An overactive immune response, which can occur with viral infections, could result in sudden hair graying, according to research in mice. The research revealed that a molecule involved in hair pigmentation also controls certain immune system genes. The study cannot explain why a fright or severe illness might lead to rapid graying, but it may provide insights into the skin condition vitiligo, an autoimmune disorder in which the skin loses its color, and melanoma, a cancer of skin pigment cells, the study team writes in PLoS Biology. “All of this work was done in mice, and so we are hesitant to make too many inferences to humans without further experimentation,” said lead author Melissa L. Harris from the University of Alabama at Birmingham. “However, we would love to test whether the mechanism in this study could explain those anecdotal stories where people experience premature gray hair,” Harris said in an email. “Could the combination of a genetic predisposition and an everyday viral infection be just enough to negatively affect the melanocytes and melanocyte stem cells in humans, and cause early hair graying?” Hair color depends on melanocyte stem cells that live at the base of hair follicles. As old hairs fall out and new hairs grow in, these cells develop into melanocytes - cells that produce the pigment that gives hair its color. When the stem cells are lost, new hair that grows turns out to be gray. Harris's team earlier found that a protein called MITF, which controls a number of genetic pathways in these melanocyte stem cells, is involved in hair graying in certain mice. In the current study, they found that MITF also limits the activity of certain genes that control the immune response to viruses. Mice with mutations in the gene for MITF have an overactive response to viruses that results in the loss of melanocytes and melanocyte stem cells in the hair bulb, and this results in hair graying, the study team reports. Although it's too early to know for sure, people with similar mutations in this gene could show a similar response, resulting in spontaneous hair graying after a viral infection, they write.
Because MITF turns out to be a “critical suppressor of innate immunity” and can cause loss of pigment producing cells, there may be implications for understanding vitiligo as well, the authors conclude.
