| Health / Health News |
Infant gut microbes linked to allergy, asthma risk
Our digestive tracts are home to trillions of microbes—including bacteria, fungi, and viruses. This microbial community, known as the microbiota, plays a role in illness and health.
Escherichia coli, one of the many species of bacteria present in the human gut. 
Scientists have suspected that infants’ gut microbiota could influence how their immune systems develop. A team from the Henry Ford Health System in Detroit and from the University of California, San Francisco, set out to examine the relationship between an infant’s gut microbiota and subsequent development of allergy and asthma.
To determine the composition of gut microbes in the stool samples, the scientists examined sequence variation within ribosomal RNA (rRNA), a central component of the protein-manufacturing machinery of all living cells. The investigators found that the infants formed 3 groups characterized by distinct bacterial and fungal gut microbiota.
Blood samples obtained from the infants at 2 years of age were tested for sensitivity to allergens. The researchers found that the 3 microbiota groups had substantially different risks for allergen sensitivity.
The “high-risk” group had a relatively lower abundance of certain bacteria (such as Bifidobacterium, Akkermansia, and Faecalibacterium) and a higher level of some fungi (such as Candida and Rhodotorula). This high-risk microbiota group was also more likely to be diagnosed with asthma at 4 years of age.
The relationship between gut microbiota and allergy and asthma held when the researchers controlled for other factors associated with allergic disease, such as breast feeding and dog allergens in the home.
The team analyzed metabolites in some of the infant’s stool samples. They found extensive differences among the 3 groups. Notably, the high-risk group had greater levels of metabolites that promote inflammation.
The scientists next exposed immune cells from healthy adults to metabolites extracted from the infant’s stool samples.
The high-risk group’s samples increased the proportion of allergy-promoting immune cells and production of interleukin-4, an allergy-associated cell-signaling protein. These samples also reduced T-regulatory cells, a key group of immune cells necessary to prevent allergic responses.
The team identified a lipid found at high levels in the highest risk group, called 12,13-DiHOME, that could suppress T-regulatory cells. It seems that the microbial communities within the body could be the keystone to understanding this and a number of different immune diseases. (NIH)
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