The immune system is the most dynamic indicator in determining our overall health and wellbeing. A very complex and capable network responsible for defending us against germs that are trying to invade us daily, it plays a vital role in keeping us healthy. It is on constant alert to determine what’s friend or foe, what’s foreign and what’s not and then responding accordingly.The immune system is made up of specialised cells, tissues and organs. Important among these are the white blood cells of which there are different types with different life spans, from a few hours to a few days. Millions develop everyday in bone marrow, made up of shimmering little granules that look similar to granules of sugar. In a healthy immune system, the granules vibrate and this movement gives the cells ’legs’ so they can walk around and patrol the body, destroying germs as soon as they enter. If the granules don’t vibrate, e.g. because of nutritional deficiencies or damage to the lining of the gut, then the immune system can’t patrol as efficiently. A healthy immune system needs a variety of good bacteria to fight the bad bacteria or pathogenic bacteria that can make us sick. The bad bugs can enter the body via contaminated food or we can pick them up or ‘catch’ them.Natural immunityNatural immunity also known as innate immunity or non-specific immunity is a mechanical barrier and the first line of defence against bad bacteria. It is the protection provided by the skin, respiratory tract (lungs) and in the gut wall. For example, actions such as coughing and sneezing are the immune system’s way of expelling the virus or bacteria from the nose and throat. Tears clear the eyes of dust and other irritants, while diarrhoea and vomiting are mechanical methods for expelling unwanted germs from the gut.Acquired immunityAcquired immunity develops through exposure to specific germs and these are remembered by the body’s immune system. When the same bacteria enters the body again, the immune system remembers how to respond to them, such as with chickenpox. For example, once a child is exposed to chickenpox, the immune system will produce white blood cells called antibodies that will destroy the chickenpox virus. When your child is exposed to chickenpox again, the immune system is primed and knows how to fight the virus.Antibodies are part of the immune system found in the bloodstream. They are large Y-shaped proteins that circulate in the blood and are recruited by the immune system to detect and destroy foreign invasion from bacteria and viruses.Antibodies can attach themselves to the bacteria or virus at the top of the Y-shape and this inactivates or kills the germ. They also attract other immune system cells to destroy the invading germ.