b'CHAPTER ONEThe Secret Life of Your Immune SystemA n effective immune system is made up of a variety of cells, each with a specific duty. A huge army of white blood cells known as phagocytes and lymphocytes are among the most important components of a healthy immune system. Some phagocytes, called macrophages, constantly patrol your body, destroying germs as soon as they make an appearance. Macrophages also produce tumor necrosis factor (TNF), which kills some types of tumor cells, tames inflammation, and triggers the creation of new blood cells. If an infection begins to take hold, your body fights back with even more powerful B-cells and T-cells. B-cells identify harmful bacteria and also remember certain pathogens that have made you sick in the past. T-cells, on the other hand, are the foot soldiers that destroy the bad actors that the B-cells have identified. One specialized type of T-cell is the powerful natural killer (NK) cell that can eradicate certain tumor cells and virus-infected cells.Your lymph system also plays a role in your immune response. As the bodys drainage system, it filters excess bodily fluid through the lymph nodes and transports it back into blood circulation. During this process, harmful organisms are trapped and destroyed by lymphocytes. The lymph system also makes antibodiesspecialized proteins produced in response to an invasion by a virus, bacteria, or other foreign substance. Antibodies then render the invading antigens harmless.Immunity at Every AgeThe immune system changes during the aging process. For example, childrens immune systems dont fully develop until theyre seven or eight years old. Thats why infants are more susceptible to ailments like croup or ear infections and why young children seem to catch every little bug going around their school or day care. By the time children reach their teen years, their natural immunity is fairly robust. But their immune response can be undermined by typical teenage habits: a poor diet filled with junk food, a lack of exercise, and a lack of sufficient sleep. The same goes for young adults trying to juggle the demands of work, kids, and a social life. Pregnancy can also impact immunity. According to research in the journal Frontiers in Immunology, the risk and severity of infection increase during pregnancy. This is, in part, because the immune system makes changes to prevent the mothers body from rejecting the fetus.Perhaps the biggest changes to the immune system occur after age 60. These age-related changes to the immune system are known among researchers as immunosenescence. A lifetime of wear and tear contributes to these age-related immune changes. Plus, exposure to environmental contaminants over the years can further undermine the immune system. As you can see, each stage of life carries its own risks to your defenses. However, taking steps to support a healthy immune response throughout your life can help keep you healthy at every age, no matter what your immune system encounters. 4OPTIMAL IMMUNIT Y'