With modern plumbing and hygiene, the number of nasty microbes we humans are exposed to has plummeted, while the rate of autoimmune diseases and allergies has shot up. Are those related? Proponents of the hygiene hypothesis think so: our immune system is supposed to develop by encountering microbes, so being too clean throws it out of whack as the immune system overreacts to minor insults.
A new study found that mice raised germ-free had especially high numbers of invariant natural killer T cells (iNKT) in their colons and lungs—the mouse versions of inflammatory bowel disease and asthma, respectively. Most evidence supporting the hygiene hypothesis has just been in observed correlations, so this research that identifies a plausible molecular mechanism is good evidence for how over-cleanliness might cause immune dysfunction.
What’s the News: For all the testing we do, drugs are still mysterious things—they can activate pathways we never connected with them or twiddle the dials in some far-off part of the body. To see if drugs already FDA-approved for certain diseases could be used to treat other conditions, scientists lined up two online databases and discovered two drugs that, when tested in mice, worked against diseases they’d never been meant for, suggesting that mining of such information could be a fertile strategy for finding new treatments.