Quantitative measurement of serum allergen-specific IgE on protein chip

Type I allergy is an immunoglobulin E (IgE)-mediated hypersensitivity disease inflicting more than quarter of the world population. In order to identify allergen sources, skin provocation test and IgE serology was performed using allergen extracts. Such process identifies allergen-containing sources but cannot identify the disease-eliciting allergenic molecules. Recently, microarray technology has been developed for allergen-specific IgE detection using rolling circle amplification. This study was carried out to evaluate protein chip technology for the quantitative measurement and limits of sensitivity of multiple allergen-specific IgE by an immunofluorescence assay. Significance of positive calibrators was tested using purified human IgE. Dermatophagoides pteronyssinus (Dp), egg white, milk, soybean, and wheat were used as allergens and human serum albumin as negative control. Sensitivity and clinical efficacy of protein chip were evaluated using allergy immune serum for Dp. The fluorescent intensities for purified human IgE as calibrator were well correlated with the concentrations of human IgE. Two-fold dilution of serum allowed an optimal reaction with Dp (1 mg/ml) at which serum Dp-specific IgE levels by protein chip were compatible with those by UniCap(R). The sensitivity of protein chip in this study was found at level of 1 IU/ml of IgE. Dp-specific IgE levels by protein chip correlated well with those of UniCap(R) by comparing 10 atopic dermatitis. Additional 18 sera were tested for above multiple antigens other than Dp and significant results were obtained for many antigens as well as Dp. These results indicated that spotting of heterogeneous protein mixture on protein chip and the quantitative measurement of serum allergen-specific IgE levels using immunofluorescence assay can be successfully applied in the clinical laboratory for the diagnosis of allergy and could be applied to diagnosis of autoimmune and infectious diseases.