Cells involved in the first line of our immune defence have been located where they never have been found before—a discovery that could provide insight into diseases like psoriasis and other auto-immune conditions of the skin.

While researchers have known about these cells, called gamma delta T cells in the epidermis or top layer of skin for more than 20 years, this is the first time their presence has been detected in the next layer of skin down, the dermis.

Wolfgang Weninger, who led the study at Sydney’s Centenary Institute, says that gamma delta T cells are of particular interest because they produce a protein thought to be the ‘first responder’ when intruders are detected by the immune system.

“Interleukin-17 is a cytokine that has been getting a lot of interest because of its role in inflammation,” Wolfgang says.

The researchers used mycobacteria—related to the bacteria which cause tuberculosis—to investigate the defence mechanisms of these immune cells in the dermis. When exposed to mycobacteria the gamma delta T cells in the dermis produced Interleukin-17, while their better known counterparts in the epidermis did not contribute to immune defence.

“This supports the notion that related immune cells have specialist and unique functions in each layer of the skin. The likely reason for this is that different microbes tend to infect different skin layers. For example, herpes viruses infect the epidermis while bacteria tend to invade the dermis and deeper layers of the skin,” Wolfgang says.

Photo: A stain showing the presence of gamma delta T cells (green) in the dermis. The blood vasculature is shown in red, while blue represent collagen.

Credit: Centenary Institute

Centenary Institute, Wolfgang Weninger, w.weninger@centenary.org.au, www.centenary.org.au