eLife Assessment
IL-10 balances protective and deleterious immune functions in mice and humans, but if IL-10 also controls avian intestinal homeostasis remains unclear. Generating genetic knockouts, Meunier et al. established that a complete lack of IL-10 strengthened immunity against enteric bacteria in chickens, while also aggravating infection-inflicted inflammatory tissue damage and dysbiosis upon parasite infection, but unlike mouse models, IL-10 deficiency did not provoke spontaneous colitis in chickens. The findings presented are valuable, and the strength of evidence is convincing. The observation may have implications for the livestock industry and additional studies involving genetic knockouts may further unravel conserved and distinct avian IL-10 controls.