Protect first line of defense Published March 22, 2013 By Senior Airman Kate Vaughn 56th Fighter Wing Public Affairs LUKE AIR FORCE BASE, Ariz. -- The body's immune system is the first line of defense against harmful bacteria, viruses and infections. Some well-known methods of keeping the immune system strong include maintaining a healthy weight and diet, and getting plenty of sleep. Rachel Perkins-Garner, 56th Medical Group registered nurse, said there are also plenty of ways the immune system can be weakened. "Your immune system can be depressed when receiving blood transfusions, surgery, malnutrition and stress." Perkins-Garner said one of the most important parts of keeping the immune system strong is getting the right amount of physical activity. "Staying fit is vital to maintaining a healthy immune system," she said. "Try to incorporate different types of exercise as well. Include cardiovascular, strength training and work on flexibility." The University of Nebraska Medical Center recently conducted a study led by Laura Bilek on the immune systems of a group of cancer survivors. Sixteen participants gave blood and saliva samples before and after exercising moderately each day. "Analysis showed that a large portion of the immune cells changed from a senescent (aging) form to a naïve form," said Bilek. "This means that they went from a form that is not as efficient in fighting against cancer to a form that is prepared to protect against disease and infections." The Cleveland Clinic Foundation says that a low amount of exercise could be enough to keep immunity up. Even relatively low levels of aerobic exercise can protect your immune system, according to the CCF website. "Twenty to 30 minutes of brisk walking five days per week is an ideal training program for maintaining a healthy immune response," it stated. However, the amount of exercise performed can dramatically change the immune systems functions. Moderate exercise is said to boost the immune system, but extreme or strenuous exercise can have the opposite effect. One study conducted by the National Center for Biotechnology Information tested the immune systems of 24 professional soccer players before and after a 90-minute match. The study found the immune system shifted significantly after play. "Before play, the saliva of most of the players showed normal levels of immunoglobulins, substances that help to fight off infection," according to the NCBI. "Afterward, concentrations of saliva immunoglobulins in many of them had fallen dramatically." Exercise has many health benefits, but knowing how the body reacts to different types of activity can mean the difference between catching a cold and staying flu-free. For more information about building a strong immune system, visit www.cdc.gov.