Some people discover their first white hair at the age of 15, others at 40. We know there is a part of genetics and time that goes by, but what if those weren’t the only reasons? Researchers from the National Institutes of Health and the University of Alabama in Birmingham, USA, have discovered that our immune system plays an important role in the graying of our hair. The results of their research appeared in the journal PLOS Biology.
In the bulb of our hair are melanocytes, cells produced by melanocyte stem cells. Melanocytes make melanin which gives our hair color. These are also the same cells that color our skin. When a hair falls out, the stem cells will make new melanocytes for the new bulb, also called a follicle. With age, stem cells stop working and our hair grows back without pigmentation, so it becomes gray or white. But what is the connection with the immune system?
Too much interferons harm our melanocytes
Our immune system is constantly fighting viruses and bacteria, prompting endangered cells to produce molecules called interferons. These molecules make it possible to indicate to other cells that it is necessary to activate the mechanisms preventing the replication of viruses and bacteria, and also to call the cells “soldier” which protect our body by getting rid of intruders. The researchers found that an excess of interferons affected a certain protein, called MITF, which is necessary for the proper function of melanocytes.
The researchers observed that when a mouse saw its immune system activated, it resulted in a significant loss of melanocytes and melanocytic stem cells, and therefore the appearance of a large number of gray hairs. This reaction could explain why people develop gray hair early on, especially if they have been exposed to many infections since childhood. More studies are needed to understand the underlying mechanisms and to know if the same is happening in humans. But scientists hope their research will help them learn more about diseases that affect depigmentation, such as vitiligo, which affects the pigments of the skin.
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