Curing TB with sunlight

Ultraviolet (UV) light makes vitamin D, and vitamin D turns on innate immunity to tuberculosis (TB), say Steffen Stenger (Universität Erlangen, Germany), Philip Liu, Robert Modlin (University of California, Los Angeles, CA), and colleagues. The lower absorption of UV light by African Americans, leading to lower vitamin D levels, may be one reason why this group is more susceptible to TB.

Chemicals from bugs turn on the innate immune response via Toll-like receptors (TLRs). Modlin had already found that activating TLRs killed off intracellular Mycobacterium tuberculosis. Nitric oxide (NO) was the downstream mediator for this in mouse cells, but “we've been grasping for a decade to find a mechanism in humans,” says coauthor Barry Bloom (Harvard School of Public Health, Boston, MA).

The answer came from gene arrays. Active TLR turned on production of both...