Correlation of IgE/IgG4 milk epitopes and affinity of milk-specific IgE antibodies with different phenotypes of clinical milk allergy(1)
Cow’s milk hypersensitivity is a common disease affecting 2.5% of infants in the first year of life, with approximately 60% of these milk disorders caused by IgE-mediated mechanisms. Although tolerance develops in the majority of children with IgE-mediated milk allergy by their teenage years, 15% to 20% have lifelong allergy. The peptide microarray immunoassay was used for examining serum samples from patients with peanut allergy and confirmed that antigenic areas identified by using this method correlated with areas defined by means of SPOTS membrane mapping. Patients with milk allergy and milk-tolerant patients demonstrated different epitope recognition patterns, with allergic patients having higher ratios of IgE to IgG4 binding than those tolerant to milk.
IgE and IgG4 binding frequencies to each peptide by group are shown. Subjects who were heated milk (HM) tolerant had IgE-binding patterns similar to those of subjects who had outgrown their milk allergy but IgG4-binding patterns that were more similar to those of the allergic group. IgE binding frequency was correlated with severity of symptoms during oral food challenge. There was no correlation between the number of IgG4 peptides and the severity of allergic reactions during challenge or between the number of IgE or IgG4 peptides bound and the eliciting dose during challenge.
Eight areas were identified as informative epitopes for IgE. The majority were located in αs1-casein, correlating with SPOTS-identified epitopes.
The corresponding IgE epitopes were identified on the protein sequence. There were no areas with a greater than 30% difference between groups for IgG4.
The competition assay using the caseins and β-lactoglobulin virtually eliminated all IgE binding from the HM-tolerant/outgrown group.
All allergic patients had a mixture of high- and low-affinity antibodies to different epitopes. There were 3 epitopes recognized by more than 50% of the allergic patients whose specific IgE antibodies to these epitopes were of relatively high affinity.
Patients with milk “allergy” have IgE antibodies that bind to certain peptide segments of milk proteins with high affinity and that are not competed away by native milk protein. In contrast, those who have transient allergy (outgrown) or are HM tolerant have low-affinity binding that is completely competed away by native milk protein. These results suggest that IgE affinity might play a role in the development of tolerance as well.The effect of IgE antibody affinity to Der p 2 on Der p 2–induced histamine release from human basophils and found that the sensitivity of histamine release was closely related to the affinity. Higher-affinity IgE binding to Der p 2 was associated with higher levels of basophil activation.