The researchers believe biological and environmental factors in pregnancy, such as labour, infections, diet, or gut microbes, trigger these cells to become “hyperactive” in some, causing an allergic response.
Cord blood samples from more than 1000 babies from the Barwon region were analysed, and the babies tested for food allergies at age 12 months.
The study found babies at high risk of food allergies had immune systems that, by birth, were already “primed” for allergic disease, having been stimulated by some infection or inflammation.
A chain reaction was set off between different layers of immune cells, and certain specialised immune cells were transformed into cell types that initiated an allergic response.
Co-lead author Professor Len Harrison, of the Walter and Eliza Hall Institute, said the study highlighted the value of early, even pre-birth, research on how the immune system set the stage for allergies and auto-immune illness.
“It was a surprising and exciting finding. The children who develop allergies, they all have the signature,” he said.
“It appears other factors may need to appear in the first day of life that add to this priming effect. The activation of these cells could be genetic, but more likely it’s exposure to something during pregnancy.”
The team will now look at pregnant women’s lifestyles and biology to try to pinpoint food allergy risk factors, so as to recommend an optimum lifestyle for pregnant women.
“We’re thinking nutraceutical foods, not smoking, making sure vitamin D is adequate, trying to avoid antibiotics, and looking at microbiomes in the gut,” Prof Harrison said.