Anyone who has weathered a bad stomach bug knows the feeling: a loss of appetite that sets in and lingers, even after the initial illness. For the millions of people around the world who are chronically infected with parasitic worms, the same thing happens. But scientists have long puzzled over exactly why. Researchers at UC San Francisco now report that they have traced the molecular pathway that connects the gut immune system to the brain during a parasitic infection, explaining how the immune system triggers a loss of appetite. The findings reveal an unexpected communication system between two cell types, tuft cells and serotonergic enterochromaffin cells (ECs), and could shed light on a range of conditions involving gut discomfort—from food intolerances to irritable bowel syndrome. “The question we wanted to answer was not just how the immune system fights parasites, but how it recruits the nervous system to change behavior,” said co-senior author David Julius, PhD, professor and chair of Physiology at UCSF and recipient of the 2021 Nobel Prize in Physiology or Medicine. “It turns out there’s a very elegant molecular logic to how that happens.” Julius is senior author of the researchers’ published paper in Nature, titled “Parasites trigger epithelial cell crosstalk to drive gut–brain signaling,” in which they concluded, “Our investigation of paracrine communication between tuft and EC cells now reveals a direct link between sensory and immune systems that alters food intake through the gut–brain axis.” The UCSF researchers worked in collaboration with Stuart Brierly, PhD, and…
