Unravelling the striking effects of our skin microbes

By Meaghan Lee-Erlandsen and Dr. Nora Khaldi

We at Nuritas™ recently came across a very intriguing article published in Nature that explains how skin microbes trigger specific immune responses. The effects of the microbial community on our skin cells in terms of interaction or influence is still unknown, and thus this paper was of great interest to us. We decided to reach out to Dr. Yasmine Belkaid, one of the lead authors on this publication for further details on this groundbreaking work. Dr. Belkaid and her co-authors are based in the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institute of Health.

Dr. Belkaid, could you summarize your findings for us? “Our research in mice shows that the immune system in the skin develops distinct responses to the various microbes that naturally colonize the skin, referred to as commensals. My co-authors and I found that each type of microbe triggers unique aspects of the immune system, suggesting that immune cells found in the skin can rapidly sense and respond to changes in microbial communities. These findings help clarify the protective role of skin commensals and may help explain how variation in the microbes at different skin sites contributes to skin disorders.”

Dr. Belkaid continues: “The skin is home to diverse microbial communities that can change over time. In the current study, we found that colonizing mice with different commensals leads to production of commensal-specific immune cells. We describe in detail how the common skin commensal Staphylococcus epidermidis enhances immune responses against pathogens without causing inflammation.”

So it seems that skin bacteria, such as Staphylococcus epidermidis, could exercise protective effects on the skin, could you explain the science behind this in a little more detail? “Colonizing the skin of mice with S. epidermidis increased the number of CD8+ T immune cells, which produced the chemical messenger IL-17A. Dendritic cells, another type of immune cell, played a key role in generating this specific, non-inflammatory response. Mice colonized with S. epidermidis were protected against infection with a disease-causing fungus. Depleting CD8+ T cells or neutralizing IL-17A removed this protective effect.”

How do you see your findings being applied in the future? “The ability of different microbes to trigger distinct aspects of the immune system without causing inflammation opens the possibility of discovering new adjuvants—immune-boosting substances that may be added to vaccines or medications. Future research will focus on identifying specific chemical messengers and understanding how they stimulate the immune system.”

The interaction between bacteria and the human host is an intricate business. We have trillions of bacteria living on our skin, and yet to this day we have a limited understanding of our relationship with these visitors populating our skin’s surface! Recent research, including that of Dr. Belkaid and her co-authors, shows that the interaction of the skin’s commensal bacteria with our bodies can have a far greater influence than we had previously anticipated. Understanding the mechanisms by which these bacteria communicate with our human cells, with each other, and their interaction with topical creams, soaps and chemicals so commonly applied on our skin would be a great step forward.

As our understanding of this relationship develops one could imagine the potential of developing skincare applications to promote the growth of specific bacteria to improve specific skin conditions. This type of research is certainly helping pave the way.

References:
• Naik S, Bouladoux N, et al. Commensal–dendritic-cell interaction specifies a unique protective skin immune signature. Nature 520, 104–108 (02 April 2015) doi:10.1038/nature14052