An antigen is a foreign substance that enters the body, such as bacteria, viruses, fungi, allergens, venom, and toxins. On the other hand, an antibody is a protein produced by the immune system to attack and fight off antigens. When an antigen enters the body, the immune system recognizes it and produces antibodies to eliminate the antigen from the body. Antibodies are Y-shaped proteins that bind to specific antigens, neutralizing them or tagging them for other parts of the immune system to eliminate. Antigens trigger the immune system to launch an antibody response, and specific antibodies detect and neutralize specific antigens
. Antigens and antibodies play vital but distinct roles in the immune system. Antigens cause disease, while antibodies fight them. Antigen tests look for active infections, whereas antibody tests look for signs of past infections
