Erythrocytes In Maternal Blood Research Articles

Correlation of lipid peroxidation and ATP enzyme on erythrocyte membrane with fetal distress in the uterus in patients with intrahepatic cholestasis of pregnancy.

This paper aims to investigate the correlation of lipid peroxide in erythrocytes and ATP (Adenosine Triphosphate) enzyme activity of erythrocyte membrane with fetal distress in patients with intrahepatic cholestasis of pregnancy (ICP). Forty-three patients with ICP treated at Jining No. 1 People's Hospital were enrolled as a study group, and another forty healthy parturient women in the same period were enrolled as a control group, to extract their elbow venous blood and fetal umbilical cord blood. Thiobarbituric acid (TBA) was used to detect superoxide dismutase (SOD) activity of erythrocytes, malondialdehyde (MDA) activity in plasma, Na+-K+-ATP enzyme activity and Ca2+-Mg2+-ATP enzyme activity of erythrocytes, which were compared between the study and control groups. The correlation of MDA, Na+-K+-ATP enzyme and Ca2+-Mg2+-ATP enzyme activities with fetal distress in the study group was analyzed, and the correlation of MDA with Na+-K+-ATP enzyme activity was investigated. SOD and MDA activities of erythrocytes in maternal blood of the study group were significantly higher than those in the control group (p<0.05, p<0.001, respectively), but MDA activity in umbilical cord blood of the study group was markedly higher than that in the control group (p<0.001). Na+-K+-ATP enzyme and Ca2+-Mg2+-ATP enzyme activities of maternal and fetal erythrocytes of the study group were remarkably lower than those of the control group (p<0.001). MDA in the fetal distress group was significantly higher than that in the no fetal distress group in the study group (p<0.001). Na+-K+-ATP enzyme activity was negatively correlated with MDA concentration in maternal and fetal erythrocytes of patients with ICP (both p<0.001). Lipid peroxidation in patients with ICP will affect ATP enzyme activity of erythrocyte membrane, and the down-regulation of ATP enzyme activity in umbilical cord blood of patients with ICP may cause fetal distress in the uterus.

Polyunsaturated Fatty Acid Levels in Maternal Erythrocytes of Japanese Women during Pregnancy and after Childbirth

Background: The transport of polyunsaturated fatty acids (PUFAs), such as arachidonic acid (ARA, 20:4n-6) and docosahexaenoic acid (DHA, 22:6n-3), to the fetus from maternal stores increases depending on the fetal requirements for PUFA during the last trimester of pregnancy. Therefore, maternal blood PUFA changes physiologically with gestational age. However, the changes in PUFA levels in maternal blood erythrocytes during pregnancy and after childbirth have not been fully investigated in a fish-eating population. Objective: To examine the changes of ARA and DHA levels in maternal erythrocytes with the progress of pregnancy and the relationship between maternal and umbilical cord erythrocyte PUFA levels in pregnant Japanese women who habitually eat fish and shellfish. Design: This study was performed as a part of the adjunct study of the Japan Environment and Children’s Study (JECS). The participants were 74 pregnant women. The maternal blood samples were collected at 27, 30, and 36 weeks of pregnancy, and 2 days and 1 month after delivery, and umbilical cord blood was collected at delivery. The fatty acid levels of erythrocytes in these blood samples were determined. Results: ARA and DHA levels in maternal erythrocytes tended to decrease with the progress of pregnancy. While the DHA level decreased further after delivery, the ARA level returned to the value at 27 weeks of pregnancy within 1 month after delivery. The n-3 and n-6 PUFA levels in maternal erythrocytes at 27, 30, and 36 weeks of pregnancy were significantly positively correlated with the corresponding fatty acid levels in umbilical cord erythrocytes. Conclusion: The present findings showed a significant change in erythrocyte PUFA levels during pregnancy and after childbirth in a fish-eating population. The PUFA levels of maternal blood after the second trimester may be a reliable marker for predicting PUFA levels in infants’ circulating blood.

Reference Values of Fetal Erythrocytes in Maternal Blood During Pregnancy Established Using Flow Cytometry

The aim of our study was to assess the fetal RBC count in maternal blood during uncomplicated pregnancies from 26 weeks onward. We used a flow cytometric method specifically designed for use in a routine hematology analyzer. Pregnant women were recruited through midwives. The participating laboratories used the FMH QuikQuant method (Trillium Diagnostics, Brewer, ME) in a CELL-DYN Sapphire hematology analyzer (Abbott Diagnostics, Santa Clara, CA). The method is based on a monoclonal antibody to hemoglobin F. Flow cytometric data were analyzed by 2 independent observers. The 95th percentile reference range was estimated according to Clinical and Laboratory Standards Institute guidelines. A total of 236 samples were statistically analyzed. Gestational ages ranged from 21.6 to 41 weeks (mean, 32.0 weeks), and the fetal RBC count in maternal blood ranged from 0.00% to 0.50% (median, 0.025%). The fetal RBC count in maternal blood shows no correlation with gestational age. The established reference range during normal pregnancy is less than 0.125%.

Cytometry and Rhesus: not only for haemolytic disease of the newborn.

Since the 1960s, when passive immunoprophylaxis with intramuscular administration of adequate doses of anti-D immunoglobulin was introduced to prevent maternal-foetal Rhesus (Rh) immunisation, the number of cases of haemolytic disease of the newborn (HDN) has decreased dramatically1–2. The most widely used test to detect the presence of foetal erythrocytes in maternal blood is the acid elution method described by Kleihauer-Braun-Betke3. Since the 1990s, other methods have been adopted for routine laboratory assessment of the degree of foetal-maternal haemorrhage (FMH), such as flow cytometric search for Rh-positive erythrocytes with monoclonal antibodies4 and the agglutination test on a card (gel agglutination technique, GAT). In our laboratory, we use the flow cytometric method, which selectively quantifies the circulating Rh-positive erythrocytes, by using a monoclonal antibody directed to the erythrocyte D antigens (Quanti-D Pe, Millipore). This method has the obvious advantages of sensitivity, specificity, objectivity and is faster than the traditional one5–6. The extreme specificity of the test has led us to adopt it not only to quantify the extent of FMH in order to prevent HDN, but also for other purpose. Here we illustrate two cases in which the use of flow cytometry helped us to explain clinical problems and to detect transfusion errors.

Identification of feto-maternal haemorrhage around labour using flow cytometry immunophenotyping

Objective To determine the normal range of feto-maternal haemorrhage (FMH) due to labour, and to investigate if the type of delivery might influence the volume of FMH. Study design In a prospective cohort trial setting we studied 346 women in their 3rd trimester of gestation. Women were classified according to the type of delivery: vaginal, instrumental and caesarean section. Fetal erythrocytes in maternal blood were measured by flow cytometry immunophenotyping using a fluorochrome-conjugated monoclonal antibody against fetal haemoglobin. For each woman, two blood samples were studied; one pre-labour and one post-labour. The difference between FMH values obtained post- and pre-delivery was established as FMH due to delivery. Results FMH due to labour ranged between <0.01 and 25.19 ml, being <1.15 ml in 96.13% of cases. This value was established as the upper limit of normal FMH due to delivery. No statistical significance was found between the volume of FMH and type of delivery. Analyzing distributions of groups, most data followed a normal distribution, apart from some patients who had higher volume of FMH. Among these patients caesarean sections showed a higher FMH volume, with statistically significant differences between vaginal deliveries and caesarean sections ( p = 0.001), and between instrumental deliveries and caesarean sections ( p = 0.008). Conclusions FMH due to labour is small. The route of delivery could not be established as a risk factor for FMH but caesarean section increases the risk of suffering a higher amount of transplacental bleeding.

Fetal Gender Determination and BclI Polymorphism Using Nucleated Erythrocytes in Maternal Blood

This study demonstrated determination of fetal gender from nucleated red blood cells (NRBCs) in maternal blood and attempted to apply prenatal diagnosis of hemophilia A using BclI DNA polymorphism. Venous blood was drawn from 20 pregnant women, and NRBCs were recovered by magnetic activated cell sorting and anti-GPA (glycophorin A) immunostaining. After microdissector isolation of the NRBCs, primer extension preamplification (PEP) and nested PCR of the amelogenin gene were performed to determine fetal gender. We also performed PEP and nested PCR of BclI polymorphism to verify the validity of prenatal diagnosis of hemophilia A. DNA amplification was achieved in 107 cells (51.9%) and fetal gender determined with 65.0% accuracy. Unfortunately, we could not verify the validity within the scope of this study. However, in a larger number of cases that are informative in BclI polymorphism, we will be able to identify patients affected by hemophilia A using fetal NRBCs in maternal blood.

Simple non-invasive prenatal detection of Hb Bart's disease by analysis of fetal erythrocytes in maternal blood

To investigate a simple non-invasive technique for early detection of Hemoglobin (Hb) Bart's disease. Maternal blood smears from 8 known Hb Bart's pregnancies and 40 at-risk pregnancies were investigated. Maternal peripheral blood smears were stained with fluorescence-labeled monoclonal antibodies against alpha- and embryonic zeta-globin chains. Fetal nonnucleated red blood cells, stained with anti-zeta but not with anti-alpha globin antibodies were found in 15 out of 16 affected pregnancies but were not detected in 23 out of 24 unaffected pregnancies. Results showed that non-invasive immunofluorescence staining of maternal blood is a feasible approach for screening Hb Bart's disease before ultrasound manifestation in affected pregnancies.

Chorionic villus sampling increases the alpha-fetoprotein level but not the number of fetal erythrocytes in maternal blood

NOT THE NUMBER OF FETAL ERYTHROCYTES IN MATERNAL BLOOD DENISE PELIKAN, SICCO SCHERJON, WILMA MESKER, GODELIEVE GROOT SWINGS, HANS TANKE, HUMPHREY KANHAI, Leiden University, Obstetrics, Leiden, Netherlands, Netherlands, Leiden University, Molecular Cell Biology, Leiden, Netherlands, Netherlands OBJECTIVE: To investigate the relation between alpha-fetoprotein (AFP) levels and the number of fetal erythrocytes in maternal blood before and after chorionic villus sampling (CVS). STUDY DESIGN: Blood samples of 53 women between 11 and 13 gestational weeks undergoing CVS, were collected 15 minutes before and after CVS. All pregnancies were cytogenetically normal. A biopsy forceps (n = 47) and a canula (n = 3) were used for transcervical CVS. An aspiration needle (n = 3) was used for transabdominal sampling. The AFP measurements were performed in a single run using the Chemiluminescent Microparticle Immunoassay. Supervised automated microscopy of Kleihauer-Betke stained slides was applied to quantify fetal erythrocytes. Per sample G 2.0x106 cells were evaluated. RESULTS: AFP measurements before and after CVS were obtained in 48 patients, whereas paired slides were complete in 50 patients. The mean AFP level before CVS was 13.9 mg/L (range 6.4-36.4, median 11.7, SD 7.3, SEM 1.1, 95% CI 11.8-16.0) and after CVS 37.2 mg/L (range 8.2-241.7, median 18.4, SD 46.4, SEM 6.7, 95% CI 23.7-50.7), indicating a significant increase of the AFP level in maternal plasma after CVS (Wilcoxon signed ranks test, P ! .0001). The mean number of fetal erythrocytes before CVS was 1.5 (range 0–24, median 0, SD 3.8, SEM 0.5, 95% CI 0.4–2.6) and after CVS 2.0 (range 0 – 23, median 1.0, SD 4.4, SEM 0.6, 95% CI 0.7–3.2). There was no significant increase in the fetal erythrocyte count before versus after CVS (Wilcoxon signed ranks test, P = .327). Consequently, the correlation between the fetal erythrocyte difference before and after CVS and the AFP level difference was not significant (r = 0.13, P = .39). CONCLUSION: Although an increase was found in AFP levels after CVS, no increase in fetal erythrocytes could be detected. This suggests that the CVS procedure results in a leakage of proteins due to placental tissue damage, rather than increased trafficking of fetal cells through the placental barrier. 229 RANDOMIZED COMPARISON OF SUBCUTANEOUS TISSUE REAPPROXIMATION ALONE AND IN COMBINATION WITH SUBCUTANEOUS DRAIN IN OBESE WOMEN UNDERGOING CESAREAN DELIVERY PATRICK RAMSEY, ANNA WHITE, DEBRA GUINN, GEORGE LU, LINDA FONSECA, ASHLEY CASE, DWIGHT ROUSE, University of Alabama at Birmingham, Obstetrics/Gynecology, Birmingham, Alabama, Northwest Perinatal Center and Women’s Healthcare Associates, Obstetrics/Gynecology, Portland, Oregon, Obstetrix Medical Group of Kansas & Missouri, Kansas City, Missouri, University of Texas Health Science Center at Houston, Obstetrics, Gynecology and Reproductive Sciences, Houston, Texas OBJECTIVE: To compare the efficacy of subcutaneous (SQ) suture reapproximation alone to suture plus SQ drain for the prevention of wound complications in obese women undergoing cesarean delivery. STUDY DESIGN: We conducted a prospective multicenter randomized trial of obese women undergoing cesarean delivery. Women preoperatively consented and only those with R4 cm of SQ thickness documented at fascial closure were randomized to either SQ suture closure alone (N = 148) or suture plus SQ drain (N = 132). Women receiving the drain had it placed to bulb suction and was removed at 72 hrs or earlier if output !30 mL/24 hour. The primary study outcome was a composite wound complication rate (defined by any of the following noted at the wound assessment: wound dehiscence, seroma, hematoma, or abscess). RESULTS: From 04/01-07/04 a total of 280 women were enrolled. Ninety-four percent of women (264/280) had a follow-up wound assessment. Both groups were similar with respect to age, parity, weight, cesarean indication, diabetes, steroid/antibiotic use, chorioamnionitis, and SQ thickness. The overall composite wound complication rate was 16.9% (24/142) in the suture group and 23.0% (28/122) in the suture + drain group (RR 1.4: 95% CI 0.8-2.2, P = .22). Individual wound complication rates are shown in the Table. CONCLUSION: The additional use of a SQ drain to a standard SQ suture reapproximation technique is not effective for the prevention of wound complications in obese women undergoing cesarean delivery.

Rh-prophylaxis in early abortion

Rh-prophylaxis in early abortion

Use of antibodies against the human antigen of erythroblasts for the detection of nucleated erythrocytes in the maternal circulation.

In the present study, we tried to detect nucleated erythrocytes in maternal blood by means of the HAE9 antibody that binds to the antigen of erythroblasts (Ag-Eb) on nucleated erythroid cells. Umbilical cord blood and placental cells, which are known to contain a high number of nucleated erythrocytes, indeed demonstrated a high percentage of Ag-Eb-positive cells. In comparison, HAE9 stained up to 4.5% of the peripheral blood cells collected from pregnant women, but not those of nonpregnant women or normal men. These results, demonstrating a simple and reliable method for the identification of nucleated erythrocytes in the maternal circulation using the anti-Ag-Eb antibody, might open new possibilities for the detection of nucleated erythrocytes in maternal blood.

Rare event selection of fetal nucleated erythrocytes in maternal blood by flow cytometry.

A noninvasive method of prenatal genetic diagnosis requires fetal cell selection from the maternal circulation that allows efficient recovery for analysis by fluorescence in situ hybridization (FISH). We have solved several problems that negatively affect the isolation and FISH analysis of fetal nucleated red blood cells (nRBCs) in the maternal circulation. The use of glycophorin A (Gly A) antibodies (Abs) for selection is problematic because all five monoclonal antibodies (mAbs) tested caused agglutination of non-nRBCs, thereby changing both light scatter and fluorescence properties of cells by flow cytometry. Because the number of non-nRBCs is variable after Ficoll separation, isolation of nRBCs could be compromised severely by agglutination of nucleated cells with nonnucleated cells, causing them to shift light scatter and fluorescence properties. Several methods for the removal of unwanted maternal white blood cells with CD45 mAbs were also evaluated. Magnetic bead depletion was found to interfere with FISH detection because of residual bead debris after sorting. By contrast, removal of CD45+ cells by a panning technique eliminated this problem. Positive selection methods based on CD71, CD45, and LDS-751 staining and detection of fetal cells by gamma globin expression were also analyzed. Fetal cells were detected by FISH in 11 of 19 (CD71 selection) and in 13 of 15 (gamma selection) random pregnancies. These data support the possibility of a noninvasive method for isolation and analysis of fetal cells for prenatal diagnosis.

Rare event selection of fetal nucleated erythrocytes in maternal blood by flow cytometry

Rare event selection of fetal nucleated erythrocytes in maternal blood by flow cytometry

Diagnosing and preventing inherited disease: Nucleated erythrocytes in maternal blood: quantity and quality of fetal cells in enriched populations

The discovery of nucleated erythrocytes in maternal circulation provides a potential source for non-invasive prenatal diagnosis. We have evaluated the use of a three-stage procedure to determine the number of cells that are of fetal rather than maternal origin. First, monoclonal antibodies specific for CD45 and CD14 were used in conjunction with a magnetic (MACS) column to deplete unwanted leukocytes from maternal blood. This was followed by a positive MACS enrichment for nucleated erythrocytes, using an anti-CD71 (transferrin receptor) monoclonal antibody. To discriminate between fetal nucleated erythrocytes and those of maternal origin, enriched fractions were simultaneously stained with an anti-fetal haemoglobin (HbF) antibody and hybridized with probes specific for X and Y chromosomes. Samples were then subjected to blind analysis along with negative control samples from non-pregnant volunteers. Using this dual analysis, we were able to determine that less than one nucleated erythrocyte per ml of maternal blood was of fetal origin. Small numbers of these fetal cells were found in 87.5% of pregnancies, ranging from 6 to 35 weeks gestational age. Comparison of HbF and X/Y probe data also suggests that the fetal cells are less suitable for fluorescence in-situ hybridization (FISH) analysis than similar preparations from other sources.

Nucleated erythrocytes in maternal blood: quantity and quality of fetal cells in enriched populations

Nucleated erythrocytes in maternal blood: quantity and quality of fetal cells in enriched populations

Erythroid-specific antibodies enhance detection of fetal nucleated erythrocytes in maternal blood.

Fetal nucleated erythrocytes (NRBC) in maternal blood are a non-invasive source of fetal DNA for prenatal genetic screening. We compared the effectiveness of three monoclonal antibodies for the separation of fetal cells from maternal blood by flow sorting. Mononuclear blood cells from 49 healthy pregnant women were incubated with antibody to CD 71, CD 36, and/or glycophorin A (GPA), employed singly or in combination with each other. These monoclonal antibodies recognize surface antigens on haematopoietic precursor cells. Successful isolation of fetal cells was defined as detection of Y chromosomal sequences in maternal blood from women carrying male fetuses, with absence of Y sequences when female fetuses were carried. Thus, gender prediction accuracy was used as a measure of fetal cell separation. Using anti-CD 71 to isolate fetal cells, gender prediction was 57 per cent correct; with anti-CD 36, it was 88 per cent correct. Anti-GPA, an erythrocyte-specific antigen, used alone or in combination with anti-CD 71 or 36, improved gender prediction to 100 per cent. We conclude that antibody to GPA improves the retrieval of fetal NRBC from maternal blood, permitting genetic analysis by the polymerase chain reaction.

Possible effect of gestational age on the detection of fetal nucleated erythrocytes in maternal blood

Maternal venous blood samples, obtained from six pregnant women, were used as a source of fetal nucleated erythrocytes (NRBC). Fetal cell enrichment was potentiated by flow sorting with the monoclonal antibodies TfR, Leu-4, and Leu-M3. Single copy Y chromosomal DNA sequences were detected in samples obtained from two women at 11 and 12 weeks' gestation. Y DNA sequences were absent in a subsequent sample from one of these women at 19 weeks and in two other women at 16 and 20 weeks. All four women delivered males. Y DNA sequences were not detected in two women who delivered females. By combining these results with prior data on the detection of Y chromosomal DNA sequences in maternal blood from male-bearing pregnancies, a relationship between gestational age and feto-maternal transfer of NRBC is suggested.

Isolation of fetal DNA from nucleated erythrocytes in maternal blood.

Fetal nucleated cells within maternal blood represent a potential source of fetal genes obtainable by venipuncture. We used monoclonal antibody against the transferrin receptor (TfR) to identify nucleated erythrocytes in the peripheral blood of pregnant women. Candidate fetal cells from 19 pregnancies were isolated by flow sorting at 12 1/2-17 weeks gestation. The DNA in these cells was amplified for a 222-base-pair (bp) sequence present on the short arm of the Y chromosome as proof that the cells were derived from the fetus. The amplified DNA was compared with standardized DNA concentrations; 0.1-1 ng of fetal DNA was obtained in the 20-ml maternal samples. In 7/19 cases, a 222-bp band of amplified DNA was detected, consistent with the presence of male DNA in the isolated cells; 6/7 of these were confirmed as male pregnancies by karyotyping amniocytes. In the case of the female fetus, DNA prepared from samples at 32 weeks of gestation and cord blood at delivery also showed the presence of the Y chromosomal sequence, suggesting Y sequence mosaicism or translocation. In 10/12 cases where the 222-bp band was absent, the fetuses were female. Thus, we were successful in detecting the Y chromosomal sequence in 75% of the male-bearing pregnancies, demonstrating that it is possible to isolate fetal gene sequences from cells in maternal blood. Further refinement in methodology should increase sensitivity and facilitate noninvasive screening for fetal gene mutations.

Significance of Transplacental Hemorrhage in the Induction of Specific Maternal Unresponsiveness&lt;xref ref-type="fn" rid="FN2"&gt;2&lt;/xref&gt;

Transplacental hemorrhage is reportedly detectable by erythrocytes containing fetal hemoglobin-F in the maternal circulation. The procedure in the present study is based on the premise that fetal hemoglobin is not eluted from red cells in blood smears by an acid buffer, whereas adult hemoglobin is removed. Erythrocytes containing hemoglobin-F were observed in blood smears of both virgin and pregnant BALB/c mice, but the relative number of these cells in the maternal blood increased during pregnancy, reached a peak around the time of parturition, and decreased thereafter. In BALB/c females pregnant by DBA/2 males, the relatively large numbers of acid-resistant erythrocytes in maternal blood were related to the maternal unresponsiveness to DBA/2 allografts. The fetal derivation of at least a fraction of these cells was suggested by the apparent activity of fetal immunogens in the maternal circulation. The blood of peripartum BALB/c mice multiparous by DBA/2 males was injected into normal, nonimmune BALB/c mice. The blood recipients were later challenged with an allotransplantable DBA/2 tumor. A low degree of immunity was indicated by a decreased size of tumor implants. Attempts to demonstrate vertical transmission of immune suppression from mothers to progeny were negative. These findings indicate that transplacental hemorrhage is a potential source of antigens involved in the induction of specific maternal unresponsiveness.

The quantitative estimation of foetal erythrocytes in maternal blood.

Abstract. The number of foetal erythrocytes in maternal blood is determined by adding yeast cells to the sample before preparation of the smear, extraction and staining. 25–1100 foetal erythrocytes per μ1 blood, corresponding to a foeto‐maternal transfusion of about 20–900 μ1 are recovered with an average coefficient of variation of 20%. The clinical application of the method is demonstrated by following the rate of disappearance of the foetal erythrocytes from the maternal blood after a foetomaternal transfusion.

MECHANISMS OF ISOIMMUNIZATION. I. THE TRANSPLACENTAL PASSAGE OF FETAL ERYTHROCYTES IN HOMOSPECIFIC PREGNANCIES

A critical evaluation and discussion of certain technical aspects of the acid elution method and the immunofluorescent technic for the demonstration of fetal erythrocytes in maternal blood is presented. With appropriate precautions a close agreement between the two methods was obtained. Using one or both methods as applicable, base line data concerning transplacental passage were obtained in 622 unselected women, compatible with their offspring in the ABO system and not sensitized against the Rh factor. The intermittent entry of fetal erythrocytes into the maternal blood in small quantities was found to be a physiologic event. Postpartum, fetal erythrocytes were demonstrated in 50 per cent of the mothers. In approximately 10 per cent of the series, large fetal losses estimated to range from 0.5 to 40 ml. were observed. Massive transplacental hemorrhage was detected in nearly 1 per cent of the cases by examination of the maternal blood and usually but not always by overt anemia in the fetus. It was found to be the cause of stillbirth in one case. The evidence suggested that fetal bleeds usually began well before the onset of labor. Though labor itself under pathologic circumstances may be associated with transplacental hemorrhage, under ordinary conditions it was found to be of little or no significance with regard to the entry of fetal erythrocytes into the maternal circulation. Survival of fetal erythrocytes in the maternal circulation after delivery was generally found to correspond to the expected life span of red corpuscles. Apparent shortening of survival observed in several instances was probably due to the occurrence of the original spill some time before delivery. In two instances persistence of fetal erythrocytes well beyond the normal life span was observed. Both cases involved massive transplacental hemorrhage and fetal anemia with marked erythroblastemia, and mother and child were compatible to an exceptional degree with respect to blood group factors. The findings suggested the successful transplant of replicable erythroid precursor cells from fetus to mother with prolonged maternal tolerance, an interpretation supported by the results of skin homografts from offspring to mother in one case. The implications of these findings are discussed.