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GEN News Highlights : Oct 30, 2013
Immune System Helps Dictate Microbes Found on Human Skin
Scientists at the National Cancer Institute (NCI) have published a study online in Genome Research that sheds light on how the immune system influences the types of microbes that live on the skin and thus potentially prevents disease. Their work was partially based on previous research, which examined such microbes on the skin of patients with primary immunodeficiencies with eczema-like skin conditions.
“In addition to questions about how microbes affect the human host, there is an interest in understanding how the human host affects the microbes that make our skin their home,” said Heidi Kong, Ph.D., of the NCI and co-senior author of the study (“The altered landscape of the human skin microbiome in patients with primary immunodeficiencies”).
To study this, the authors enlisted patients with reduced immune function as a result of rare genetic defects. Despite the diversity in disease-causing mutations in the patients, all patients shared an eczema-like skin condition.
“To investigate the potential influence of host immunity on the skin microbiome, we examined skin microbiomes in patients with rare monogenic PIDs [primary immunodeficiencies]: hyper-IgE (STAT3-deficient), Wiskott-Aldrich, and dedicator of cytokinesis 8 syndromes,” wrote the investigators in the journal article. “While specific immunologic defects differ, a shared hallmark is atopic dermatitis (AD)–like eczema. We compared bacterial and fungal skin microbiomes at four clinically relevant sites representing the major skin microenvironments. PID skin displayed increased ecological permissiveness with altered population structures, decreased site specificity and temporal stability, and colonization with microbial species not observed in controls, including Clostridium species and Serratia marcescens.”
Because these immunodeficient patients had types of bacteria and fungi on their skin not found on healthy individuals, this indicated that the patients’ skin was more permissive to microbe growth.
“Our findings suggest that the human body, including our immune systems, constrains and potentially selects which bacteria and fungi can inhabit skin,” said Dr. Kong.
The skin sites specifically prone to disease showed significant differences in microbial diversity in immundeficient patients. The skin at the elbow crease, for instance, had fewer types of microbes than found on healthy individuals, while skin behind the ear had more types of microbes. The authors believe that an imbalance in microbial diversity at a given site may contribute to disease.
In addition, “the communities of bacteria and fungi on the skin of primary immunodeficiency patients are more likely to change over time,” said co-senior author Julie Segre, Ph.D., of the National Human Genome Research Institute (NHGRI).
Although the individuals in this study have rare genetic disorders, this research may have implications for patients with temporary impairments in immune function, such as cancer patients and transplant recipients, and may inform the use of preventative antibiotics that are routinely given to these patients, noted the researchers.
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