Foreign versus self To protect the body from harmful organisms, the immune system identifies foreign molecules as nonself and destroys those cells Molecules recognized by the immune system are called antigens Antigens are usually protein fragments or carbohydrates during development, the immune system removes components that recognize“ self Immune response to one's own body is called autoimmunityForeign versus Self To protect the body from harmful organisms, the immune system identifies foreign molecules as “nonself” and destroys those cells. Molecules recognized by the immune system are called antigens. Antigens are usually protein fragments or carbohydrates. During development, the immune system removes components that recognize “self”. Immune response to one’s own body is called autoimmunity