Baldness and immunity
Scientists have uncovered an unusual link between immunity and hair growth
The cause of early baldness or problems with hair growth may be not only an excess of testosterone, but also the malfunction of immune cells, according to an article published in the journal Cell (Ali et al., Regulatory T Cells in Skin Facilitate Epithelial Stem Cell Differentiation – VM).
"Our hair follicles are constantly being recycled: when the hair falls out, the entire structure of the bulb must actually grow anew. We always thought that the course of this process depends solely on the stem cells themselves, but it turned out that regulatory T cells play a key role in this process. If you turn them off, then the hair just stops growing," explains Michael Rosenblum from the University of California at San Francisco (in a press release, Faulty Immune Cells May Play a Role in Alopecia, Other Forms of Baldness – VM).
A picture from an article in Cell – VM.
Many men and some women often begin to lose hair on the forehead or crown in middle age and often become partially or completely bald by the age of 40. As experiments and observations of recent years show, baldness is caused by two sets of causes: the improper operation of male hormones that suppress the work of cells in hair follicles, and mutations in genes that control the growth of hair on the face and other parts of the body.
Rosenblum and his colleagues found another unexpected participant in this process by observing what special immune cells are doing, which constantly live inside the skin and actually never leave its limits.
To find an answer to this question, scientists raised a special breed of mice, whose immune cells they could kill at any point of the body by injecting a toxin produced by bacteria – causative agents of diphtheria. Using these mice, the scientists tried to get areas of skin cleared of immune cells in a similar way.
These experiments led to unexpected results – when biologists shaved the backs of rodents for better access to their skin and left them in a cage for a few days, they noticed that the hair on the shaved areas simply stopped growing. This intrigued Rosenblum and his colleagues, and they continued to observe the "bald" rodents for several weeks, during which the hair on the backs of the animals did not appear.
This led biologists to believe that immune cells may play a critical role in hair growth. To test this idea, the scientists made the immune cells of the skin and the stem cells of the hair follicles glow and tracked their relationship using microscopes.
It turned out that the so-called regulatory T cells were directly involved in hair growth. They produced chemical signals, Jag1 protein molecules, which caused the stem cells of the bulb to grow and form a new hair.
This "skill" of immune cells, as further experiments showed, was not related to their main functions – protecting the skin from the development of inflammation. According to scientists, this indicates the joint evolution of this kind of immune cells and mammalian hair, unable to grow again without their help.
According to Rosenblum, disorders in the work of T cells may be associated with the development of some forms of baldness in people with normal testosterone levels and disorders in skin regeneration when wounds and scratches are tightened.
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26.05.2017