What is an Antibody?

An antibody is a Y-shaped protein. It contains two light chains of amino acids and two heavy chains (see the protein unit in the "Cells Are Us" module).

In theory, there could be some 10³⁰ antibodies, one for each of the multitude of potential antigens that our bodies might be exposed to. But if we only have about 30,000 genes, how could our body make so many antibodies?  The answer is that most of every antibody is the same, with only the extremities of the molecule being variable. And, genes on three chromosomes work together in various ways to make an antibody. The "one gene-one protein" idea does not apply to antibodies.

Circulating antibodies are actually manufactured and released by a so-called "B-cell" white blood cell. These cells are made in the bone marrow and migrate out into blood and  lymph (a filtrate of blood that has its own circulatory system, moving through lymph nodes). The antibodies released by B-cells find circulating proteins from bacteria, fungi, or viruses, and inactivate them.

Once antibodies are triggered, it is time for the white blood cells to move in.

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