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

Abstract

ELISA is increasingly used to measure antibodies in new circumstances. Recently, it has been applied to the measurement of IgG subclass antibodies against common antigens in early childhood. These studies have raised concerns about the specificity of some of these assays. This paper details the results of experiments which have assessed the specificity of IgG1 binding to allergens of dust mite (Dermatophagoides pteronyssinus) and ryegrass (Lolium perenne) pollen by inhibition ELISA in the sera of 2-year-old children of atopic parents. Six sera which showed binding of IgG1 to D. pteronyssinus and six to L. perenne were used. All had IgG1 antibody against ovalbumin. In the children's sera, binding to D. pteronyssinus was substantially inhibited by preincubation with the homologous antigen, but not with ovalbumin, thereby confirming the specificity of the assay. However, suppression of IgG1 binding to L. perenne with the homologous antigen was comparatively small, and ovalbumin could cause an equivalent inhibition, indicating poor specificity. Furthermore, the level of IgG1 binding to L. perenne was closely correlated to the level of IgG1 binding to ovalbumin (r = 0.98; P < 0.001). When the assay was reversed, IgG1 binding to ovalbumin was only slightly inhibited by L. perenne, indicating that most antibody binding to ovalbumin was specific. Thus, binding IgG1 in both adult and child sera to D. pteronyssinus appeared to be specific, while child, but not adult, IgG1 binding to L. perenne showed poor specificity. This disparity may be due to differences in the affinities of the respective antibodies, and it illustrates the importance of determining assay specificity when making measurements in early childhood.

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

“…As to the humoral response, several early studies clearly show that the IgG response is elevated in atopics (9)(10)(11)(12)(13). However, some authors claim that specific IgG antibodies against mites early in life occurs regardless of atopic status (8). The basis for this discrepancy (presence of IgG antibodies in both atopics and non-atopics) is unknown.…”

“…In non-atopic subjects, the involvement of the specific immune response to inhalant allergens is less clear. Some studies have found specific allergen antibodies (8) while other have failed to do so or found much lower 208 amounts (9)(10)(11)(12)(13). Here we scrutinised the antibody specific IgG responses to birch pollen, a widely spread and important inhalant allergen in Sweden, in sibling pairs discordant for atopy.…”