Bringing this to the article, the authors are outside that consensus. They believe that Crohn's is an immune response directed toward a bacterium, rather than t

Bringing this to the article, the authors are outside that consensus. They believe that Crohn's is an immune response directed toward a bacterium, rather than toward the self. The hypothesis in the paper is that Crohn's isn't autoimmunity and that improving hygiene might prevent or treat it. Edit: They do mention a training set factor, but at the level of population genetics instead of at the level of an individual developing immune system. Their evidence is that a history of the plague, rather than hygiene, promoted a genetic immune system weakness that made people more likely to survive the plague, but that Crohn's is a consequence of that today. A related example that comes to mind is the prevalence of sickle cell anemia in regions with malaria.