Gut Microbes Keep Rare Immune Cells in Line

 The idea that exposure to microbes can be good for us—by tuning up our immune systems and preventing overreactions like asthma and autoimmune diseases—is catching. Now, a new study of this provocative notion, known as the hygiene hypothesis, suggests that microbes furnish some of their benefits in an unexpected way. Researchers have found that the typical intestinal bacteria in mice rein in a rare type of immune cell, curtailing asthma and colitis in the rodents. Scientists following the long-running discussion over the hygiene hypothesis give the new work, reported online in Science this week