Auto-immune diseases are consider modern, industrial diseases.
The hygiene hypothesis and its analogues posit that divorcing humans from their natural parasites has left parts of the immune system without their natural complements.
This notion was first developed when Ethiopian Jews were relocated to Israel where they were dewormed. Before deworming, there were no incidences of auto-immune disease in this group; afterward, its members developed diseases/ conditions like IBD and asthma.
If this hyposthesis is to be believed, then it's no surprise that cases of IBD trend upward as countries become more modernized and more industrial.