IMMUNOGLOBULINS IN THE AMNIOTIC FLUID AND FETUS

Abstract

Interest in the prenatal diagnosis of hypersensitivity disorders, immunodeficiency and intrauterine infections prompted this study of relationships between immunoglobulins (Ig) in amniotic fluids (AF) and corresponding maternal and cord sera. We collected aliquots of 134 AF obtained from amniocenteses and abortions performed for other medical reasons.The level of IgG in AF was lower than in paired cord serum even when corrected for total protein content. IgG antibodies to diphtheria toxin were detected in AF as early as 13 weeks gestation, and antibody per mg/IgG was generally similar in cord, maternal serum and AF. IgM was undetectable in all AF's even those concentrated 25x. IgD was detectable in a concentrated AF at 21 weeks of age, in which IgM and IgA were < 2 mg% indicated a lack of maternal blood contamination.In contrast to IgG, IgA in AF exceeded the corresponding cord level. AF IgA increased throughout gestation, while cord IgA remained low. Secretory component was detected in AF as early as 11 weeks. IgE constitutes a higher proportion of AF protein, than of maternal or cord serum. Both AF and cord IgE increased with gestational age. The IgE levels in paired cord and maternal sera were not correlated (correlation coefficient=.176). There was better correlation between AF and maternal IgE but best between AF and cord IgE, (correlation coefficient=.522 and p <.01). Secretion and active transfer appear to be important determinants of AF Ig levels.