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An Atlas for Immune Cells in Skin

Researchers at the Centenary Institute have developed the first 3D model of the distribution of immune cells in living mammalian skin.

“It takes us from something like a paper map to Google Street View,” says the study’s lead author, Dr Philip Tong. “We knew all of these cells were there, but not how many of them and where. Now we can dive right in and we see that some types of immune cells are evenly distributed while others clump in strategic locations.”

The resulting “Atlas”, posted online by the Journal of Investigative Dermatology, provides the basis for understanding an immune response at a particular site of the skin. It helps explain why injecting the same vaccine or drug to different areas of the skin can generate a different immune response.

The study found that some immune cells in the skin of mice, such as the infection-detecting dendritic cells, are evenly distributed throughout the skin while others, such as the inflammatory mast cells, only occur at certain depths or regions where they can have most impact – in this case close to blood vessels. In mice there were more T cells in the skin on the back than in the other areas.

Furthermore, the proportions of different types of immune cells changed over time. For instance, in older mice there were greater numbers of the first-strike gamma-delta T cells. Likewise older mice had more alpha-beta T cells, which contain the cells that recognise past infections.

While the study was not geared to interpret human disease, it should allow a better understanding of what goes on in the mouse models used to study disease mechanisms. “This is a baseline study. But it has wide implications for any study involving the immune response of skin,” Tong says.

The work could also open the way to similar maps of the human immune system, allowing finer diagnosis and better targeted-treatments for skin infections.

The next step will be to expand the work to human skin, and also to incorporate further features such as nerves and the lymphatic system.