QUANTITATION OF ANTI-A AND ANTI-B IGG ANTIBODIES IN THERAPEUTIC IV IMMUNOGLOBULIN BY INDIRECT ELISA

An indirect ABO-ELISA was applied to quantitate anti-blood group A and B IgG antibodies present in 7 commercial intravenous immunoglobulin G (IVIg) preparations. The capturing antigen was substance A or B fixed to polystyrene microtiter plates. Bound anti-A and anti-B were revealed with mouse monoclonal anti-human isotype-specific antibodies detected in turn by goat anti-mouse alkaline phosphatase-conjugate. The data obtained with the IVIg preparations were compared to the data obtained with anti-A and anti-B IgG affinity purified on Biosynsorb® and results were expressed as μg specific anti-A/anti-B per g total IgG present in the respective IVIg. In 6 preparations in which anti-A was detectable, the lowest/highest concentrations of specific anti-A IgG found were 0.32 2.4 μg per g total IgG; thus one molecule specific anti-A IgG was found per 4.1-31 × 105 total IgG molecules. In the 7 preparations the anti-B IgG levels varied from 0.44 to 13.37 μg/g total IgG. The titer strength achieved by the same preparations in a hemagglutination test (HAT) varied 8-fold and regression analysis between ELISA and HAT results was significant (P < 0.05) for anti-A. It is likely that the higher sensitivity of ELISA and its direct measurement of antibody binding to antigen account for the wider scatter of ELISA results which makes this test suitable to quality contol of IVIg. © 1990.