Paventa Rajni

The study compared blood samples from urban infants with those from infants in a farming community, specifically the Old Order Mennonites (OOM) of New York's Finger Lakes region--known for their low rates of allergies. Researchers found that while urban infants had higher levels of the aggressive Th2 cells, OOM infants had more regulatory T cells that help keep the immune system in balance and reduce the likelihood of allergic responses.

While additional research is needed to identify a possible cause, Jarvinen-Seppo speculates that differences in the development of the gut microbiome between the two populations, and more exposure to "healthy" bacteria in rural children, may be a factor.

"The farming environment, which is rich in microbial exposure, appears to support the development of a more tolerant immune system. Meanwhile, the urban environment may promote the emergence of immune cells that are primed for allergic inflammation," said Jarvinen-Seppo.