Longitudinal egg-specific regulatory T and B cell development: insights from primary prevention clinical trials examining the timing of egg introduction.

BACKGROUND Egg allergy affects almost 1 in 10 Australian infants. Early egg introduction has been associated with a reduced risk in developing egg allergy, however the immune mechanisms underlying this protection remain unclear. OBJECTIVE To examine the role of regulatory immune cells in tolerance induction during early egg introduction. METHODS Cryopreserved peripheral blood mononuclear cells (PBMC) were obtained from infants from 2 randomized controlled trials of early introduction of egg for the primary prevention of egg allergy; BEAT (at 12 months, n = 42) and STEP (at 5 months n = 82; 12 months n = 82) study cohorts. In vitro ovalbumin stimulated PBMC were analyzed by flow cytometry for presence of ovalbumin-specific regulatory T cells, using activation markers, FoxP3 and IL-10 expression. Ovalbumin-specific regulatory B cells were identified by co-expression of fluorescence-conjugated ovalbumin and IL-10. RESULTS Specific, age dependent expansion of ovalbumin-specific regulatory T cells was only observed in infants who a) had early egg introduction and b) did not have egg allergy at 12 months. This expansion was blunted or impaired in children who did not undergo early egg introduction and in those with clinical egg allergy at 12 months. Infants with egg allergy at 12 months of age also had reduced frequency of ovalbumin-specific regulatory B cells compared to egg tolerant infants. CONCLUSION Early egg introduction and clinical tolerance to egg was associated with expansion of ovalbumin-specific T and B regulatory cells, which may be an important developmental process for tolerance acquisition to food allergens.