The mice were genetically engineered to react like a person with a cat allergy. They wheezed and got watery eyes when there was a cat around.
. . .
[Dr. Saxon] injected the allergic mice with a protein that combines cat and human proteins. He used very small doses over time. The mice’s immune systems learned to stop reacting to cat chemicals, and they were cured.
Link. The next step is, of course, creating mice that can defeat cats in battle. Tear it. Tear it up.
Indexed by tags science, cats, mice.