IKZF2 and allergic disease: While there was no correlation between the Helios MFI and total Treg in any of the groups (Supplementary Figure S8a–c), unsurprisingly, a strongly significant negative correlation was found between the Helios MFI and iTreg when data were analyzed regardless of maternal allergy status and newborns’ sex (Figure 4d, r = −0.3833, p < 0.0001).