Dirty living good for the immune system

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A study published in BMC Biology provides a direct link between dirty living, immune health, and gene expression.

Researchers studied the gut bacteria of piglets raised under three different conditions. The first group of piglets was raised in an outdoor environment, the second in an indoor environment, and the third in an isolated indoor environment where they were fed antiobiotics every day.

They found that 90% of the gut bacteria was from the Firmicutes phylum in the outdoor piglets, compared to 70% in the indoor piglets, and 50% in the piglets fed antibiotics. Most of the bacteria was lactobacillaceae, known for its health benefits and ability to limit pathogens like Escherichia coli and Salmonella. The indoor piglets and piglets fed antiobiotics also a lower percentage of "good bacteria".

The gut bacteria population was also shown to influence gene expression. The piglets fed antiobiotics expressed more genes associated with cholesterol synthesis and inflammatory immune response whereas the dirty outdoor pigs showed more gene expression associated with T-cells, a type of lymphocyte that play a central role in cell-mediated immunity.

The gut bacteria and organ size are similar between pigs and humans, but there is no guarantee that these results will be applicable to humans, although it seems likely. [Nature]