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Basics of the Immune System   
Date:
June 10, 2005 03:01 PM
Basics of the Immune System by Leonid G. Ber, MD Energy Times, September 1, 1998 In a world filled with pathogens and microbes, good health and resistance to disease is no accident. It requires a vigorous and vigilant immune system. The immune system should be viewed as an internal security force that is constantly checking the identity of everything entering and already existing in the body. A cell or substance may be recognized as "non-self" and a potential enemy if it does not have the right molecular make-up. A cell displaying molecules produced according to a different blueprint than the body's own code may be recognized as foreign. To eliminate alien material that may harm the body, the immune system must take swift action. Recognizing entities that originate outside the self forms the key to overall immune system response. This key is carried in the body by cells called macrophages (ma-kro-fajs), a name derived from a Greek term meaning "big eater." Macrophages eat or engulf foreign cells and molecules. When a macrophage encounters something that it distinguishes as being "non-self" or abnormal, it can attack the enemy with a series of assault weapons, including free-radicals (reactive substances) and enzymes, that dissolve and weaken the intruder. In fact, an enzyme produced by macrophages called lysozyme is recognized as one of nature's most powerful anti-infective agents. These chemical defenses, along with engulfment and complete digestion by macrophages, can effectively stymie invasion by disease-causing pathogens. Disease Invasion Harmful invasion can originate in the body's own cells as well as begin from outside sources. While we are constantly exposed to bacteria, viruses, fungal cells and parasites, destructive cancerous growths often start within the body. Every day, thousands of the body's cells mutate into possible cancers. Under most circumstances, the immune system keeps these cells under control. But when the immune "security" system slips up, these harmful growths multiply unrecognized. Getting Specific The initial immune response that recognizes invaders is called a "non-specific defense mechanism" since this immune response is generally the same toward all invaders. This counter-attack entails battling every invader pretty much identically: a macrophage can engage, dissolve, weaken, engulf, digest, eliminate. However, if, despite the initial immune efforts, the problem persists, a macrophage can tag an invader and "introduce" it to the rest of the immune system, thus recruiting more specialized types of immune cells to enter the battle. This tagging function endows macrophages with the name "antigen-presenting cells." (Antigens are substances that can provoke specific responses by the immune system.) Most antigens are proteins. Proteins are relatively large molecules made of smaller units called amino acids. The specific geometric organization of amino acids is what conveys uniqueness to each protein. (Your genetic code forms a blueprint for the production of your own, individual proteins.) Protein molecules produced by one human being can act as an antigen for another human being. That's why organs transplanted from one person to another can be rejected by the immune system. Unless organs are transplanted from one identical twin to another (who share the genetic blueprint for protein creation), doctors must use immune-suppressing drugs to curtail organ rejection. At the same time as these medicines prevent transplant rejection, they also make people more susceptible to infectious diseases and cancer. Specialized Immunity After one set of immune cells chemically tags antigens (invaders) for recognition, other highly specialized parts of the immune system go into action: Cells called T cells or T lymphocytes acknowledge the invaders and can take the further action (second line of defense) that is necessary to render them harmless. T cells get their name from the thymus (an organ located behind the sternum) where they originate. The thymus, most active when we're young, usually shrinks and apparently slows or shuts down its activity about the age of forty. A wide variety of T cells inhabit lymph nodes (soft, usually round, pea- or nut-sized organs) and other body areas. For instance, natural killer cells, as their name implies, are a particularly aggressive type of T cell. Another type of T cell is called T helper (a cell that supports development of immune response). T suppressors halt immune response when infection ends. In order to make all these different cells work in concert, cytokines or messenger molecules are produced that facilitate constant communications between all the parts of the immune system. The B Team Other organs of the immune system include: *bone marrow: a powerful cell producing organ where the majority of immune cells are born; *spleen: an abdominal organ that forms a reservoir for the production of immune cells. Lymph nodes oversee particular segments of the body where they collect and recycle tissue fluids. Like an early warning system, lymph nodes react when an invader is detected in the part of the body that it controls. Yet another step in the so-called immune cascade entails action by lymphocytes, called B cells, which originate in the bone marrow. These cells produce antibodies which are immune proteins (immunglobulins) that attack specific antigens. While traveling in the blood, an antibody can bind to an antigen, curtailing its harmful action. This bound up molecule forms a complex easily recognized by scavenging macrophages which make a quick meal out of the unlucky invader. After enemy cells are removed from the body, knowledge of this victory resides in the immunological memory prolonging your resistance toward specific disease pathogens indefinitely. That's why someone who has recovered from a disease like the measles may be impervious to reinfection. Rules for Optimum Immunity Even though the immune system consists of a complex team of hard-working cells, enhancing your immunity is relatively easy: Maintain a healthy lifestyle. Avoid continuous stress and negative emotions or cope with them through exercise or meditation. Consistent, moderate exercise can boost the immune system. Massage can also help although extreme care must be taken when inflammation or disease is already present. Sleep 7-8 hours a day. Sleep allows the body to recover and rebuild. Protein synthesis, vital for a healthy immune system, increases during the night. Stick to a healthy diet. Your immune system consists of trillions of cells. Consequently, nutrients important for cell health boost the immune system. A balanced low-calorie diet rich in complex carbohydrates, "good" fats (including fish oils, olive oil and flaxseed oil) along with vitamins, minerals and phytonutrient antioxidants from fresh fruits and vegetables can fortify immune cells. Plus, drinking plenty of water helps improve circulation of lymph fluid. These recommendations are not hard to meet once they become a part of your daily routine. However, extra immune security may be necessary during flu season, while traveling long distances (airplanes are notorious sources of pathogens) or when working extensive hours in front of a computer screen. In addition, exposure to x-rays, immunosuppressive chemicals, ultraviolet radiation (the sun) or simply aging may give your immune cells extra burdens. Your "specific" immune system does not respond immediately to the challenge of invasion by an infectious organism. Instead, it may require about 2 weeks for an effective reaction after antigen recognition and alerting T cells. During this period, the macrophages' non-specific defense assumes a crucial role in keeping infection in check. Enhanced activity by macrophages is especially important for recognizing and destroying cancer cells. The most dangerous cancers are those that can mimic normal cells and avoid the immune system's wrath. Few substances can activate macrophage function in the body (aloe vera contains substances that contribute to this process). The most powerful macrophage activator recognized by the scientific community is a sugar-like substance called beta-1,3-D-glucan. Beta-glucan, extracted from the cell walls of common Baker's yeast, when taken in certain small amounts, can prevent infection by making macrophages more active in recognizing and attacking infectious bacteria, fungi and certain viruses. This kind of activation can encourage macrophages to attack previously unrecognized tumor cells. As a result, tumors may be eradicated as the immune system mobilizes and produces what may be known as "spontaneous healing." Hungry Macrophages When a macrophage works overtime fighting disease, its demand for nutrients and energy increases dramatically. Vitamin C, known for its immune supporting function, seems to be especially important for maintaining fully active macrophages. Vitamin C collects in macrophages, often reaching forty times the concentration found in surrounding blood. What are conventionally considered normal amounts of vitamin C in the body may be insufficient to keep macrophages well supplied with this antioxidant. Therefore, extra amounts of vitamin C can keep the immune system in fighting trim. Scientists are only now beginning to uncover the secrets of the highly organized immune system. One thing's certain: The immunity security team depends on proper lifestyle, nutrition and supplements to maintain the critical defenses necessary for good health. Dr. Ber received his doctorate in internal medicine from the Yaroslavle, State Medical Institute in Yaroslavle, Russia.
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