Significance of ovomucoid- and ovalbumin-specific IgE/IgG ₄ ratios in egg allergy

Background: The role of specific IgG ₄ antibodies in natural tolerance acquisition remains a matter of debate; the specific IgE/IgG ₄ ratio might add value to the measurement of absolute amounts of IgE for assessing the ongoing status of egg reactivity. Objective: We sought to determine the significance of IgG ₄ antibodies to ovalbumin (OVA) and ovomucoid (OVM) in egg-allergic children. Methods: One hundred seven egg-allergic children (mean age 6.9 years; range 1.6-18.6 years) were challenged to baked egg. The outcomes of the challenges were related to the level of specific IgE and IgG ₄ to OVM and OVA, component IgE/IgG ₄ ratios, and mediator release in a functional assay based on the rat basophil leukemia cell line. Results: Baked egg-reactive children had significantly higher OVA and OVM ratios of IgE/IgG ₄ and mediator release in the rat basophil leukemia-based assay than did tolerant children (P <.05 for both). The OVA- and OVM-specific IgE/IgG ₄ ratios and mediator release were correlated. In the receiver operating characteristic analysis, the areas under the curve for a logistic regression model including specific IgE and IgG ₄ to OVA and OVM were significantly greater compared with the areas under the curve for egg white-specific IgE and OVM-specific IgE. Conclusions: The balance between IgE and IgG ₄ to OVA and OVM has functional consequences. A model that includes the interactions between IgE and IgG ₄ to OVA and OVM accurately predicts reactivity to baked egg and warrants further investigation.