The immune response is your body's way of recognising and defending itself against bacteria, viruses, and other potentially harmful substances. Antigens are recognised and responded to by the immune system, which defends the body from potentially hazardous chemicals. Antigens are substances on the surface of cells, viruses, fungi, and bacteria that are usually proteins. Antigens include non-living entities such as poisons, chemicals, medications, and foreign particles (such as a splinter). Antigen-containing compounds are recognised by the immune system, which destroys or attempts to destroy them. Inflammation is one of the major mechanisms that alerts the immune system, but when this mechanism is disrupted, a long-term chronic inflammation develops, which is likely to be harmful to the host. An imbalance of circulating inflammatory chemicals is associated to the majority of age-related illnesses.