Terasaki-ELISA for murine IgE antibodies. II. Quantitation of absolute concentration of antigen-specific and total IgE.

A Terasaki tray-based ELISA system was developed for the quantitative measurement of antigen-specific and total IgE antibodies in 5 microliter samples of mouse serum dilutions. The assay was based upon non-competitive binding of mouse IgE antibodies between the immobilized appropriate antigen or capture antibodies and the detecting rabbit antibodies. A conjugate of protein A-labelled beta-galactosidase and the fluorigenic substrate methylumbelliferyl-beta-D-galactoside were used as a detecting system. The resulted fluorescence could be measured rapidly and automatically using an inverted micro-fluorimeter. These measurements were automatically transformed into absolute concentrations by a microprocessor-based program using a four-parameter logistic function and an absolute IgE standard. The assay was shown to have a detection limit of 0.04 ng/ml and a range of linearity of 0.04-20 ng/ml, which is sufficient to measure IgE concentrations in mouse serum.