy vegetables, avocado, broccoli
• Green peas
• Baked potatoes (with skin)
• Bananas, raisins, dried figs, dates
• Nuts, seeds

Selenium

• All liver
• Seafood
• Beef, pork, veal, lamb, chicken
• Milk, cheese, yogurt
• Whole grain, wheat germ
• Pulses

Zinc

• All livers
• Beef, pork, veal, lamb
• All seafood, sardines, herring
• Leafy green vegetables
• Pulses
• Peanuts, seeds, nuts
• Whole grain, wheat germ
• Eggs
• Milk, cheese, yogurt

Vitamin B6 (pyridoxine)

• Liver, meat
• Chicken
• Fish
• Whole grains, wheat germ
• Pulses
• Bananas
• Baked potatoes (with skin)
• Spinach, avocados, green peas

Vitamin B12

• Liver, meat
• Chicken, turkey
• Fish
• Eggs, milk, cheese, yogurt

Vitamin C

• Citrus fruits, kiwi, strawberries, other berries, cantaloupes, papaya, mangoes
• Leafy green vegetables, broccoli, cauliflower, cabbage, all peppers, tomatoes, potatoes
• Snow peas

Vitamin E

• Almonds, sunflower seeds, peanuts
• Leafy green vegetables
• Whole grains, wheat germ
• Safflower oil, sunflower oil, corn oil, wheat grem oil

Folic Acid (folate)

• Liver, kidney
• Pulses
• Oranges, cantaloupe
• Leafy green vegetables
• Cabbage, corn, green peas, avocado
• Whole grains, wheat germ
• Sunflower seeds, nuts, peanuts

Essential Fatty Acids

• Corn oil, sunflower oil, soy oil, flaxseed oil, safflower oil, wheat germ oil
• Wheat germ

Pulses:

Adzuki beans, black beans, white beans, fava beans, kidney beans, lima beans, mung beans, navy beans, pinto beans, soybeans, flageolets, lentils (brown, red or green), black eyed beans, chickpeas, field peas, pigeon peas, split peas

Spinach, romaine lettuce, Swiss chard, escarole, watercress, kale, collards, beet green, parsley (less rich in calcium than the others)

Whole grain breads, whole grain pasta, hot and cold whole grain cereals (check the labels), brown rice, millet, whole wheat couscous, barley, buckwheat, bulgur, rye, oats.