A QUANTITATIVE ASSAY FOR SUBCLASSING IGG ALLOANTIBODIES IMPLICATED INHEMOLYTIC-DISEASE OF THE NEWBORN

Traditionally, Ige subclassing has been performed using qualitative as says. Quantitation of IgG subclasses may have prognostic value in eval uating alloimmunized pregnancies. A quantitative enzyme-linked immunos orbent assay (ELISA) was implemented for measuring IgG subclasses of r ed blood cell (RBC) antibodies (AB) isolated by adsorption/elution fro m the sera of alloimmunized pregnant women. The assay is a sandwich en zyme immunoassay using monoclonal antibodies specific for the relevant Ige subclasses and anti-human IgG peroxidase conjugate to quantitate the amount of bound IgG. The sensitivities of the assay for IgGI, 2, 3 , and 4, respectively, were 4, 23, 4 and 2 mu g/l. The results for eac h subclass for a given AB were expressed as a percentage of the total. In a series of pregnant mothers with ABs: E (4), Fy(a) (2), Jk(a) (1) and S (1), the mean percentage +/- ISD of each subclass was: IgG1 61 +/- 34; IgG2 14 +/- 22; IgG3 18 +/- 28 and IgG4 4 +/- 17. IgG1 or IgG3 accounted for greater than 50% of the AB subclass distribution in 5 c ases that resulted in hemolytic disease of the newborn (HDN). Although only a small number of samples was studied, changes in the concentrat ions of IgC1 or IgG3 during gestation suggest a correlation with the p resence or absence of HDN. The ELISA may be used to quantitate the IgG subclasses of RBC ABs and may be valuable in predicting the severity of HDN in alloimmunized pregnancies.