A study published in the journal Nature Immunology revealed that regulatory T cells interact with skin cells by employing a hormone as a messenger to promote the formation of new hair follicles. It is a well-known fact that alopecia is a hair disorder in which a person’s immune system destroys their hair follicles, resulting in hair loss.

In this study conducted by the experts from Salk, they were initially interested in studying the relationship between regulatory T cells and glucocorticoid hormones in autoimmune diseases, as the former is known to reduce the excessive immune reaction to autoimmune diseases. However, they found that glucocorticoids and regulatory T cells do not function together to play any significant role in autoimmune conditions.

The researchers explained that the upstream hormonal signal and downstream growth factor that promote hair growth and regeneration are completely separate from suppressing the immune response. They stated that while using the skin tissue culture, they observed that glucocorticoids instruct the regulatory T cells to activate hair follicle stem cells, which leads to hair growth.

They explained that this crosstalk between the T cells and the stem cells depends on a mechanism where glucocorticoid receptors induce the production of the protein TGF-beta3. TGF-beta3, produced by the regulatory T cell, in turn, activates the hair follicle stem cells to differentiate into new hair follicles, promoting hair growth. 

(Source: https://timesofindia.indiatimes.com/videos/news/research-finds-link-between-immune-system-hair-growth/videoshow/96594700.cms )