SPECIFICITY OF ELISA FOR IGG SUBCLASS ANTIBODIES AGAINST INHALANT ANTIGENS IN EARLY-CHILDHOOD

ELISA is increasingly used to measure antibodies in new circumstances. Recently, it has been applied to the measurement of IgG subclass anti bodies against common antigens in early childhood. These studies have raised concerns about the specificity of some of these assays. This pa per details the results of experiments which have assessed the specifi city of IgG 1 binding to allergens of dust mite (Dermatophagoides pter onyssinus) and ryegrass (Lolium perenne) pollen by inhibition ELISA in the sera of 2-year-old children of atopic parents. Six sera which sho wed binding of IgG 1 to D. pteronyssinus and six to L. perenne were us ed. All had IgG1 antibody against ovalbumin. In the children's sera, b inding to D. pteronyssinus was substantially inhibited by preincubatio n with the homologous antigen, but not with ovalbumin, thereby confirm ing the specificity of the assay. However, suppression of IgG1 binding to L. perenne with the homologous antigen was comparatively small, an d ovalbumin could cause an equivalent inhibition, indicating poor spec ificity. Furthermore, the level of IgG1 binding to L. perenne was clos ely 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 bindin g to ovalbumin was specific. Thus, binding IgG 1 in both adult and chi ld sera to D. pteronyssinus appeared to be specific, while child, but not adult, IgG1 binding to L. perenne showed poor specificity. This di sparity I may be due to differences in the affinities of the respectiv e antibodies, and I it illustrates the importance of determining assay specificity when making I measurements in early childhood.