Explanation of Antibodies & Antigens

Antigen and antibody interaction is part of the activities of the body that protect it from infectious disease. When a microbe invades the body, it has antigens on its outer wall. The body's antibodies circulate in the bloodstream and detect these antigens. When attached, antibodies signal the body that an invader is present. The body's immune system sends killer cells like macrophages and T-cells to destroy the microbe and eradicate the disease.

Affinity

• Affinity is the sum between the interactive and repulsive forces between the antibody and the antigen. These two forces determine if the antibody will attach and the likelihood that the two will interact. An antigen and antibody are specific, so the antibody responsible for the flu virus is not the same as the one for a bacterial infection.

Avidity

• Avidity is separate from affinity. While affinity determines the likelihood that an antibody will attach to an antigen, avidity determines how strongly the two will attach. Avidity determines the antibody's ability to stay attached without getting bumped off the antigen by chemicals.

Agglutination

• Agglutination is a diagnosis procedure that uses antigens and antibodies. The connection between the two can be used to detect blood types. If the patient is compatible with a donor, no agglutination occurs. However, if the patient is allergic, the wrong blood treatment causes the immune system to attack the foreign blood. The combination of antibody and antigen causes clumping that is visible in tests.

Specificity

• An antibody has distinct specificity for a certain antigen. The antibody is even capable of distinguishing tiny differences in antigen structure such as isomers, which are small changes in chemical bonds.

Tests

• Antigens and antibodies are used to test human conditions such as pregnancy. Other tests include immunofluorescence, which allows scientists to observe the actions of antibodies by attaching fluorescent compounds on the antibody. The fluorescent component is viewed under a microscope to observe how antibodies react to different antigens.