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Immune cells help beneficial bacteria triumph over bad

By Tim Sandle     Apr 23, 2015 in Science
The immune system helps to shape the balance of good or bad bacteria in the human gut. Researchers have found a protein on white blood cells affects the balance of the microorganisms in the gut.
Studies on mice have shown a binding protein on white blood cells affects whether or not mice produce a balanced gut microbiota (a term for the different microbial species found within a niche). The researchers argue that without the protein, harmful bacteria can infect more easily. The cells containing the protein are termed type 3 innate lymphoid cells (ILC3s). The protein is Id2, which is not present on all cells.
To show the importance of this, researchers took bacteria from a mouse with dysfunctional ILC3s and transferred these into a completely germ-free mouse. Soon after, the recipient mouse became very susceptible to infections when exposed to pathogenic bacteria. In parallel studies, germ-free mice that received bacteria from mice with functional ILC3s could fight off the pathogens.
The inference from the research is that the immune system has a way to sense the presence of invading intestinal bacteria. Quite why and how this happens is uncertain.
The importance of the research, and for future studies, is in relation to antibiotic resistance. In a world where more strains of pathogenic organisms are becoming resistant to antibiotics, new ways to limit the harm that such pathogens can do — should they infect someone in high numbers — is important.
One strategy could be to inoculate a patient who is infected with a pathogen with beneficial bacteria in the hope that these additional organisms out-compete the pathogenic bacteria.
The research was carried out at the University of Chicago. The findings have been published in the journal Immunity. The paper is titled “Innate Lymphoid Cells Control Early Colonization Resistance against Intestinal Pathogens through ID2-Dependent Regulation of the Microbiota.”
More about Bacteria, Gut, Intestines, microbiome, Microbiota
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