The birth of immune tolerance

The immune system plays a vital role in our overall health: it is our bodies defence against infection and illness.

A 2015 study of young mice revealed that immune tolerance is established through exposure to healthy bacteria during infancy. The study showed that tolerance was built through a unique wave of active immune cells entering the skin during a critical window of time in early life – a response not observed on adult skin.[1]

This supports other studies that have considered over-sanitation early in life to be detrimental to normal development of the immune system, with evidence pointing at this lack of exposure to bacteria as a cause of allergies, asthma and other autoimmune disorders.

But what if we developed tolerance to harmful bacteria? This would pose a huge problem as the immune system would be unable to fight off an infection upon repeated exposure. A follow-up to the 2015 study investigated this possibility using a strain of Staphylococcus aureus, the leading cause of skin infections in the U.S.[2] Luckily, early life exposure to the bacteria did not result in tolerance; the immune system was still able to rapidly remove the infection upon later exposure to the same strain.

Further research into the early discrimination between healthy and harmful bacteria is needed to help better understand differences in susceptibility to infection. It would also inform new treatment strategies for skin disorders, such as chronic inflammatory skin diseases which appear to be exacerbated by the presence of normally tolerated bacteria.

References:

[1] https://www.sciencedirect.com/science/article/pii/S1074761315004410

[2] https://www.ucsf.edu/news/2019/11/416026/newborn-immune-system-detects-harmful-skin-bacteria

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