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
Blood Will Tell
One common tool for studying neonatal immune responses is blood taken from the umbilical cord at birth. The blood cells are from the baby rather than the mother, and such cord blood mononuclear cells, or CBMCs, can be studied in culture as a proxy for the fetal immune system.
We wanted to examine how exposure to LPS from bacteria during early antigen encounters might influence the responsiveness of neonatal T and B cells, including the activation of Treg cells by a food antigen. We also wondered whether it would be possible to use this measure to distinguish neonates with a high risk of allergy (because of family history) from controls with no hereditary risk. In fact, the stimulation with cow's-milk protein did cause greater (less controlled) proliferation of CBMCs from infants predisposed to atopy, suggesting that this test might predict later allergies. Various subsets of T cells, as determined by their immunological cell-surface markers, were also distinct between groups. After stimulation with a combination of milk antigen and LPS, the cells from babies with a family history of atopy expressed less of the markers overall, a trait that implied delayed development of a balanced immune system. The induction of Treg cells was also significantly impaired.
These data support the idea that induction of immunity should normally be modulated very early in life under the influence of genes and microbes. However, the CBMC model can only reveal small pieces of the mechanistic puzzle. Immunological events in the gut are much more complex, and mucosal homeostasis probably involves a multitude of processes.
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