A recent study on immune cells has accidentally unveiled a major element that contributes to some conditions that cause hair loss.

According to Medical Daily, the original purpose of the study conducted at the University of California at San Francisco was to investigate the relationship between skin health and regulatory T cells, commonly known as “Tregs.”

This type of immune cell is typically associated with inflammation and helping the body to differentiate the harmless from the harmful. Defective Tregs are involved in several diseases in which the immune system attacks something that should be harmless, such as one’s own tissue or a certain protein.

Researchers began the study by removing Tregs from patches of skin in order to observe what this would do to the immune system. What they did not expect to see, however, was the effect this process had on hair growth.

Prior to the removal of the Tregs, hair had been shaved off the patches of skin used in the study. The team found that once the Tregs were removed, the hair on these patches of skin did not grow back.

Before this discovery, the scientific community was under the impression that stem cells were entirely responsible for the regrowth of hair. But the new research shows that stem cells are only able to regenerate hair follicles with the help of Tregs.

“Our hair follicles are constantly recycling: when a hair falls out, the whole hair follicle has to grow back,” senior study author and professor Michael Rosenblum said in a statement. “This has been thought to be an entirely stem cell-dependent process, but it turns out Tregs are essential. If you knock out this one immune cell type, hair just doesn’t grow.”

The discovery prompted the team to further investigate a potential connection between Tregs and alopecia areata, an immune disorder in which the immune system attacks hair follicles, causing hair to fall out.

An examination of the genes associated with alopecia areata revealed that almost all of them are related to Tregs. This makes sense considering previous research has reportedly shown that treatments designed to improve Treg functionality can be used to treat alopecia areata as well. Defects in Tregs could therefore be a significant contributor to alopecia areata as well as other conditions that cause hair loss.

The findings also support the theory that Tregs co-evolved with stem cells and assist the regenerative properties of stem cells while protecting them from inflammation.

"We think of immune cells as coming into a tissue to fight infection, while stem cells are there to regenerate the tissue after it's damaged. But what we found here is that stem cells and immune cells have to work together to make regeneration possible,” Professor Rosenblum added.

It seems that stem cells will only begin the hair regrowth process when Tregs direct them to do so.

The team plans on conducting further studies on Tregs that could lead to the development of more effective hair loss treatments. Such studies might also seek to confirm whether or not alopecia areata can be chalked up to defective Tregs.