Relationship between allergic status and specificity of IgG antibody to inhaled allergens: the grass pollen model

We have previously reported that IgG antibodies from healthy individuals and patients suffering from non-seasonal mite allergy bind to different sets of epitopes on Der p 1, allowing almost complete discrimination of the populations.

To confirm this observation in a seasonal allergy model where a clear relationship between allergic symptoms and exposure to the offending agent is established. To investigate whether the pattern of modified specificity is related to the differences in IgG subclass hierarchy usually exhibited by nonallergic and allergic populations.

The capacity of individual sera from patients allergic to grass pollen and healthy individuals, including grass pollen-sensitized subjects, to prevent the binding of pooled IgG, IgG1, and IgG4 fractions from grass pollen-allergic patients and healthy individuals to solid-phase bound grass pollen antigen was evaluated in enzyme-linked immunosorbent assay (ELISA) using streptavidin-biotin technology. Specificity controls were performed using sera from patients allergic to cat dander and house dust mite.

The capacity of sera to prevent the antigen binding of allergic IgG averaged 84 +/- 5% for allergic sera and 53 +/- 6% for healthy sera (P < 0.001 by one-way anova). Conversely, using the antigen-binding capacity of healthy control IgG as reference, percentage inhibitions averaged 46 +/- 9% in grass pollen-allergic subjects compared with 80 +/- 4%, 82 +/- 2% in healthy individuals, and mite- and cat-allergic patients, respectively, resulting in two well-separated populations (P < 0.0001 by one-way anova). Similar results were found regardless of whether pooled IgG1 or IgG4 were used.

Together with previous data, our results define a new type of humoral signature in the immune response to inhaled allergens. Allergic and healthy status differ not only in the presence or absence of specific IgE antibody but also in the preferential expression of distinct IgG specificities that are better correlated with clinical manifestations and are unrelated to subclass distribution.