An antibody is a substance produced by lymphocytes in response to an antigen so that it may destroy or control it.
Antibodies can neutralise antigens in a number of ways:
- initiating lysis, or disintegration, of the antigen
- neutralising bacterial toxins
- coating the antigen
- forming a complex to stimulate phagocytosis
- promoting agglutination
- preventing the antigen from adhering to host cells
Typical antigens attacked by antibodies are bacteria, viruses, parasites and dead cells. These types of foreign bodies always give rise to antibodies. However, the first time the body is exposed to an infection, it can take up to two weeks for antibodies to be synthesized. However, after the first infection, subsequent identical infections give rise to antibody production almost immediately. This is the mechanism that underlies vaccination.
Unfortunately, antibodies will also attack transplanted tissue, believing it to be a foreign body. In addition, antibodies can also attack normal healthy tissue, leading to an Autoimmune disorder such as Lupus or Sepsis.