Egg-sensitised infants have elevated CD4 effector memory T regulatory cells from birth.

Background: IgE-mediated sensitisation to egg is common in infants. In some cases, the processes leading to egg sensitisation are established in early life, even before introduction to solid foods. The underlying mechanisms remain poorly understood.

Methods: We performed detailed immune cell phenotyping of peripheral blood mononuclear cells and determined in vitro cytokine responses following allergen specific and non-specific immune stimulation. To determine if unique immune profiles were linked to early-life egg sensitisation, we compared 92 infants at 4-6 months of age, with (EggCAP+, n = 41) and without (EggCAP-, n = 51) early egg sensitisation. Additionally, 47 cord blood samples were analysed. For a subset of participants (n = 39), matching cord blood mononuclear cells were assessed by flow cytometry to establish the impact of IgE sensitisation on immune developmental trajectories.

Results: EggCAP+ infants were found to exhibit a unique immune phenotype characterised by increased levels of circulating CD4 T regulatory cells (Treg), CD4 effector memory (EM) Treg and increased expression of the IgE receptor, FcεR1, on basophils. The increased CD4 EM Treg profiles were already present in cord blood samples from EggCAP+ infants. A general Th2-skewing of the immune system was observed based on increased IL-13 production following phytohemagglutinin stimulation and by comparing immune developmental trajectories, EggCAP+ infants displayed an expansion of basophils and reduced levels of CD4 T cells compared to EggCAP- infants.

Conclusions: Immunological profiles associated with egg sensitisation are detectable in infant circulation at 4-6 months of age and at birth. Understanding the immune mechanisms underlying early-life sensitisation could provide important insights for future food allergy prevention strategies.