The immune response is how your body recognizes and defends itself against bacteria, viruses, and substances that appear foreign and harmful to the body.
The immune system protects the body from potentially harmful substances by recognizing and responding to antigens. Antigens are molecules on the surface of cells, viruses, fungi, or bacteria. Non-living substances such as toxins, chemicals, drugs, and foreign particlesImmuneResponce can be antigens.
Even your own body cells have protects that are antigens. These include a group of antigens called HLAantigens . Your immune system learns to see these antigens as normal and does not usually react against them.