when the body is invaded by antigens, the immune system forms substances called
Antibodies, also called immunoglobulins, are proteins manufactured by the body that help fight against foreign substances called antigens. When an antigen enters the body, it stimulates the immune system to produce antibodies. (The immune system is the body's natural defense system.) The antibodies attach, or bind, themselves to the antigen and inactivate it. Every healthy adult's body has small amounts of thousands of different antibodies.