Our immune system is the most dynamic body component in determining our state of health or disease. It will be the basis, I believe, of future breakthroughs in medicine. There is a great deal of evidence from current and past research demonstrating life’s effects on human immune function and our immune system’s influences upon our health. These investigations provide a continuous flood of knowledge about the sensitive balance and many levels involved in our wellness. Psychoneuroimmunology, which provides a bridge between psychology and the nervous and immune systems, now plays an essential role in medicine.

Our immune system constantly interacts with our internal environment, protects us from our external environment, and provides the inherent knowledge to sense the difference between friend and foe. For many reasons, including genetics and individuality, some of us may be overactive or too underactive in our defenses, and this can create a great variety of health problems, such as allergies, infections, and cancer.

There are many components to our immune system—organs, bone marrow, cells, antibodies, chemicals, and the nutrients that help nourish and generate them. Most of these cells and tissue constituents are part of what is called in medicine the reticuloendothelial system, which plays a "defensive role in inflammation and immunity" (Dorland’s Medical Dictionary) and in the formation and destruction of blood cells. Our immune system protects us from viruses, bacteria, yeasts and fungi, foreign proteins, and cancer cells. It provides two kinds of protection: Innate (inborn) nonspecific immunity and specific learned or acquired immunity. Specific immunity depends on "humoral" (antibodies and chemicals carried in the blood) and cellular (white blood cells) responses, which can be immediate or delayed.

The thymus-derived lymphocytes (T lymphocytes or, simply, T cells) run the cellular defense and the delayed immune reactions. T cells, specifically T-helper lymphocytes, guide the B cells to produce antibodies (each cell produces only one specific antibody), a process that takes a three-to-five or more days induction period, often the time of infection by new viruses. Reexposure to the same virus will create a more rapid antibody response. This is our important immune memory and there are "memory B cells" that circulate in the blood to respond to subsequent infections. The T-helper cells stimulate immune activity, especially B cell activity, whereas the T-suppressor cells slow down certain functions such as antibody formation, usually after a problem has been handled. Another important cell which is neither a T or B cell or a phagocyte is the NK (natural killer) cell. The T lymphocytes also send messages to (and receive messages from) the macrophages and other phagocytes to "attack" virus-infected cells and foreign organisms, either by engulfing or marking them. Other T cells can also be cytotoxic to virus-infected cells. All of these important T lymphocytes originate in the bone marrow and mature in the thymus gland, the "king" of the immune system. B lymphocytes also originate in the bone marrow and may mature there, in the spleen, lymph nodes, and elsewhere; they are programmed to become the antibody factories or the plasma cells, which are formed from B cells and also produce the specific antibodies.

To explain the entire immune anatomy and interrelationships would take a book or two, but I feel that few other relevant and explanatory notes are important here. The skin and mucous membranes, including the cilia (tiny hairs) lining these membranes and the mucus itself, are all first lines of nonspecific, physical defense by providing a physical barrier against invasion. The lymphatic system is really the secondary circulatory system that removes foreign cells and proteins, which it eventually dumps into the blood to be broken down and eliminated. The lymphatic system itself has no pump, and thus relies on muscle activity and exercise for the lymph to circulate. That is one reason why I believe that physical stagnation increases the chance of infections, and conversely, exercise improves resistance. Lymph nodes are storage sites for cells along the lymphatic system. There are hundreds of these nodes throughout the body. When infection is present, these nodes can commonly be felt in the area closest to the infection. Predominant lymph nodes are in the neck, groin, or axillary regions. The tonsils, adenoids, the appendix, and Peyer’s patches along the small intestine are other important lymphoid tissues. The thymus, bone marrow, and spleen are all sites for immune cell maturation. The liver is also important to immune function, because it helps to detoxify many substances in the body that could be taxing to the immune system.

The phagocytic white blood cells are important in immune surveillance first as the frontline defense patrolling the body. They engulf foreign substances and microorganisms and then can kill or dissolve them by their chemicals. The neutrophils and macrophages work through oxidative destruction. The NK cells kill by secreting a phospholipase enzyme, which dissolves the lipid protection of cells containing viruses or other germs. The NK cells may also release a series of chemicals called interleukins, such as interleukin 2 (IL2), which act as mediators in T lymphocyte functions and proliferation as well as other possible functions. Zinc may help in the production and function of NK cells as well as T and B cells. Besides the basic T and B cells, and the helper and suppressor T cells, and helper-suppressor ratio, special IL2 receptor positive cells and Ta1 positive cells, which are actively dividing T cells, can be measured by specialized T cell or immune system blood studies to reveal the status of current immune functions. Leukotrienes and prostaglandins (E2 series) are other chemicals that are implicated in inflammatory and allergic reactions. More of these are produced when the diet is high in arachidonic acid, found mainly in saturated animal fats.

The complement system releases chemicals in the serum that can lyse, or break apart, antibody-coated cells and microorganisms. Lysozymes and enzymes in tears and saliva can also lyse certain microorganisms. Interferon is an antiviral substance produced by T lymphocytes and macrophages. Iron-binding protein in phagocytic cells also plays a role in protecting against certain infections.

As with other body systems, immune balance is the key. A number of important factors in life influence immune health; unfortunately, there are many more factors that suppress it than enhance it. The basic aging process usually reduces our immune competence. Allergies and infections may do this also, though initially these may stimulate immune activity. Surgery, radiation and chemotherapy, all standard Western cancer treatments, as well as some antibiotic therapy, can weaken immune function, which is not ideal for healing or prevention of cancer in the future. Stress responses, such as that caused by business activity or travel, can lower immunity, as can all varieties of intense emotional and psychological experience. Low self-esteem, emotional extremes, or loss of a loved one may reduce lymphocyte and NK cell numbers and function. Many drugs and chemicals, from steroids (and possibly steroidlike agents, such as excess vitamin D or progesterone) and other anti-inflammatory agents to sugar, alcohol, and marijuana, can be immune suppressors. The external environment can also be detrimental to the normal functioning of the immune system. Photochemical smog, industrial chemicals, pesticides, and certain antibiotic residues in meats as well as a high-fat diet may tax the immune system further. Even excess intake of the polyunsaturated fatty acids (PUFAs) from vegetable oils may increase free-radical formation and affect immunity. Nutritionally, low protein intake and vitamin A and zinc deficiencies are most relevant to immune suppression; a deficiency of essential fatty acids and other essential nutrients, such as pyrodoxine, pantothenic acid, and selenium, may also contribute.