When it comes to bacteria, many people have a pretty simple view: Germs are bad, and our lives should be as free of them as possible.
But an alternate idea suggests just the opposite: Germs are a necessary part of a healthy immune system, helping our body's defenses beef up and fight future illnesses. When a person's exposure to germs is decreased, problems may arise.
Researchers at Brigham and Women's Hospital in Boston studied two kinds of mice: One group had been exposed to a normal bacteria environment, and another group that was germ-free. When scientists compared the immune systems of the two groups of mice, they found what they cited as evidence to support the hygiene hypothesis – the mice that had been exposed to microbes had stronger immune systems than the germ-free mice.
Additionally, the germ-free mice had exaggerated inflammation in their lungs and colon, similar to what is seen in humans who have asthma and ulcerative colitis. The researchers found that a particular kind of immune cell, called an invariant natural killer T cell, was particularly hyperactive in these mice.
But all was not lost for the germ-free mice. When the researchers introduced them to microbes in the first few weeks of their lives, their fragile immune systems beefed up to a normal level. But older germ-free mice didn't get this beneficial effect.
The results were published today in the journal Science. --ABC News
