The immune system is composed of special organs, cells, and proteins that work together to protect the body from infections and other potential harm. It has an important role in protecting us against disease-causing microorganisms and foreign substances. Its primary purpose is to identify and destroy any harmful organisms or substances while simultaneously preserving beneficial living things. The most important part of the immune system is its ability to distinguish between self and non-self molecules, also known as antigens; it can identify any foreign substance or pathogen that enters the body as a threat and launch a response to fight them off. This requires precise coordination among various cells, organs, hormones, proteins, antibodies and other components of the immune system.