FEATURE ARTICLE
Why We Develop Food Allergies
Coached by breast milk and good bacteria, the immune system strives to learn the difference between food and pathogens before the first morsel crosses our lips
Per Brandtzaeg
Milk Model
Four out of five children who are allergic to cow's milk outgrow the problem before school age, which makes this disorder a good model for exploring the complexities of oral tolerance. Experiments in mice suggest that oral tolerance is brought about mainly by the actions of CD25+ Treg cells, although other mechanisms may also be involved.
In a recent study, our research team at the University of Oslo looked at a group of children who were all initially allergic to cow's milk. After a two-month dairy-free period, we gave the children cow's milk for up to one week. The challenged kids who then had outgrown the allergy (13 of 21) showed numerically more, and functionally better, Treg cells in peripheral blood than did children who remained allergic. And when we studied effector T cells from the children in vitro, those from the first group did not react as strongly to cow's-milk protein as did cells taken from children whose allergy persisted. However, in the same blood samples, removing the CD25+ cells (including Treg cells) caused a five-fold increase in the immune response to milk protein, which suggested to us that this subset of T cells had contributed to the developed tolerance to cow's-milk antigens.
Our study provided the first human data that link the induction of oral tolerance to the development of CD25+ Treg cells. This insight could prove useful as a diagnostic tool, and Treg cells might someday be candidates for preventing or treating allergy.
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