Legend has it that fright, stress, or grief may drain the color from one’s hair overnight. Nothing quite like this phenomenon has been confirmed by science, though gradual hair graying has been studied to uncover mechanisms of stem cell self-renewal. For example, hair graying in mice has been associated with the premature differentiation of melanocyte stem cells (McSCs) and their eventual depletion. Now, in a new study from researchers at the National Institutes of Health (NIH) and the University of Alabama, hair graying has also been associated with dysregulation of the innate immune system.

Both hair-graying associations—premature McSC differentiation and immune dysregulation—have a common link—the melanogenesis associated transcription factor, or MITF. This transcription factor, it turns out, does double duty. It affects both the genes that affect hair color and the genes that notify our body of a pathogenic infection.

When a body is under attack from …