The Rogue Immune Cells That Wreck the Brain

In the first years of her career in brain research, Beth Stevens thought of microglia with annoyance if she thought of them at all. When she gazed into a microscope and saw these ubiquitous cells with their spidery tentacles, she did what most neuroscientists had been doing for generations: she looked right past them and focused on the rest of the brain tissue, just as you might look through specks of dirt on a windshield. "What are they doing there?" she thought. Stevens never would have guessed that just a few years later, she would be running a laboratory at Harvard and Boston's Children's Hospital devoted to the study of these obscure little clumps. Or that she would be arguing in the world's top scientific journals that microglia might hold the key to understanding not just normal brain development but also what causes Alzheimer's, Huntington's, autism, schizophrenia, and other intractable brain disorders. Microglia are part of a larger class of cells--known collectively as glia--that carry out an array of functions in the brain, guiding its development and serving as its immune system by gobbling up diseased or damaged cells and carting away debris.