You can get this from the following foods, according to Wikipedia:
“FOS is extracted from the blue agave plant as well as fruits and vegetables such as bananas, onions, chicory root, garlic, asparagus, jícama, and leeks. Some grains and cereals, such as wheat and barley, also contain FOS. The Jerusalem artichoke and its relative yacón together with the blue agave plant have been found to have the highest concentrations of FOS of cultured plants.”
You can also buy it as a supplement, and may find it in some probiotic formulas and yogurts.
Oh, my, all of the antivaxxers out there better get on some strong antibiotics quickly and get rid of those gut bacteria ASAP.
After all, according to antivax rhetoric, initiating an immune response is one of the most dangerous things that your body can do. This must be avoided at all cost.
Seriously speaking, however, this seems like a mechanism for targeting immune responses to the gastrointestinal tract. I’m not certain that the gut bacteria secretions would have an effect on dendritic cell function elsewhere in the body.
Artichoke hearts are a good source of fiber.