Placental transport of maternal immunoglobulin G in pregnancies at risk of Rh (D) hemolytic disease of the newborn.

PROBLEM: The following questions were addressed: Is the placental transport of immunoglobulin (Ig)G, IgG1, and IgG3 diminished in pregnancies at risk of hemolytic disease of the newborn? Is the placental transport of IgG, IgG1, and IgG3 correlated with the hemoglobin concentration in the fetus and AutoAnalyzer (AA) quantitations of maternal anti-D? METHOD OF STUDY: IgG concentrations were determined retrospectively in 41 paired fetal/maternal (f/m) samples in 31 Rh (D) alloimmunized pregnancies. IgG1 and IgG3 concentrations were determined in those 23 cases in which the results of fetal hemoglobin concentration and quantitations of maternal anti-D were available. The results were compared with values found in normal pregnancy and correlated with maternal anti-D AA quantitations and fetal hemoglobin concentrations. RESULTS: Fetal IgG, IgG1, and IgG3 concentrations, and the corresponding fetomaternal ratios in Rh (D) alloimmunized pregnancies, increased with gestational age according to the following formulas (obtained by simple regression): Fetal IgG = -8.846 + 0.491.gestational age (GA), (R2 = 0.544); fetal IgG = 10.021 + 0.46.GA (R2 = 0.463); fetal IgG3 = -0.865 + 0.039.GA, (R2 = 0.327); f/m IgG = -1.006 + 0.054.GA, (R2 = 0.557); f/m IgG1 = -1.876 + 0.085.GA, (R2 = 0.654); f/m IgG3 = -0.199 + 0.026.GA, (R2 = 0.146). CONCLUSIONS: The placental transport of IgG, IgG1, and IgG3 in women with Rh (D) immunizations is not diminished compared with normal pregnancy. However, AA quantitations of anti-D are inversely correlated with f/m IgG ratio, f/m IgG1 ratio, and fetal IgG and IgG1 concentrations (P = 0.002, P = 0.004, P = 0.02, and P = 0.02 respectively). The placental transport of IgG3 is significantly higher in pregnancies at risk of hemolytic disease of the newborn compared with IgG3 concentrations in normal pregnancy.

Concentration of anti-D antibodies in Rh(D) alloimmunized pregnant women, as a predictor of anemia and/or hyperbilirubinemia in their newborn infants.

OBJECTIVES: To define a simple, safe and reliable program for the monitoring of anti-D alloimmunized pregnancies by analysis of the covariation between antenatal values of the titer and the concentration of anti-D antibodies in maternal serum, the deltaOD(450 nm) in amniotic fluid samples, and the levels of B-hemoglobin and S-bilirubin in the newborns at birth. SUBJECTS: Ninety-three Rh(D) negative women with anti-D antibody titers > or = 16 who, after the completed 34th gestational week, gave birth to Rh(D) positive babies with a positive direct antiglobulin test. METHODS: The titers and the concentrations of anti-D antibodies in maternal serum were determined by standard procedures every second week from the 25th week of gestation. In 47 of the 93 women, deltaOD(450 nm) in amniotic fluid was determined at least once. All antenatal values used in the study were determined within 14 days before delivery. RESULTS AND CONCLUSION: Maternal serum antibody titers < or = 32 or > or = 1000 could in themselves well predict unaffected and affected newborns. Antibody titers between 64 and 512 could not accurately predict newborns with or without hemolytic disease. As a complementary monitoring test, determination of the deltaOD(450 nm) was found to be less accurate when compared to determination of the concentration of anti-D antibodies. In order to monitor Rh(D) alloimmunized pregnancies, determination of the concentration of anti-D antibodies may possibly replace determination of deltaOD(450 nm).

Application of the gel test in IgG subclassing--a comparison of two agglutination assays.

BACKGROUND AND OBJECTIVES: IgG subclasses of anti-D seem to play some role in hemolytic disease of the newborn, but there has been disagreement as to its exact nature. The aim of our study was to evaluate a new technique for IgG subclassing of anti-D and to compare it to an established test. MATERIALS AND METHODS: In 31 cases of RhD immunization, we have compared two simple agglutinating assays for subclassing anti-D: an established V-well microtiter tray assay and a new gel test assay. Polyclonal rabbit anti-IgG agglutinating antibodies were tested against sensitized D-positive red blood cells by both assays. RESULTS: The anti-D concentration in tested sera varied between 0.1 and 81 micrograms/ml (0.5-405 IU/ml). Both assays were simple to perform and the results correlated well. CONCLUSIONS: The gel test had two advantages: quick performance and easy interpretation.

Flow-cytometric quantitation of anti-D antibodies.

OBJECTIVES: Quantitation of Rh antibodies is important clinically in predicting the risk of hemolytic disease of the newborn. We describe a flow cytometry method for the quantitation of anti-D antibodies that we developed in parallel to a recently described method. METHODS: As a secondary antibody we used whole IgG instead of Fab molecules. The advantages, besides lower cost, include a strong fluorescence signal with no need for amplification, and the possibility of diluting samples to minimize the risk of agglutination by IgM antibodies. We did extensive studies on reproducibility. RESULTS: Reproducibility was superior to the autoanalyzer method. The two methods were roughly in agreement in estimating low, medium, or high levels of anti-D with a correlation coefficient of 0.89. The autoanalyzer measures the in vitro agglutination of all anti-D antibodies whereas flow cytometry measures the amount of IgG anti-D bound to red cells, which is more like the in vivo situation. CONCLUSION: Further studies in a clinical setting will show whether flow-cytometric quantitation may improve the diagnostic value of anti-D concentration measurement.

Severe Rh(D) immunization: anti-D quantitation and treatment possibilities during pregnancy and after birth.

An extremely aggressive Rh(D), (C) and Kell alloimmunization during pregnancy is reported. Exceptionally high concentrations of anti-D were observed in the mother, in the fetus and in the amniotic fluid, indicating an active transport across the placenta and a passive excretion into the amniotic fluid. Treatment during pregnancy included maternal plasmapheresis and high-dose intravenous immunoglobulin. Intravascular transfusions were given to the fetus. Postpartum the newborn was given immunoglobulin, one exchange transfusion and four top-up transfusions. In the newborn the elimination rate of anti-D could be followed. Not until almost 4 months postpartum did the anti-D concentration drop below the level of detection. This coincided with an elevated reticulocyte production and appearance of the child's true blood group in parallel with ceasing need for blood transfusions. Elimination rate and absolute anti-D values can be used as a prognostic tool to predict the need of blood transfusions. Immunoglobulin treatment can also be considered as an optional form of treatment in newborns affected by alloimmunization.

HLA phenotypes and severe Rh(D) immunization.

Blood samples from 24 Rh(D) immunized women were analyzed for antibody titers and quantification of anti-D. The HLA-DR and -DQ polymorphisms were identified as RFLP. In 11 women with titers 16-256 the HLA-DQB1 allele *0201 was found in 18%, i e as in a reference population. In 13 women with titers > or = 512 the HLA-DQB1 allele *0201 was found in 85% indicating a correlation between severe Rh(D) immunization with high titers/quantification values and the DQB1 allele *0201. In this group the fetus was severely affected by the immunization and treatment during pregnancy was frequently needed. HLA phenotyping of women known to have anti-D antibodies early in pregnancy seems to be an effective way to assess the probability of severe hemolytic disease of the newborn.

Evaluation of standard parameters to predict exchange transfusions in the erythroblastotic newborn.

During the time period 1983-90, 91,300 consecutive pregnancies were monitored for red cell alloimmunization. Once revealed, the immunizations were followed by means of repeated maternal antibody titers, maternal anti-D quantitation in D-immunized women, amniotic fluid bilirubin levels and fetal hemoglobin concentrations. High dose intravenous immunoglobulin and/or intrauterine intravascular transfusion was given to prevent or treat fetal anemia. Delivery was induced for all before term when antibody titers were > or = 16. Nevertheless, exchange transfusions were performed in 41 newborns with mothers alloimmunized to Rh(D), Rh(c), Rh(E) and Kell antigens. Eight of the mothers were Rh(D) positive. Phototherapy alone was given to 35 newborns. Both maternal antibody titers and amniotic fluid bilirubin levels were found to be unreliable to predict the need of exchange transfusions in the newborns. Quantitation of maternal anti-D concentration was found to be significantly better predicting 62% at a cut-off level of 0.7 microgram/mL. Analysis of fetal hemoglobin concentration by cordocentesis is the only direct method to evaluate the degree of fetal affection, and should probably be performed when maternal antibody titers are > or = 64, anti-D concentration is > or = 0.7 microgram/mL and data indicate an aggravation of the immunization.

Evaluation of a new Swedish protocol for alloimmunization screening during pregnancy.

Screening protocols for alloimmunization during pregnancy usually make a difference between primi- and multigravidae as well as between Rh(D) negative and Rh(D) positive pregnant women. We have evaluated a new screening program including antibody tests at 25 and 35 gestational weeks only, for all, and regardless of Rh(D) group. During the time period 1983-89, 78,300 consecutive pregnancies were tested. Red cell antibody immunizations were detected in 287 (0.37%) pregnancies subdivided into fourteen different red cell IgG antibody specificities. Significant antibody titers (defined as IAT or enzyme titers > or = 8) were observed in 225 pregnancies, where 127 (56%) were previously unknown. A majority (63%) of the new immunizations occurred among the Rh(D) positive pregnant women. All newborns that needed phototherapy or exchange transfusion due to alloimmunization were recognized at the time of delivery. We conclude that antibody screening tests at 25 and 35 gestational weeks for both Rh(D) negative and positive pregnant women is sufficient, effective and a safe procedure for the fetus as well as for the mother.

Acute dapsone intoxication: a case treated with continuous infusion of methylene blue, forced diuresis and plasma exchange.

A case of massive dapsone poisoning (15 g) in a 26 year old man is reported. The patient exhibited high plasma dapsone concentration, marked methemoglobinemia, and signs of hemolysis. He recovered completely after intensive treatment with methylene blue, activated charcoal, forced diuresis, and plasma exchange. In order to avoid overdosage of methylene blue it is concluded that this substance should be given by continuous intravenous infusion in cases with severe methemoglobinemia. This way of administration caused a steady decrease in the methemoglobin concentration compared to intermittent administration. Plasma exchange was of minor benefit, probably due to the large distribution volume of dapsone.