Eating this Fatty Acid Helps Immune Cells in the Gut

Researchers say one specific fatty acid plays a crucial role in building the immune system in the gut microbiome.

In a new study published on June 28 in Nature, scientists from Harvard Medical School discovered how food choices might impact a specific type of immune system residing in the gastrointestinal tract.

The research, done in mice, found that linoleic acid — a polyunsaturated essential fatty acid found mainly in plant oils — interacts with gut microbes to produce a byproduct that boosts the development of immune cells known as CD4+CD8aa+ intraepithelial lymphocytes (IELs) in a specific part of the small intestine.

In the study's first phase, the scientists observed that mice modeled to have no gut microbiome — also known as germ-free mice — had no CD4+CD8aa+ IELs immune cells in their small intestines.

In addition, the researchers noticed that in mice with a typical microbiome, those who consumed a minimal diet also lacked these immune cells. However, those eating a nutrient-rich diet had CD4+CD8aa+ IELs cells in their small intestines.

These observations piqued the team's interest. So, they investigated further by examining the rodent's minimal diet to determine which nutrients were lacking.

Eventually, the team focused on various fatty acids and proceeded to feed specific types to the mice eating a minimal diet.

The researchers discovered that when they fed these mice linoleic acid — a common fatty acid — the rodents began to develop CD4+CD8aa+ IELs in their small intestines.

Further investigations revealed that gut microbes consume linoleic acid and convert it into conjugated linoleic acid (CLA). CLA then signals a biological process that initiates the development of CD4+CD8aa+ IEL.

What’s more, disrupting this process negatively impacts the immune response. Specifically, researchers found that mice who didn't produce CD4+CD8aa+ IELs were more likely to die when infected with Salmonella typhimurium — a bacterial species responsible for food poisoning.

However, because the researchers used mice in their investigations, it's unknown how this intricate process occurs in humans. Still, the study authors say that researching these pathways will help scientists better understand the gut microbiome's role in immune system function and hopefully reveal new strategies to boost gut health.

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