Human life, it would be faced with a wide range of environmental environment and inappropriate. And the environment, or it may cause harm to humans, such as microorganisms, chemical, small creatures, dust, etc. Therefore, man's body is essential to the immune system. To help combat and eliminate foreign substances that enter the body. So that humans can survive in the environment at a normal life. And have a strong, healthy body , we call that a foreign substance into the human body as antigens (antigen), a substance or organism when entering the body. Will affect the response of the body or cause disease in humans. The human body needs a response mechanism for the removal of these foreign bodies. To the work of the various systems in the body can proceed normally. We call the system within the body that acts against foreign and disorders that are caused by the body. Called Immune system.