Elevated Specific IgE to Bystander Foods in Children with Peanut Allergy

Circulating food-specific IgE (sIgE) levels are associated with the development of allergic responses. However, food-specific IgG4 (sIgG4) levels have been associated with tolerance or clinical non-responsiveness, particularly in interventional studies. We aimed to characterize food-specific antibody responses in a more general pediatric food allergy population. We measured serum specific IgA (sIgA), sIgG4, and sIgE to whole peanut, egg white, and wheat, along with total IgE, from 46 children (20 with peanut +/- egg allergy, 6 with natural tolerance, and 20 without any history of food allergy by Phadia ImmunoCAP. sIgE and sIgG4 levels to peanut were highest in children with peanut allergy compared to naturally tolerant or control children (p<0.002, p<0.001 respectively). However, the specific IgG4/IgE ratio was lower in children with food allergies compared to control and naturally tolerant children (p<0.001). Interestingly, children with only peanut allergy had comparable egg sIgE and wheat sIgE levels to children with both peanut and egg or peanut and wheat allergy. Children with only peanut allergy also had higher levels of egg and wheat sIgE compared to naturally tolerant or control children (p<0.02, p<0.01 respectively). sIgA levels were undetectable in 89% of participants, and total IgE was highest in children with food allergy compared to children without food allergy or natural tolerance (p<0.001). Our findings indicate that children with peanut allergy have elevated sIgE to bystander foods that they are eating, suggesting that the mechanisms regulating production of IgE to foods is dysregulated in these children.