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antigen vs. antibody

antigen vs. antibody: What’s the difference?

Antibodies are proteins that act as immune system defenses. Antibodies attack antigens, which are things like viruses, bacteria, toxins, cancer cells, and other foreign substances, like the cells of a transplanted organ. In other words, an antigen is anything that causes the body to produce antibodies.

[ an-ti-juhn ]
  1. any substance, as a protein, carbohydrate, etc., that, on entering the body, can stimulate an immune response and combine with a specific antibody or T cell receptor having a matching molecular structure.
  2. any commercial substance, usually synthetic, that stimulates the production ofantibodies when injected or absorbed into animal tissues.
  3. antigens of a particular type collectively.
[ an-ti-bod-ee ]
  1. any of numerous Y-shaped protein molecules produced by B cells as a primary immune defense, each molecule and its clones having a unique binding site that can combine with the complementary site of a foreign antigen, as on a virus or bacterium, thereby disabling the antigen and signaling other immune defenses. Abbreviation: Ab
  2. antibodies of a particular type collectively.

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