Could newborns’ blood predict their food allergies?

Why is it that some kids can scarf peanuts by the handful, but a single nut can cause serious problems for others? A new study might be closer to answering this, as research shows kids who develop food allergies already have blood rich in cells that promote a hyperactive immune response when they are born.

Researchers led by Yuxia Zhang, an immunologist at the Walter and Eliza Hall Institute of Medical Research in Australia, studied more than 1,000 newborns and took blood from the children's umbilical cords to profile the immune cells and molecules floating within.

The children were then tested for food allergies in a range of foods, including eggs, cow’s milk, and peanuts, a year later.

By sampling the baby’s blood from the umbilical cord, researchers were able to get an early snapshot of the child’s immune system. They’ve found that blood from kids who later developed food allergies contained more chemical signals that promote inflammation and lower-than-normal concentrations of natural regulatory T cells, which tone down immune system responses.

Based on these tests, the team was able to pinpoint a type of immune cell called a monocyte, whose numbers were higher in the cord blood of kids who went on to develop food allergies. Monocytes transform into pathogen-fighting cells when they encounter an invader. In lab tests, the monocytes of children who developed allergies transformed more readily (were more eager to fight) than the monocytes from kids without allergies.

"Normally, a strong response is good; it means the immune cells are ready to fight bacteria and viruses,” the research team wrote. But in food-allergic kids, the researchers added that they suspect that such overactive monocytes could keep the immune system in a state of high alert, signaling more immune cells to transform and the immune system to react. As a result, these eager-to-fight monocytes provoke a cascade of different molecules and cells to react to normally harmless things like a peanut protein.

Even so, the result found in the study are not ironclad. "There are some babies with the signature that don't develop food allergies, which suggests other factors come into play in the first year of life," Lee Harrison, an immunologist on the research team, said in the article.

Immune systems are so complex, and together with the variety of factors that influence pregnancy and a child's development, this is only the beginning. While the researchers explain that these results are promising, they likely offer only part of the overall picture.

Genes, the mother's diet, the baby's exposure to food and other factors all might also play into the development of allergies. Understanding all those factors and how they work together will be necessary in finding any way to prevent food allergies in the future, the researchers said.

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