Standardised mice

Press, 5 March 1982, Page 14

Standardised mice

From ‘The Economist’, London.

Science Spot

Much of the pure research that involves animals is done on quite exceptional beasts carefully bred over many years—above all, inbred strains of mice. The point of inbreeding? You can produce animals that are like identical twins. And ones that generation after generation, have particular characteristics. The existence of inbred strains of mice with predictably high or low incidences of certain types of cancer helped enormously in the research that led to the discovery of the existence of viruses that can cause cancer in animals.

Until the early 1930 s it was thought that in animals—and people—the occurrence of different types of cancer was controlled mainly by inherited characteristics. Work with inbred strains of mice made a

nonsense of that theory. Their cancers simply did not follow strict genetic rules. It was clear something else was involved. For a strain of mice known as the C3H strain, the something else turned out to be a virus capable of causing breast cancer in the animals. In the case of a strain known as AK, the culprit, was a virus causing leukaemia. Inbred strains of mice which lack certain of the natural defences that animals normally have against disease have helped speed along scientists’ unfolding of the way the im-

mune system works in people as well as in mice.

The ability to treat individual mice of an inbred strain as if they were identical twins, triplets, quintuplets and so on, has helped to unravel the mechanisms that make an organ transplant work or fail.

Curiously the potential value of controlling the “genetic variable” by extensive inbreeding came to be recognised only slowly. Initially it was assumed that such inbreeding would simply produce sickly, poorly reproducing animals. The pioneers, who decided to go ahead anyway at the start of this century, had a devil of a time.

They attracted ridicule. They sometimes had to go to absurd extremes to keep their precious mouse lines going. One geneticist kept his ■ mice in coffee tins in his room at an American army hospital and in his car. Another had his under his bed while on honeymoon in a tent and later talked his wife into putting up .with having hundreds of the creatures in their house. It was not until 1929 that the first laboratory tackled the job of perpetuating inbred strains. Now researchers in many fields would be at a loss without them. And many people—e.g.; would-be recipients of transplants—would already be dead.. .