IgG subclasses and Gm allotypes of anti-D antibodies during pregnancy: correlation with the gravity of the fetal disease.

The IgG subclasses and the Gm allotypes of anti-D antibodies were studied in 103 isoimmunized pregnancies with Rh-positive infants. No allelic exclusion phenomena were observed in patients heterozygous for the studied genes. An analysis of the correlation between the severity of fetal disease and the type of anti-D antibodies shows a greater hemolytic action of the IgG1 subclass and, within this group, those marked by the Gm(4) allotype. These results suggest that the prognostic value of anti-D antibody titers during pregnancy could be modulated by a study of the IgG subclasses and their allotypes.