Researchers have discovered that friendly bacteria not only help in digestion, but also fight against the flu.
Akiko Iwasaki, an immunologist at Yale University, and her colleagues treated mice with neomycin antibiotics and found that it were more prone to influenza viruses, reports Nature.
The antibiotic-sensitive bacteria naturally present in the mice's bodies provided a trigger, leading to the production of T cells and antibodies that could fight a flu infection in the lungs.
The researchers found that the bacteria activated 'inflammasome' protein complexes in the immune system, which then activated precursors of an immune protein - the cytokine interleukin 1-beta.
Mature interleukin 1-beta triggered dendritic immune cells to migrate to lymph nodes in the lungs, where they initiate a potent attack on influenza viruses.
They found that when antibiotics eliminated the bacteria, inflammasomes failed to launch and the virus multiplied.
Previous researches have found that helpful microbial interactions don't stop at the gut, but Iwasaki's study is the first to identify how bacteria fight infections in the lungs.
"This study contributes to a growing body of literature showing that signals from commensal bacteria can have an impact on immune cells in multiple tissues," said David Artis, an immunologist at the University of Pennsylvania in Philadelphia.
"If certain antibiotics have an effect on our ability to mount a response against a viral infection, it means that people should be careful to only take antibiotics when they are absolutely needed - particularly in the flu season," he said.
"In addition, the findings suggest that our diet might affect our ability to fight viruses by influencing the composition of our commensal bacteria," he added.
Iwasaki, however, has cautioned that her team had not identified the bacteria responsible for the immune response.
The study is published in the Proceedings of the National Academy of Sciences.