Analysis of allergen-specific T cell and IgE reactivity in milk and egg allergic children in response to progressive forms of baked milk and egg food extracts

Abstract

Abstract Egg and milk allergy are among the most common food allergies in young children and are commonly outgrown. Developing tolerance is often clinically monitored by food challenge with cooked forms of egg and milk. This study characterizes IgE and T cell reactivity to four progressively cooked food extracts from egg and milk. Egg and milk-containing food extracts were prepared from most to least cooked foods: egg muffin, meat balls frittata and raw egg; milk muffin, pizza cheese, custard and raw milk. IgE reactivity against extracts was determined by western blot and protein-specific IgE reactivity was quantified. T cell reactivity against the extracts was determined by FluoroSpot (IL-5, IFNγ and IL-10) after 24h restimulation following a two week in vitro expansion culture. IgE reactivity varied between extracts, in a protein-specific manner. For milk, a protein band at 14 kDa corresponding in size to Bos d 4 is observed most strongly in raw milk and cheese extract, while being less reactive in custard and milk muffin. In contrast, a band at 67 kDa, corresponding to Bos d 6 in size, is most intense in milk muffin compared to raw milk, cheese and custard. For egg, trends are more consistent across the different proteins, with egg muffin showing most IgE reactivity throughout. Analysis of T cell responses showed highest IL-5 production for raw milk extract compared to custard (p=0.058), cheese (p=0.039) and muffin (p=0.097). No differences were observed for IFNγ and IL-10. For egg, no differences between extract-induced T cell reactivity was observed. Both IgE and T cell reactivity is readily detectable against food extracts from baked forms of egg and milk. Immunological reactivity is not necessarily associated with the degree of cooking.