According to new research from scientists at the National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health,  Beneficial bacteria on the skin of lab mice work with the animals' immune systems to defend against disease-causing microbes and accelerate wound healing . The study findings were published in the  Cell .

Mammalian barrier surfaces are constitutively colonized by numerous microorganisms. Researchers explored how the microbiota was sensed by the immune system and the defining properties of such responses. Here, they showed that a skin commensal can induces T cell responses in a manner that is restricted to non-classical MHC class I molecules.

Researchers said untangling similar mechanisms in humans may improve approaches to managing skin wounds and treating other damaged tissues. Like humans and other mammals, mice are inhabited by large, diverse microbial populations collectively called the microbiomeWhile the microbiome is believed to have many beneficial functions across several organ systems, little is known about how the immune system responds to these harmless bacteria.

To investigate, The National Institute of Allergy and Infectious Diseases ( NIAID ) led by Yasmine Belkaid, chief of the Mucosal Immunology Section of NIAID's Laboratory of Parasitic Diseases, observed the reaction of mouse immune cells to  Staphylococcus epidermidis , a bacterium usually found on human skin that does not normally cause disease.

To their surprise, immune cells recognized  S. epidermidis  using evolutionarily ancient molecules called non-classical MHC molecules, which led to the production of unusual T cells with genes associated with tissue healing and antimicrobial defense. In contrast, immune cells recognize disease-causing bacteria with MHC molecules, which leads to the production of T cells that stoke inflammation.

Researchers then took skin biopsies from two groups of mice – one group that had been colonized by  S. epidermidis  and another that had not. Over five days, the group that had been exposed to the beneficial bacterium experienced more tissue repair at the wound site and less evidence of inflammation.

Dr. Belkaid's team plans to next probe if non-classical MHC molecules recognize friendly microbes on the skin of other mammals, including humans, and similarly benefit tissue repair. Eventually, mimicking the processes initiated by the microbiome may allow clinicians to accelerate wound healing and prevent dangerous infections , the note.