The skin has long been thought of as a mere physical barrier to attack by pathogens. Now, however, researchers are starting to realize that this simplistic view needs a radical rethink.
The folds, follicles and tiny oil-producing glands on the skin’s surface create a multitude of diverse habitats, each with its own community of microbes1. Most of these ‘commensals’ live harmlessly on the skin, and their presence is thought to stop pathogenic microbes from invading the skin’s habitats. But these benign residents are not just innocent bystanders — according to a paper published today in Science, skin-specific bacteria also influence the response from the host’s immune system to help fight off infection2.
Immunologist Yasmine Belkaid and her team at the National Institute of Allergy and Infectious Diseases in Bethesda, Maryland, decided to investigate the immunological role of the skin’s resident microorganisms, known collectively as the skin microbiome. “For the first time, we’ve shown that the skin needs microbial signals for proper immune-cell function,” says study author Shruti Naik, a graduate student at the University of Pennsylvania, Philadelphia, who is based in Belkaid’s lab.
Most studies of how resident microorganisms regulate the immune system and inflammation have focused on the gut microbiome, largely because it is the site of greatest exposure and contains a wide diversity of microbes. But Belkaid and her colleagues wanted to determine whether the skin microbiome performed a similar function.
“No one had any idea of the relative magnitude of the immunological effect in skin, or how similar any mechanisms found outside the gut would be to those occurring inside the gut,” says Curtis Huttenhower, a computational biologist at the Harvard School of Public Health in Boston, Massachusetts, who is involved in the Human Microbiome Project. “This paper is the first good demonstration I’ve seen that shows the skin microbiome has a parallel immunological response to that seen in the gut.” Via The skin’s secret surveillance system