Human cells are outnumbered ten-to-one by the microbes that thrive in and on us. Now a study finds that the tiny organisms living in our lungs may protect us from asthma.

A newborn’s lungs start out sterile and then become colonized by microbes. To see how lung microbes might influence disease susceptibility, researchers studied mice, which also start with sterile lungs that soon host microbes.

In the first two weeks of life, these microbial communities shift and proliferate. So the scientists looked at three groups of mice: babies three days old, 15-day-old mice, and two-month old adults. All were exposed to dust mites, which provoke inflammation.

The newborn mice developed inflamed lungs—similar to asthma. But the older groups remained mostly inflammation free, indicating a protective role for their lung microbes.

The researchers then exposed older mice whose lungs had been kept sterile to mites. These mice did get inflamed lungs. The study is in the journal Nature Medicine. [Eva S. Gollwitzer et al, Lung microbiota promotes tolerance to allergens in neonates via PD-L1]

The researchers say that early lung colonization by a diverse, protective microbial community appears crucial. They hope to extend these studies to human infants—to better understand our lung microbes, and help kids breathing freely. (Also see Drugs to Be Derived from Insights into Body-Dwelling Bacteria)

—Cynthia Graber

[The above text is a transcript of this podcast.]

[Scientific American is part of Nature Publishing Group.]