Inflammation is a response by the body to injury or infection. Inflammation causes redness, swelling, heat, and pain, and it impairs the function of the affected organ or tissue. The response brings white blood cells called leukocytes, which are part of the body's immune system, to the site of injury or infection. Inflammation, together with the immune system, removes infectious organisms and destroyed or damaged tissues, and begins healing. Chemicals called chemokines and cytokines, released by leukocytes, organize the body's inflammation response.