Naïve regulatory T cells in infancy: Associations with perinatal factors and development of food allergy

Background In previous studies, deficits in regulatory T‐cell (Treg) number and function at birth have been linked with subsequent allergic disease. However, longitudinal studies that account for relevant perinatal factors are required. The aim of this study was to investigate the relationship between perinatal factors, naïve Treg (nTreg) over the first postnatal year and development of food allergy. Methods In a birth cohort (n = 1074), the proportion of nTreg in the CD4+ T‐cell compartment was measured by flow cytometry at birth (n = 463), 6 (n = 600) and 12 (n = 675) months. IgE‐mediated food allergy was determined by food challenge at 1 year. Associations between perinatal factors (gestation, labour, sex, birth size), nTreg at each time point and food allergy at 1 year were examined by linear regression. Results A higher proportion of nTreg at birth, larger birth size and male sex was each associated with higher nTreg in infancy. Exposure to labour, as compared to delivery by prelabour Caesarean section, was associated with a transient decrease nTreg. Infants that developed food allergy had decreased nTreg at birth, and the labour‐associated decrease in nTreg at birth was more evident among infants with subsequent food allergy. Mode of birth was not associated with risk of food allergy, and there was no evidence that nTreg at either 6 or 12 months were related to food allergy. Conclusion The proportion of nTreg at birth is a major determinant of the proportion present throughout infancy, highlighting the importance of prenatal immune development. Exposure to the inflammatory stimulus of labour appears to reveal differences in immune function among infants at risk of food allergy. Exposure to labour was associated with a marked decrease in naïve regulatory T cells (nTreg) at birth, which was transient. This decrease in nTreg at birth was more evident among infants with subsequent food allergy. Exposure to labour itself was not a risk factor for subsequent food allergy. Gender, larger birth size and higher proportion of nTreg at birth were each associated with higher numbers of nTreg in infancy.