Source: Medical Xpress

The human body is inhabited by billions of symbiotic bacteria, carrying a diversity that is unique to each individual. The microbiota is involved in many mechanisms, including digestion, vitamin synthesis and host defense. It is well established that a loss of bacterial symbionts promotes the development of allergies. Scientists at Helmholtz Zentrum Munich, at the Technical University of Munich (TUM), and Institut Pasteur in Paris have succeeded in explaining this phenomenon, and demonstrate how the microbiota acts on the balance of the immune system: the presence of microbes specifically blocks the immune cells responsible for triggering allergies. These results are published in the journal Science.

The hygiene hypothesis suggests a link between the decline in infectious diseases and the increase in allergic diseases in industrialized countries. Improvements in hygiene levels necessarily lead to reduced contact with microbes that is paralleled by an increased incidence in allergic and autoimmune diseases, such as type 1 diabetes. Epidemiological studies have substantiated this hypothesis, by showing that children living in contact with farm animals – and therefore with more microbial agents – develop fewer allergies during their lifetime. Conversely, experimental studies have shown that administering antibiotics to mice within the first days of life results in a loss of microbiota, and subsequently, in an increased incidence in allergy. However, until now, the biological mechanisms underlying this phenomenon remained unclear.

Microbiota is essential for preventing allergies

In this study published in Science, the team around Dr. Caspar Ohnmacht at Center of Allergy and Environment (ZAUM) of Technical University of Munich and Helmholtz Zentrum Munich and around Gérard Eberl, head of the Microenvironment and Immunity Unit at the Institut Pasteur, shows that, in mice, symbiotic intestinal microbes act on the immune system by blocking allergic reactions. Several types of immune response can be generated in order to defend the organism. The presence of bacterial or fungal microbes provokes a response from immune cells known as type 3 cells. These immune cells coordinate the phagocytosis and killing of the microbes… Read More>>

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