THE creation of a lab rat with no functioning immune system is opening up the possibility of more realistic testing of cancer treatments, transplantation techniques and other therapies. Such animals are useful to researchers because the immune response in a normal animal can complicate test results.
Until now, mice have been the only lab animals readily available with no immune system. They are produced by knocking out key genes in mouse embryonic stem cells required for the immune system to function. Development of a rat equivalent has lagged behind, as the first 鈥渒nockout rats鈥� were not engineered until late last year.
Now researchers at of Lexington, Kentucky, have announced that they have made what they call a 鈥淪CID rat鈥� 鈥� so called because the animal鈥檚 lack of an immune system leaves it with a condition resembling a human syndrome called severe combined immune deficiency. The SCID rats were made by mutating embryonic DNA in a way that 鈥渟witched off鈥� the immune system.
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The SCID rats will aid research into human illnesses because rats are more closely related to humans than mice, so experiments on them give a better idea of what may happen in people. A mouse鈥檚 heart beats 5 to 10 times as fast as a human鈥檚, whereas a rat鈥檚 heart rate is closer to ours. Because rats have similar liver enzymes to humans, they clear poisons in the same way. And because rats are intelligent, future knockout rats could be used for research on memory, learning and neurological disease.
Rats are also 鈥渟mall enough to be cost-effective and easy to breed鈥�, says Eric Ostertag, Transposagen鈥檚 founder and CEO.
Ostertag predicts that as well as having practical potential in immunology, cancer research and transplant research, the SCID rat鈥檚 significance stretches even further. It also heralds the arrival of many other types of knockout rats vital for research, he says.
