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Know Your Enemy

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By Hsei Di Law

New research has revealed a key mechanism by which our immune system turns against us.

Hsei Di Law is a research technician at the John Curtin School of Medical Research, The Australian National University.

The full text of this article can be purchased from Informit.

Letter for letter, every single 75 trillion of your cells has identical DNA. However, one group of cells not only has DNA that reads differently to every other cell of the body, but also differently from one another. These are a type of white blood cell known as B cells.

B cells have a central role within the immune system. They are the ones responsible for producing antibodies – the molecules that fight off infections. One estimate says that a single B cell can secrete more than 2000 molecules of antibody per second.

What is also unique to B cells is that the letters of their DNA have been deliberately scrambled. It is a cell’s natural impulse to protect its DNA sequence tooth and nail, making this feature of B cells a remarkable and curious phenomenon.

B cells are constantly being formed in the bone marrow. In each developing B cell, a pair of enzymes homes in on the region of DNA that encodes antibody molecules. Here they act together to randomly cut out and rejoin bits and pieces of DNA.

This scrambling of the DNA creates millions of random combinations of sequences. What results is a troop of B cells, each of which possesses a different DNA sequence for antibodies. Thus each and every one expresses a different and unique kind of antibody.

Owing to this process of randomising DNA, each of us has millions of different antibodies...

The full text of this article can be purchased from Informit.