For years، gray hair was associated with old age، but there are some people who would get premature gray hair at a young age. Others have stated that their gray hair came from a sort of tragedy or the daily stress of life، as the Technical Times said. However، a new a new study shows that getting gray hair may stem from a person's immune system. In a test conducted on mice، researchers at the National Institutes of Health and the University of Alabama، Birmingham showed that an overactive immune response can lead to gray hair. The study revealed that a molecule that is involved in hair and skin pigmentation also controls certain immune genes. The authors of the study stated that when a body is under attack from a virus، the innate immune system kicks in to fight it. Cells in the body have the ability to detect any type of foreign invader and the respond by producing interferons، which are signaling molecules. Interferons then signal other cells to take action against the viral infection. Hair color is linked to the melanocyte stem cells found in hair follicles. When a person loses their hair and grows it back، melanocyte stem cells serve as a supply for the melanocytes، which are cells that produce a pigment called melanin. Without these cells، hair will turn a gray color. The researchers that conducted this study tested the gray hair in mice، which is how they discovered the link between the innate immune system and the MITF factor، a protein that also keeps interferon in check. For the mice، if the MITFs control on the interferon response was lost in the melanocyte stem cells، the hair on the mice turned gray. The experiment also showed that when the innate immune system was activated، it increased the gray hair in mice that were predisposed to already getting it. The lead researcher of the study، Melissa L. Harris، stressed that these findings were done on mice. Therefore، more research is needed before it can be assumed this also happens in humans. "All of this work was done in mice، and so we are hesitant to make too many inferences to humans without further experimentation،" Harris stated. The new study does، however، shine some hope in pigmentation diseases such as vitiligo، which is a condition that causes discolored skin patches.