Trajectories of class–switching‐related egg and cow's milk allergen‐specific immunoglobulin isotype formation and its modification by eczema with low‐ and high‐affinity immunoglobulin E during early infancy

INTRODUCTION: Allergen‐specific immunoglobulin isotype formation associated with immunoglobulin class‐switching during the lactation period is the immunological background for food allergy in infants. We analyzed the serial changes in the production of feeding type‐related egg‐ and milk‐specific immunoglobulin isotypes from birth to 6 months of age with or without eczema in 84 infants. METHODS: Allergen‐specific immunoglobulin G1 (IgG1), IgG2, IgG3, IgG4, IgA, and IgE levels of hen's egg and bovine milk were measured in cord blood and blood samples from infants at 2, 4, and 6 months of age by the densely carboxylated protein microarray. RESULTS: Formula and mixed feeding were associated with a rapid increase in cow's milk allergen‐specific immunoglobulins and feeding type‐related significant differences in casein‐specific immunoglobulin levels were detected. Breast and mixed feeding were associated with slow but significant increase in ovalbumin‐specific IgG1 and IgE levels, but not other immunoglobulins. We found two different immunoglobulin isotype formation at 6 months of age with low‐ or high‐affinity IgE against ovalbumin. One isotype formation pattern had relatively high ovalbumin‐specific IgG1 levels, detectable IgG2, and low‐affinity IgE, while the other had low ovalbumin‐specific IgG1 levels, undetectable IgG2, and high levels of high‐affinity IgE. The incidence of eczema was significantly higher in the latter pattern (84.6%), compared with the remaining infants (42.2%). CONCLUSIONS: Feeding practice‐related allergen sensitization and immunoglobulin isotype formation were identified during the lactation period. The development of eczema during the lactation period could potentially modify the immunoglobulin isotype formation with high levels of high‐affinity IgE.