Specificity of ELISA for IgG subclass antibodies against inhalant antigens in early childhood

IgG subclass antibody responses to birch pollen in sibling pairs discordant for atopy

Birch pollen allergen specific IgG and IgE antibodies were analysed in the sera of fourteen sibling pairs discordant for atopy. In addition, eight unrelated children free of atopic disease were included in the study. The presence of Bet v 1 specific antibodies in the sera were analysed by an immunoblotting assay. All but one (13/14) of the atopic children had detectable anti-Bet v 1 antibodies of the IgG1 and IgG4 subclasses. The child lacking IgG1 and IgG4 antibodies to Bet v 1 was the only allergic child lacking IgE to Bet v 1. In contrast, only one of the non-atopic siblings (1/14) displayed detectable IgG1 antibodies to Bet v 1. Furthermore, among the non-atopic siblings none (0/14), had detectable IgG4 antibodies to Bet v 1. In the unrelated control group no detectable IgG1 or IgG4 anti-Bet v 1 were detected (0/8). Thus of the non-atopic children only one out of 22 children displayed IgG1 anti-Bet v 1 antibodies. Taken together, it appears that the non-atopic children in general have no/low allergen specific IgG to birch pollen.

Binding affinities of allergens from pollen, mites, and house dust for specific IgG subclass antibodies

The distribution and affinity of IgG subclasses against various aeroallergens were assessed by inhibition of specific antibody binding. Two parameters from the dose-response curves were taken as indicative of antibody affinity: the point of 50% inhibition and the value of the slopes on double-log plots. It was found that IgG4 antibody specific for aeroallergens (i.e., from pollens of several species of Gramineae, Olea europaea, and Parietaria judaica and from house dust) usually exhibits high affinity, except for Dermatophagoides pteronyssinus. High binding affinity was also displayed by IgG1 subclass antibodies against the allergens of O. europaea and P. judaica. Distinct IgG subclass affinity profiles were observed for the allergens of grass pollen (i.e., Holcus lanatus) and dust mites (i.e., D. pteronyssinus). These results demonstrate that IgG subclass distribution, as well as antibody affinity, depends on the nature of the sensitizing allergen.