Detection of fetomaternal hemorrhage

The prevention of Rhesus D alloimmunization through Rh immune globulin (RhIg) administration is the major indication for the accurate detection and quantification of fetomaternal hemorrhage (FMH). In the setting of D incompatibility, D-positive fetal cells can sensitize the D-negative mother, resulting in maternal anti-D alloantibody production. These anti-D alloantibodies may lead to undesirable sequelae such as hemolytic disease of the newborn (HDN). Since the widespread adoption of FMH screening and RhIg immunoprophylaxis, the overall risk of Rh alloimmunization and infant mortality from HDN has substantially decreased. The rosette screen, the initial test of choice, is highly sensitive in qualitatively detecting 10 mL of fetal whole blood in the maternal circulation. As the screen is reliant on the presence of the D antigen to distinguish fetal from maternal cells, it cannot be used to detect FMH in D-positive mothers or in D-negative mothers carrying a D-negative fetus. The Kleihauer-Betke acid-elution test, the most widely used confirmatory test for quantifying FMH, relies on the principle that fetal RBCs contain mostly fetal hemoglobin (HbF), which is resistant to acid-elution whereas adult hemoglobin is acid-sensitive. Although the Kleihauer-Betke test is inexpensive and requires no special equipment, it lacks standardization and precision, and may not be accurate in conditions with elevated F-cells. Anti-HbF flow cytometry is a promising alternative, although its use is limited by equipment and staffing costs. Hematology analyzers with flow cytometry capabilities may be adapted for fetal cell detection, thus giving clinical laboratories a potentially attractive automated alternative for quantifying FMH.

The assessment of feto-maternal hemorrhage in an artificial model using anti-D and anti-fetal hemoglobin antibody by flow cytometry

BACKGROUND

When fetal red cells enter the maternal circulation from placenta, an event would be happened that is described as feto-maternal hemorrhage (FMH). This life-threatening condition could be detected by using RBC antigens (surface antigens and intracellular antigens). Therefore, the measurement of fetal RBC in an artificial model would be useful to calculate FMH and consequently the dosage of Rhogam for prophylaxis. The aim of the present study was to evaluate FMH in an artificial mixture model.

METHODS

A series of 40 artificial specimens were prepared consisting of Rh(D) negative adult blood (non-immunized) spiked with varying amounts of Rh(D) positive cord blood from mothers between 20-30 years old in Shahid Beheshti Hospital, Tehran, Iran. Monoclonal anti-D and anti-HbF (fetal hemoglobin) were used for detection of fetal RBC in artificial mixture sample modeling.

RESULTS

This study showed that the percentage of fetal cells in artificial sample for anti-D antigen is in ranges of 0.28%-0.32% for a 0.25% dilution mixture, and 1.3%-2.05% for the mixture with dilution 2%. In addition, the ranges of data for anti-HbF staining was obtained 0.2%-0.34% for the 0.25% dilution sample, and the ranges of 1.04-1.8% for the 2% dilution. The regression analysis indicated that the correlation of anti-D assessment with expected standard method was r2 = 0.9672 and anti-HbF assessment was r2 = 0.8842.

CONCLUSION

Although both molecule targets could be used for detection of fetal RBC, in this model, anti-D staining was more accurate than anti-HbF staining. However, since anti-D can not be utilized for low-density or weak phenotype and other incompatibility, the anti-HbF labeling could be used for all FMH.

Detecting fetomaternal hemorrhage by flow cytometry

PURPOSE OF REVIEW

The aim of this review is to summarize the most recent developments in the area of detection of fetomaternal hemorrhage by flow cytometry.

RECENT FINDINGS

Maternal red blood cell chimerism is readily detectable by flow cytometry. Fetal and maternal red blood cells differ in their content of fetal hemoglobin (alpha2gamma2). Fetal red blood cells contain fetal hemoglobin, and normal maternal red blood cells contain some percentage of fetal hemoglobin in a background of normal adult hemoglobin. All blood group systems with allelic differences between mother and fetus are readily applicable for detection of fetomaternal hemorrhage by fetal hemoglobin.

SUMMARY

Fetal hemoglobin for detection of fetomaternal hemorrhage is an accurate clinical diagnostic procedure for investigation of anemia in fetus and newborn.

Evaluation of various methods of maternal placental blood collection for immunology studies

The collection of maternal placental intervillous blood (IVB), without contamination of fetal blood and with an accurate mononuclear cell profile, is essential for immunological studies of placental malaria and other infectious diseases of the placenta. We have compared five documented methods of IVB collection: perfusion, incision, biopsy, tissue grinding, and puncture (prick) for fetal blood contamination and mononuclear cell profiles using flow cytometry. Twenty-five placentas were obtained from Plasmodium falciparum and human immunodeficiency virus-negative primigravid and secundigravid women delivering at Nyanza Provincial Hospital in Kisumu, western Kenya. Each of the five methods was performed on the same placenta. Fetal red blood cell contamination was significantly lower for the prick and perfusion methods (4.1% and 8.3%, respectively) than for incision (59.5%), biopsy (42.6%), and tissue grinding (19.9%). Significant variation was noted among the five methods in the percentages of monocytes, total T cells, CD4+ and CD8+ T cells, B cells, and NK cells. Further, a pairwise comparison of prick and perfusion, the two methods with low fetal blood contamination, showed that they were not different for fetal red blood cell contamination levels; however, prick yielded significantly higher percentages of CD4 T cells and CD4 memory T cells than perfusion. Collection by prick was determined to be the best method of intervillous blood collection for immunology studies, and perfusion represented the next best method of choice due to high sample volume yield. Overall, in considering the advantages/disadvantages of the two methods with low fetal cell contamination, we conclude that a combination of prick and perfusion is most suitable for immunology studies.

Analysis of interaction of cloned human and/or sheep fetal hemoglobin γ-chain and LPS in augmenting induction of inflammatory cytokine production in vivo and in vitro

We have reported earlier that purified preparations of sheep fetal hemoglobin, but not adult hemoglobin, in concert with non-stimulatory doses of lipopolysaccharide (LPS) (lipid A), act cooperatively to regulate in vitro production of a number of cytokines, including TNFalpha, TGFbeta and IL-6 from murine and human leukocytes. Following in vivo treatment of mice with the same combination of hemoglobin and LPS, harvested spleen or peritoneal cells showed a similar augmented capacity to release these cytokines into culture supernatants. We report below that genetically cloned gamma-chain of human or sheep fetal hemoglobin, but not cloned alpha- or beta-chains, can produce this cooperative effect, as indeed can HPLC purified, heme-free, gamma-chains derived from cord blood fetal hemoglobin, and that purified haptoglobin completely abolishes the cooperative interaction.

Isolation of epsilon-haemoglobin-chain positive fetal cells with micromanipulation for prenatal diagnosis

OBJECTIVES

The isolation and analysis of fetal cells in maternal blood during pregnancy is under investigation as a means of noninvasive prenatal diagnosis. The aim of our study was to detect fetal gender from maternal peripherial blood samples during pregnancy with the detection and analysis of epsilon-haemoglobin-chain positive fetal nucleated red blood cells (NRBCs) collected by a micromanipulator. Here we report our first results.

DESIGN AND METHODS

We obtained maternal blood from 14 singleton pregnancies. After a double density gradient separation, magnetic activated cell sorting was performed by positive selection for nucleated red blood cells with anti-CD71. With the help of this enrichment step, followed by immunophenotyping with an anti-haemoglobin-epsilon monoclonal antibody, the isolation of the epsilon haemoglobin chain positive cells with micromanipulation could be done. We performed single cell fluorescent PCR analysis of these cells; we used primers for the amelogenin gene to detect fetal gender. We compared our findings with the results of amniocentesis.

RESULTS

Fetal gender was successfully determined in 11 out of 14 cases; among them, in 2 cases with Klinefelter syndrome (47,XXY).

CONCLUSION

The results of our study suggest that micromanipulation and QF-PCR analysis of anti-haemoglobin-epsilon fluorescent antibody stained fetal cells from maternal blood can be useful in prenatal diagnosis to detect fetal gender and promising to be improved to detect chromosomal abnormalities.

Massive antenatal fetomaternal hemorrhage: evidence for long-term survival of fetal red blood cells

BACKGROUND

Massive fetomaternal hemorrhage (FMH) can lead to life-threatening anemia. Quantification based on flow cytometry with anti-hemoglobin F (HbF) is applicable in all cases but underestimation of large fetal bleeds has been reported. A large FMH from an ABO-compatible fetus allows an estimation of the life span of fetal red blood cells (RBCs) in the maternal circulation.

CASE REPORT

The mother went to the obstetrician twice antepartum owing to symptoms assumed to be preeclampsia; that, however, was not found. She later delivered by cesarean section owing to diminished fetal movements. No fetal weight gain was observed during the last 2 weeks of pregnancy.

STUDY DESIGN AND METHODS

Fetal RBCs were quantified by flow cytometry with anti-HbF, anti-Fy(a), anti-s, and anti-Jk(b) on a regular basis.

RESULTS

The infant had anemia at delivery and an FMH was determined to be 314 +/- 17 mL (+/- SD) of whole blood. It is assumed that the two antenatal visits were associated with the FMH. Postpartum follow-up showed that fetal RBCs in the maternal circulation were detectable with anti-HbF up to 119 days. Quantification by flow cytometry based on anti-HbF was in agreement with quantification based on anti-Fy(a), anti-s, and anti-Jk(b), although they were less sensitive.

CONCLUSION

ABO-compatible fetal RBCs from an FMH had a life span in the maternal circulation close to that of adult RBCs.

[DMDUse of fetal specific antibody-HbF to detect fetal erythroblasts for non-invasive prenatal diagnosis of DMD]

Maternal blood was obtained at 8-26 weeks of gestation. After discontinuous density gradient centrifugation with Percoll, HbF antibody was used to identify fetal NRBC. The precise differentiation between fetal and maternal NRBC is based on the constitutional difference between fetal and adult hemoglobin (Hb). Fetal cells appear yellow cytoplasmic staining,while adult cells colorless. NRBCs were collected by micromanipulation and whole genome amplification was performed. DMD was prenatally diagnosed by using the combination of sex determination,multiplex PCR and linkage analysis of several STR sites of dystrophin. NRBCs stained with HbF were found in all of 20 maternal blood samples with gestations, and 7 fetuses with risk of DMD were diagnosed. We concluded that HbF antibody could identify fetal NRBC efficaciously, and this is a kind of more prospective application method.

[Use of specific antibody to detect fetal erythroblasts in maternal circulation]

OBJECTIVE

To investigate the feasibility of using immunohistochemical technique to detect the presence of fetal erythroblasts in the maternal circulation for prenatal diagnosis.

METHODS

Maternal blood was obtained from 30 pregnant women at 8 to 26 weeks of gestation. Nucleated red blood cells (NRBCs) were separated with Percoll using a discontinuous density gradient method, and then smeared on microscope slides using cytocentrifugation. Slides were stained with antibody against the gamma-chain of fetal hemoglobin (HbF). All positive NRBCs were collected by micromanipulator under microscopic observation, and then amplified by improved primer extension preamplification(PEP). Sex and Duchenne's musclar dystrophy (DMD) genetic diagnosis were determined from a small aliquot of the PEP reaction.

RESULTS

NRBCs stained with HbF were found in all of the blood from the 30 pregnant women at 8 to 26 weeks of gestation. 17 male fetuses and 13 female fetuses were detected in the 30 cases. These results coincided with those of induced labor or amniotic fluid control, and 8 fetuses at the risk of DMD were diagnosed.

CONCLUSION

This diagnostic method using immunohistochemical technique to mark fetal NRBC shows good application prospects.

Production of murine monoclonal antibody to fetal hemoglobin

Fetal hemoglobin (Hb F) is a major hemoglobin (Hb) component at birth. Hb F levels are markedly elevated in a number of inherited and acquired disorders. Measurement of Hb F levels is usually carried out by alkali denaturation which is not very accurate for low and high values. An accurate estimation of Hb F, and also of F cells, is desired in many hematological disorders like sickle cell disease, in monitoring the efficacy of hydroxyurea (HU) therapy, to assess feto-maternal hemorrhage (FMH) during pregnancy and in the postpartum period. We have raised a murine monoclonal antibody to human Hb F, that accurately measures the number of F cells by flow cytometry. The antibody was found to be potent and specific for F cells.

False positive Kleihauer tests and unnecessary administration of anti-D immunoglobulin

This obstetric case shows two false negative Kleihauer tests and two persistently positive Kleihauer tests leading to unnecessary administration of anti-D immunoglobulin. A diagnosis of hereditary persistence foetal haemoglobin (HPFH) was only confirmed by access to flow cytometry making use of both anti-HbF and anti-D labels. The case highlights the importance of a high index of clinical suspicion for HPFH and the importance of access to flow cytometry estimation of minor RhD red cell populations postnatally in RhD-negative mothers.

Studies on the isolation and identification of fetal nucleated red blood cells in the circulation of pregnant women before and after chorion villus sampling

OBJECTIVE

To investigate the feasibility of various molecular forms of hemoglobin as markers for fetal nucleated red blood cells (NRBCs).

METHODS

The presence of epsilon and gamma globin positive NRBCs was investigated in pure fetal blood and in blood from pregnant women before and after chorion biopsy. Maternal samples were enriched for NRBCs by various conventional methods, including limited enrichment by only positive CD71 selection or single density gradient. We searched for fetal cells on slides by automated scanning. Fetal cells were defined by (1) the presence of epsilon or gamma globin and (2) simultaneously by the presence of a Y chromosome signal.

RESULTS

18 of 25 gamma globin positive cells identified in blood samples after chorion biopsy were chromosome Y signal positive, and 1 cell had two X chromosome signals. 263 of 339 epsilon globin positive cells identified in blood samples after chorion biopsy were hybridized with X and Y chromosome probes. None had two X signals, and 249 were Y positive. In blood samples before chorion biopsy, only 1 epsilon globin positive fetal NRBC and no epsilon globin positive maternal NRBCs were found.

CONCLUSIONS

Epsilon globin may be specific for fetal NRBCs. Only 1 epsilon globin positive fetal cell was identified in 1 of 12 blood samples before chorion biopsy, representing a total of 182 ml of maternal blood. This suggests that most fetal cells found in maternal blood by fluorescence in situ hybridization methods may not be NRBCs.

Identification of fetal nucleated red blood cells in the maternal circulation during pregnancy using anti-hemoglobin-epsilon antibody

AIM

To investigate the use of anti-hemoglobin-epsilon antibody in order to identify fetal cells in the maternal circulation during pregnancy.

MATERIALS AND METHODS

48 blood samples were obtained from pregnant women, 26 in the 1st trimester and 22 in the 2nd trimester. Magnetic activated cell sorting was used for fetal cell enrichment followed by immunophenotyping with a monoclonal antibody against hemoglobin-epsilon. FISH with X, Y and 21 chromosome-specific probes was performed in 29 cases.

RESULTS

The mean number of epsilon-positive cells was 9.2 (range 2-23) in the 1st trimester, 4.8 (range 3-13) in the 2nd trimester and 22 (range 15-28) in pregnancies with Down syndrome. No significant difference was noted in the number of epsilon-positive nucleated red blood cells (NRBCs) isolated from carriers and noncarriers of beta-thalassemia. FISH analysis was successful in 24 cases. In 4 cases with known male fetuses, an average of 4.7 epsilon-positive cells showed a Y signal. In 4 cases with Down syndrome, all epsilon-positive cells showed 3 signals for chromosome 21.

CONCLUSION

Anti-hemoglobin-epsilon antibody has increased specificity for fetal NRBCs and should be preferentially used to improve noninvasive prenatal diagnosis of chromosome abnormalities from fetal cells in maternal blood.

Quantification of feto-maternal haemorrhage (FMH) by flow cytometry: anti-fetal haemoglobin labelling potentially underestimates massive FMH in comparison to labelling with anti-D

Many centres now routinely use flow cytometry to quantify feto-maternal haemorrhage (FMH). However, which flow cytometric method is the most accurate in quantifying FMH is currently unknown. An audit of clinical results in which FMH had been estimated by both directly conjugated monoclonal anti-D and anti-fetal haemoglobin (HbF) labelling suggested that the anti-HbF labelling method may underestimate massive FMH in comparison to labelling with anti-D. Subsequent to this audit, 46 samples of adult D-negative blood were spiked with varying amounts of D-positive cord blood (0.05-10% fetal cells per sample), and the number of fetal cells present was quantified by both labelling methods. The percentage of fetal cells detected by anti-D was not significantly different to the estimated percentage of fetal cells added to each sample (P = 0.636). However, anti-HbF labelling significantly underestimated the percentage of fetal cells present (P = 0.0001). In comparison to anti-D, the percentage of fetal cells detected by anti-HbF was also significantly lower (P < 0.0001). The difference in fetal cell detection between anti-D and anti-HbF labelling was only apparent in the spiked samples containing > or =1% fetal cells per sample. In samples containing < or =0.6% fetal cells, no significant difference in the detection of fetal cells between anti-D and anti-HbF labelling was observed (P = 0.11). To allow adequate immunoprophylaxis in D-negative mothers with massive FMH, we recommend that anti-D labelling should be used in the routine flow cytometric estimation of FMH.

Evaluation of flow cytometric enumeration of foetal erythrocytes in maternal blood

In pregnant women subject to abdominal trauma or other foetomaternal haemorrhage, foetal red blood cells containing haemoglobin-F (HbF) can be found in the circulation. Recently, a monoclonal antibody to HbF has become commercially available, enabling application of a flow cytometric immunofluorescence method for accurately determining the concentration of HbF+ red blood cells. We demonstrate that white blood cells are included in the cluster selected as red blood cells and that these white blood cells exhibit a level of autofluorescence that coincides with the fluorescence signal from HbF+ red blood cells. However, these white blood cells can be excluded from the analysis, thus preventing spuriously increased HbF+ red blood cell counts. We present the results of patient samples containing HbF+ red cells as illustrations of the technique and as a potential interference by HbF-containing cells of nonfoetal origin. Using samples spiked with cord blood, the method is exactly linear with a high coefficient of correlation (r=0.997). Furthermore, the assay has excellent precision (CV < 2.4%), a low limit of detection (0.12% HbF+ RBC), is independent of Rhesus D and can be completed within 1.5 h. This method is suitable for accurate determination of foetomaternal haemorrhage.

Quantification of foetomaternal haemorrhage. An analysis of two cytometric techniques and a semiquantitative gel agglutination test

Traditional tests to screen for foetomaternal haemorrhage are time-consuming and difficult to perform. The Kleihauer test is widely used but difficult to standardize. We evaluated three techniques for quantifying foetomaternal haemorrhage: a semiquantitative gel agglutination test and two flow cytometric techniques. The gel agglutination test is based on the consumption of anti-D reagent by D+ cells, analysing the reaction of the supernatant against indicator cells in a Coombs-gel card. In the two colour direct immunofluorescent technique, the sample is incubated with Per-CP labelled anti CD45 antibody, fixed with glutaraldehyde and permeabilized by exposure to Triton X-100. An aliquot is stained with an antibody to foetal haemoglobin, conjugated with fluorescein isothiocyanate or phycoerythrin. The indirect immunofluorescent technique is based on the labelling of Rh (D) antigen with an anti D reagent, followed by the addition of an anti IgG antibody conjugated with phycoerythrin. Foetomaternal haemorrhage was not detected in 75 of the 85 samples analysed by the direct immunofluorescent technique. In the remaining 10 samples, the volume was very low. Thirty-five samples with Rh (D) antigen incompatibility were analysed in parallel by the indirect immunofluorescent technique and in 15 of the 35 samples, the gel agglutination technique was also carried out. The three techniques gave similar results. The gel agglutination test can be used to screen for foetomaternal haemorrhage, while greater volumes should be quantified by flow cytometric techniques.

A new anti-hemoglobin F antibody against synthetic peptides for the detection of F-cell precursors (F-blasts) in bone marrow

To date there are few antibodies available for the detection of fetal hemoglobin (HbF)-containing erythroblasts (F-blasts) in paraffin-embedded hematopoietic tissues. Recently, we developed a new polyclonal antibody specific to F-blasts by immunization of a rabbit with synthetic peptides of human HbF. Specificity and reactivity of the antibody were confirmed by enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry. ELISA confirmed that the antibody showed strong immunoreactivity to fetal hemoglobin but no reaction to adult hemoglobin. The antibody could detect the presence of fetal blood hemolysates (10 microg/mL) at a dilution of 10(-5). According to immunohistochemical analysis, there were strong positive reactions to fetal erythroblasts in the liver and the spleen at 29 weeks of gestation and to erythroblasts from patients with myelodysplastic syndromes and erythroleukemia but no reactions to normal adult erythroblasts in bone marrow. Fetal erythrocytes in fetal blood vessels of placental tissues were strictly distinguished from maternal erythrocytes in the same sections by their positive reactions, indicating the presence of HbF. This new antibody will be a useful tool for studying fetal hemoglobin synthesis and for detecting F-blasts in archival specimens of various hematological diseases.

Embryonic and fetal globins are expressed in adult erythroid progenitor cells and in erythroid cell cultures

The understanding of human hemoglobin ontogeny during development is of biological and clinical importance. Molecular and immunocytological techniques were used to study the expression of embryonic zeta (zeta), epsilon (epsilon), and fetal gamma (gamma) globin genes in newborn cord blood, peripheral blood from men, pregnant and non-pregnant women, and in vitro mononuclear cell cultures. We have shown that embryonic and fetal globin mRNA and peptides are expressed in cultured erythroid cells and in circulating blood cells from newborns, adult non-pregnant women and from men. The findings suggest that during erythroid cell differentiation in newborns and adults, there is a transient recapitulation of sequential globin chain expression as found during embryonic and fetal development. Furthermore, these findings underscore the need for caution in using embryonic and fetal globin chains as markers to identify erythroid cells of fetal origin in maternal circulation for prenatal diagnosis.

Genetic analysis of fetal nucleated red blood cells from CVS washings

Chorionic villus sampling (CVS) is an established invasive prenatal diagnostic method for the detection of fetal chromosome aberrations. In 1-2% the karyotype result of CVS is inconclusive and follow-up confirmation will be required. To avoid another invasive procedure we examined fetal nucleated red blood cells (NRBCs) from CVS washings for genetic analysis. We analysed the washings of 20 chorionic villi samples of male fetuses. Fetal NRBCs were immunostained by an antibody against embryonic haemoglobin (HbE). FISH was performed with probes specific for the X and Y chromosome and the nucleus was counterstained with DAPI. Cells positive for the antibody, as well as for DAPI, were collected and stored by a semi-automated microscope. An operator reviewed those cells for their FISH signals. In 19 out of 20 CVS washings we found nucleated cells positive for HbE together with XY FISH signals. In none of the washings HbE positive cells with two X signals were found. Our results indicate that anti-HbE is a very specific antibody for identifying fetal NRBCs. NRBCs from CVS washings can be used as an additional fetal tissue for first trimester prenatal diagnosis.

Non-invasive exclusion of fetal aneuploidy in an at-risk couple with a balanced translocation

A pregnant woman who was a carrier for a balanced chromosome translocation [46,XX, t(1;6) (p31;q14)] and who had had six miscarriages, declined invasive testing but agreed to non-invasive prenatal diagnosis by analysis of fetal cells in maternal blood. Monoclonal antibody (Mab) against the zeta (z) and gamma (gamma) chains of embryonic and fetal haemoglobin were used to identify fetal nucleated erythrocytes (FNRBC). There were no FNRBC detected at 7 weeks, one anti-z-positive FNRBC was detected at 11 weeks, and 12 anti-gamma-positive FNRBC were detected at 20 weeks. Fluorescent in-situ hybridization was performed using probes for chromosomes X, Y, 1 and 6 to identify fetal gender and the presence of an unbalanced chromosomal translocation. A tentative prenatal diagnosis was made of a female fetus disomic for chromosomes 1 and 6. A female infant with a 46,XX karyotype was born at term. This is the first attempt of exclusion of a chromosome translocation using fetal cells isolated from maternal blood. There is an advantage of using fetal cells isolated from maternal blood for non-invasive prenatal diagnosis in couples who have a history of multiple miscarriages due to a parental translocation, and who decline invasive testing in a pregnancy that continues to the second trimester.

Preeclampsia-associated hepatic hemorrhage and rupture: mode of management related to maternal and perinatal outcome

This article is a critical review of the obstetric literature concerning preeclampsia-associated hepatic hemorrhage to develop guidelines conducive to optimal maternal and perinatal outcomes. An English literature search was performed for reports of hepatic hemorrhage or hepatic rupture in pregnancy during 1960 to 1997. Data were analyzed by Statmost packages using ANOVA, Chi-square, and Fisher's exact tests. One hundred forty-one patients with hepatic rupture/hemorrhage were reported. The three most common presenting findings were epigastric pain, hypertension, and shock. With rare exception, patients had evidence of preeclampsia. Diagnosis was elusive and most frequently accomplished at laparotomy. When utilized, ultrasound and computed tomography (CT) were helpful diagnostic modalities. Maternal survival was highest in the arterial embolization treatment group. Maternal and perinatal survival improved considerably during the study interval. Route of delivery did not seem to impact survival rates. It was concluded that the application of ultrasound and CT for diagnosis and the use of hepatic artery embolization for treatment of hepatic hemorrhage/rupture seem to be beneficial management options for this rare event.

Detection of hemoglobin variants in erythrocytes by flow cytometry

BACKGROUND

With the emergence of fetal hemoglobin (Hb F)stimulating agents as potential treatments for sickle-cell disease and thalassemias, procedures to monitor the effect of these agents on Hb F levels in individuals will be needed. We developed a rapid procedure that detects fetal hemoglobin in erythrocytes (F cells) using a fluorescein isothiocyanate (FITC) conjugated monoclonal antibody against Hb F.

METHODS

Ten microliters of washed blood was fixed in formaldehyde and glutaraldehyde, then permeabilized in a Triton X-100/PBS solution containing a FITC-labeled monoclonal antibody to Hb F. The blood was analyzed by flow cytometry to determine the percentage of F cells.

RESULTS

Nearly 200 Hb F-containing samples were analyzed by this protocol and demonstrated good correlation to percent Hb F results determined by high pressure liquid chromatography (HPLC). In addition, a number of samples were fixed and permeabilized using this method as well as a previously-described method that uses dimethyl 3,3'dithiobispropionimadate (DTBP) as a fixative as well as a different anti-Hb F monoclonal. Good correlation (r = 0.96, r2 = 0.93, P<0.001) was observed between the two protocols.

CONCLUSIONS

This procedure is easy, reproducible, and gives accurate F cell results. It can be used to measure a wide range of F cell percentages and may also be used to dual-stain Hb F along with other hemoglobin variants and erythrocyte surface antigens.

Determination of Hb F levels: the routine methods

The two classical methods used to determine the level of Hb F in a hemolysate are herein described. Measurement of this hemoglobin fraction by resistance to alkali denaturation was the first technique introduced; it is today largely replaced by ion exchange high performance liquid chromatography. The limits, pitfalls, and advantages of the two methods are discussed.

F reticulocytes assay: a method to evaluate fetal hemoglobin production

Production of fetal hemoglobin (Hb F) involves molecular as well as cellular aspects as, among red blood cells, it is restricted to a specific population referred as the F cells. Thus understanding the mechanisms involved in persistence or re-emergence of Hb F production in various inherited or acquired conditions requires the measurement of both Hb F and F cells. In addition, in disorders with a hemolytic component, including sickle cell disease (SCD), because of a probable preferential survival of F cells as compared to non-F cells, the true parameter of F cell production is the F reticulocyte count. The F cells/F reticulocytes ratio then selectively reflects this preferential survival. Here we describe an original immunofluorescence microscopy assay that permits the simultaneous measurement of F cells and F reticulocytes. For this assay to be widely usable, we chose to use commercially available monoclonal antibodies.

Techniques for studying stimulation of fetal hemoglobin production in human erythroid cultures

This report describes in detail the procedures for growing human erythroid cells in liquid culture for evaluating the potential of pharmacological agents to affect hemoglobin production. The procedure consists of two phases: an erythropoietin-independent phase in which peripheral blood mononuclear cells are first cultured in the presence of a combination of hemopoietic growth factors, but in the absence of erythropoietin, where early erythroid committed progenitors proliferate and differentiate into more mature progenitors. In the second phase, the latter cells, cultured in an erythropoietin-supplemented medium, continue to proliferate and mature into orthochromatic normoblasts and enucleated erythrocytes. This procedure produces large cultures of relatively pure and synchronized erythroid cell populations derived from normal donors or patients with beta hemoglobinopathies. The cultured cells recapitulate many aspects of erythropoiesis in vivo, including the donor's pattern of hemoglobin production (types and proportions). Tested compounds, at different concentrations, are added at different stages of the culture. The various types of hemoglobins and globin chains produced can be measured by high performance liquid chromatographic techniques and their cellular distribution analyzed by flow cytometry using fluorescently labeled antibodies against specific hemoglobins. This approach provides a screening system for compounds with potential therapeutic efficacy in patients with beta hemoglobinopathies.

Gamma chain heterogeneity: determination of Hb F composition by perfusion chromatography

The Ggamma:Agamma ratio is around 70:30 at the time of birth and usually 40:60 in the trace amounts of Hb F found in the adult. Changes in this ratio are observed in several hemoglobin disorders providing insights on the genetics and molecular pathophysiology of these diseases. Several techniques have been proposed to measure the Ggamma:Agamma ratio. We here describe perfusion chromatography which is now in routine use in one of our laboratories. The method involves a high velocity flow of the mobile phase through a porous reversed phase chromatographic stationary bed and allows us to determine this parameter one order of magnitude faster than with conventional high performance liquid chromatography.

Cross evaluation of three flow cytometric F cell counting methods performed by different laboratories

Three flow cytometric methods of counting F cells were evaluated in the settings of an external laboratory assessment scheme. The laboratories to participate with a different method were located in Oxford (method O), Athens (method A) and Jerusalem, (method J). Two monoclonal anti-gamma chain antibodies were used: monoclonal antibody produced by P. Beverley (Oxford) (BEV) and an antibody provided by Bioatlantic S.A.R.L. (France) (BIO). The specimens tested were mixtures in five predefined ratios of a sample with homozygous deltabeta-thalassemia with 100% F cells with a sample with no F cells. A central independent laboratory prepared and distributed the aliquots (at room temperature) to the participating centers within 2 (O), 3 (A), and 6 (J) days. The performance of the three methods was evaluated by: 1) deviation indices, 2) relative accuracy, as percent difference of the counts from the target values, and 3) bias and linearity by linear regression of the counts versus the target values [parameters: slope (s), y-intercept (y), R squared (Rs), and F ratio]. The highest score of performance was obtained by method A with both monoclonal antibodies.

Detection of fetal red cells in fetomaternal hemorrhage using a fetal hemoglobin monoclonal antibody by flow cytometry

BACKGROUND

The laboratory determination of the level of fetal cells in maternal circulation remains an important support in the obstetrical management of women with suspected uterine trauma and in the proper dose administration of anti-D for prevention of Rh hemolytic disease of the newborn. Limitations in the sensitivity and precision of the widely used manual Kleihauer-Betke test have prompted an increased utilization of flow cytometric methods for fetal cell detection in maternal blood samples.

STUDY DESIGN AND METHODS

Murine monoclonal antibodies directed against fetal hemoglobin (HbF) were developed, conjugated to fluorescein isothiocyanate, and used in a multiparametric flow cytometric assay developed for the quantitation of fetal red cells. A rapid intracellular staining method using brief glutaraldehyde fixation and Triton X-100 permeabilization prior to monoclonal antibody incubation was developed, along with optimization of the flow cytometric analysis protocol for the analysis of 50,000 cells. The performance of the assay was assessed for linearity and precision and correlated with the Kleihauer-Betke acid elution method.

RESULTS

The anti-HbF flow cytometric method showed good correlation with the Kleihauer-Betke method (r2 = 0.86) and superior precision with a CV < 15 percent for blood samples with > 0.1 percent fetal cells. Analysis of 150 blood samples from nonpregnant adults, including individuals with elevated HbF due to hemoglobinopathies and hereditary persistence of HbF, gave a mean value of 0.02 percent fetal cells, and all results were less than 0.1 percent.

CONCLUSIONS

The anti-HbF flow cytometric method for detection of fetal cells offers a simple, reliable, and more precise alternative to the Kleihauer-Betke manual technique for the assessment of fetomaternal hemorrhage. The method has additional potential applications for the study of HbF levels or frequency of adult red cells with low levels of HbF (F cells) in individuals with hemoglobinopathies.

Fetal nucleated erythrocytes (NRBCs) in chorionic villus sample supernatant fluids: an additional source of fetal material for karyotype confirmation

Fetal erythrocytes leak from the fetal capillaries at the time of chorionic villus removal. The purpose of this study was to determine if fetal nucleated erythrocytes (NRBCs) could be isolated from the chorionic villus sampling (CVS) supernatant fluid and used as an additional source of fetal material in order to confirm the fetal karyotype in cases of CVS mosaicism. One hundred CVS supernatant fluids were studied by simultaneous immunophenotyping, using a mouse antifetal haemoglobin antibody, UCH gamma, combined with fluorescent in situ hybridization (FISH) analysis using X- and Y-specific DNA probes. A chromosome 18 probe was also used in the case of a known male fetus with trisomy 18. Fetal haemoglobin (HbF)-positive cells were identified in 73 supernatant fluids and HbF-positive nucleated cells were present in 60 samples. The number of cells detected per sample showed great variation among the individual samples. FISH analysis was performed in 41 cases. FISH prediction of the fetal gender was concordant with the CVS karyotype in all cases, and the fetal trisomy 18 was correctly verified. In five cases in which Y sequences were detected, a small number of HbF-positive cells with two X signals were also identified; interestingly, in three of the five cases, the mother was a beta-thalassaemia carrier. This technique can be used as a quick and accurate method for the immediate verification of CVS results in cases of mosaicism, thus avoiding second-trimester amniocentesis.

Directing phage selections towards specific epitopes

It is possible to direct selections from antibody repertoires displayed on filamentous phage towards unique epitopes on protein antigens by competing with related molecules. A phage display repertoire of human single chain Fvs (scFvs) was panned three times against foetal haemoglobin (HbF). The selection was dominated by one clone with a Kd of 10 nM but yielded at least 17 others, all of which bound HbF but crossreacted with adult haemoglobin (HbA). To direct selection towards HbF-specific epitopes, the repertoire was preincubated with HbA in solution before each panning. Crossreactive scFvs can form complexes with the soluble HbA and thereby be prevented from binding the immobilized HbF. Four clones with preferential binding to HbF emerged under these conditions. One of these (Hb-1), with a Kd of 6 microM, had exquisite specificity for HbF and could distinguish cells expressing HbF from those expressing HbA by immunocytochemistry and flow cytometry. This antibody has an affinity that is 600-fold lower than the dominant crossreactive clone, and so only emerged under conditions of 'competitive deselection'. Thus, competitive deselection is a viable means for directing selections towards useful epitopes. It permits a more effective 'search' of phage display repertoires and allows the emergence of lower affinity clones with useful specificities. These clones may be useful in themselves or may serve as leads for in vitro affinity maturation.

Improved fetal nucleated erythrocyte sorting purity using intracellular antifetal hemoglobin and Hoechst 33342

Fetal nucleated erythrocytes (FNRBC) flow sorted from maternal peripheral blood, using monoclonal antibodies (mAb) that bind fetal cell surface antigens, are a noninvasive source of fetal DNA for prenatal diagnosis. These mAbs, however, also bind antigens shared by maternal cells. In sorted populations, this results in maternal cell contamination and low fetal cell purities, which complicates genetic analysis by fluorescence in situ hybridization (FISH) and polymerase chain reaction (PCR). Fetal hemoglobin, (alpha 2 gamma 2), has been proposed as a useful fetal marker. To improve fetal cell enrichment from maternal blood, we developed an intracellular staining protocol that combines anti-gamma mAb with Hoechst 33342 to identify and flow sort FNRBC. Artificial mixtures of male umbilical cord cells (as a source of fetal hemoglobin) and female adult, non-pregnant peripheral blood mononuclear cells were stained and flow sorted using this protocol. FISH analysis was performed using chromosome X and Y specific probes. Fetal cell purities were calculated by microscope confirmation of anti-gamma staining and counting the number of X and Y signals present after FISH. Results from microscope analyses showed a fetal cell yield of 39-100% and fetal cell purities of 59-73%. These purities are significantly higher than the .001-4.8% previously reported by us in maternal samples using cell surface staining protocols. FISH results demonstrated that 83-100% (mean = 98%) of anti-gamma positive cells were male, whereas 82-100% (mean = 92.5%) of anti-gamma negative cells were female. These results confirmed that the anti-gamma mAb is highly fetal specific. When applied to maternal blood samples, this protocol should lead to increased sensitivity for prenatal diagnosis.

Flow sorting of fetal erythroblasts using intracytoplasmic anti-fetal haemoglobin: preliminary observations on maternal samples

Monoclonal antibody to fetal haemoglobin (alpha 2 gamma 2) has been proposed as a fetal-specific reagent. We developed an intracellular staining protocol that combines fluorescein isothiocyanate or phycoerythrin conjugated anti-gamma with the DNA binding dye Hoechst 33342 to identify and flow sort fetal erythroblasts from maternal blood. Our preliminary observations on anti-gamma-positive cells sorted from four different pregnant women are described here, using fluorescence in situ hybridization (FISH) with chromosome-specific probes to identify fetal cells. Our data demonstrate that far fewer candidate fetal cells are sorted with this protocol than by current cell surface staining methods that employ the monoclonal antibody CD71. This results in increased fetal cell sorting purities. With this protocol, standard FISH techniques require modification due to the rigorous fixation with 4 per cent paraformaldehyde. Our initial data indicate the promise of this approach.

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.

Monoclonal antibody to the gamma chain of human fetal hemoglobin used to develop an enzyme immunoassay

A monoclonal antibody (mAb) that recognizes the gamma chain of human fetal hemoglobin (Hb F) has been produced by cell hybridization techniques. The mAb reacts with Hb F (alpha 2 gamma 2), Hb Bart's (gamma 4), and Hb Kenya (gamma-beta hybrid), but does not cross-react with Hb A (alpha 2 beta 2) or Hb A2 (alpha 2 delta 2). We describe a direct enzyme-linked immunoassay (ELISA) for measurement of Hb F, in which hemoglobins from standards or from unknown hemolysates are covalently bound to the wells of microtiter plates. The antigen is quantified by addition of the gamma-specific mAb, followed by anti-mouse IgG conjugated with horseradish peroxidase, and incubation with the substrate, tetramethylbenzidine. Absorbances at 630 nm are directly proportional to the amount of Hb F present in the standards or samples. Results for Hb F in 53 hemolysates agreed well with values obtained by "high-performance" liquid chromatography, RIA, alkali denaturation, and magnetic affinity immunoassay. This ELISA can detect a 0.5% proportion of Hb F in 1 h and offers distinct advantages over other techniques currently in use.

The use of monoclonal antibodies UCH beta and UCH gamma for the antenatal diagnosis of beta-thalassaemia

Monoclonal antibodies for the beta-globin chain of human HbA (UCH beta) and the gamma-globin chain of human HbF (UCH gamma) have been made. UCH beta indirectly labelled with rhodamine-labelled goat anti-mouse Ig and directly flouresceinated UCH gamma have been used, via double labelling immunofluorescence microscopy, to assay for the presence of beta-chains in fetal erythrocytes obtained at fetoscopy from fetuses at risk for beta-thalassaemia major. The results from 111 cases demonstrate that beta-chain synthesis of as low as 1.8% can be detected in fetal erythrocytes. The immunochemical labelling can be rendered more sensitive by the use of biotinylated UCH beta and avidin-FITC conjugates. This method is rapid and can be used for a sample that is highly contaminated with maternal erythrocytes.

A monoclonal antibody to hemoglobin F

A monoclonal antibody BMU7-17 which recognizes an antigenic site unique to the cyanogen bromide fragment, CB2 (residues 56 through 133) of the gamma-chain of human hemoglobin has been produced using cell hybridization techniques. The antibody does not crossreact with hemoglobin A, the isolated alpha- or beta-chains, or with hemoglobin of various mammals. Affinity chromatography on Staphylococcal protein A-Sepharose 4B and radial immuno-diffusion revealed the antibody to be of the mouse IgG 1 class. BMU7-17 identifies F cells in adult and in cord blood specimens, as demonstrated by an indirect immunofluorescence assay. The dissociation constant of the antibody as determined using tritiated hemoglobin F with a double antibody radioimmunoassay has a Kd = 1.2 X 10(-9) moles by Scatchard plot analysis.

Hybridoma monoclonal antibodies to human fetal haemoglobin

Monoclonal antibodies against human fetal haemoglobin (HbF) were obtained by fusion of mouse myeloma cells with spleen lymphocytes from mice immunized against HbF from human umbilical cord blood erythrocytes. Initial antibody screening was by indirect immunofluorescence assays on smeared cord blood and normal adult blood erythrocytes. The specificity of these antibodies was further studied by combined immunoprecipitation assays and direct or inhibition solid-phase enzyme immunoassays. The combined pattern enabled recognition of three types of antigenic determinants: (i) common to both HbF and HbA, by both immunofluorescence and enzyme immunoassays; (ii) common to both HbF and HbA by enzyme immunoassays, present on fixed cord blood erythrocytes and adult thalassaemic erythrocytes by immunofluorescence, but not found on fixed normal adult erythrocytes; and (iii) private HbF by both immunofluorescence and enzyme immunoassays.

Perturbations in the erythroid marrow progenitor cell pools may play a role in the augmentation of HbF by 5-azacytidine

In vivo observations on the kinetics of F cells and of fetal hemoglobin (HbF) synthesis and in vitro studies of erythroid progenitors, their number, and the gamma-gene expression in their progeny were carried out in baboons (Papio cynocephalus) treated with 5-azacytidine. Maximum effect on the increase of HbF production in vivo was observed only when an expanded erythroid marrow population was present. In these animals, as well as in normal animals, treatment resulted in a significant reduction of the late erythroid progenitor cell pools (erythroid clusters and erythroid colony-forming units, CFU-E) in the marrow. This reduction was more pronounced among those progenitors grown in the absence of added erythropoietin, and it was followed by a rebound a few days after treatment cessation, reflecting the accumulation of regenerating progenitors. An early increase in the in vitro synthesis of HbF in erythroid clusters and CFU-E colonies was observed. This increase was further documented at the cellular level, with immunofluorescent labeling of colonies with monoclonal anti-gamma-globin chain antibodies. In contrast to the findings in late progenitors, the number of erythroid burst-forming unit (BFU-E) colonies and the synthesis of HbF in these colonies was not influenced significantly by 5-azacytidine treatment. It is proposed that the toxic effects of 5-azacytidine on late progenitors, leading to faster mobilization of earlier progenitors to the next more mature compartment, play a role in the in vivo augmentation of HbF synthesis by this drug. This perturbation in the progenitor cell population kinetics and the presumed hypomethylation of the surviving differentiating cells may act synergistically to produce a maximum HbF response after 5-azacytidine treatment.

Quantitation of hemoglobins within individual red cells: asynchronous biosynthesis of fetal and adult hemoglobin during erythroid maturation in normal subjects

We outline a method for estimating either HbF or HbA content in single erythrocytes and their precursors. Our method depends on microphotometric assay of darkfield reflectance arising from individual pericellular immunoprecipitates developed with anti-HbF or anti-HbA. When uniform-diameter latex microspheres were used to normalize comparisons between preparations, mean coefficient of variation for HbF reflectance among separate preparations of the same sample was < 3%. Reflectance is a faithful (r = 0.99) linear function of the logarithm of picograms per cell in samples with known HbF or HbA content. The following features emerged from such analyses. First, despite the use of antigenically-specific antihemoglobins from different sources, the least detectable quantity of HbF (3.2 pg) and HbA (14.8 pg) remained invariant. Second, these detection thresholds depends on antihemoglobin affinity constants but are little influenced by antibody concentration. Third, our procedure is equally valid for persons with normal HbF constant (mean +/- SD = 4.4 +/- 0.3 pg per cell, 15 subjects) and for those with much higher levels. Fourth, like the percentage of HbF-bearing cells, HbF content is usually unchanging in serial samples. Fifth, the utility of the method is evidenced in bone marrow analyses of five hematologically normal persons in whom HbF content, unlike HbA content, remained constant throughout maturation from erythroblasts to erythrocytes. In vivo HbF biosynthesis is thus normally completed long before HbA production.

The isolation of the gamma subunit of fetal hemoglocin (HbF) and its use in a radioimmunoassay for HbF

A method is described for the purification, from fetal hemoglobin (HbF), of the fetal specific globin chain (gamma chain) in its native state. In the absence of alpha chain (the globin chain common to all adult human hemoglobins) gamma chain, when used as an immunogen, is able to express its unique antigenicity. Here, a specific, high titer antiserum raised against gamma chain has been used to establish a sensitive radioimmunoassay for HbF. This approach may be applicable to the measurement of other normal and abnormal hemoglobins.

F cells in gynaecologic malignancy

Red cells containing Hb F (F cells) were detected by immunofluorescence using a specific antiserum. In normal persons, the number of F cells was 2.5 +/- 1.1%. A significantly increased number of F cells was found in 65% of patients with cancer of the ovary, 69% of patients with cancer of the endometrium and in 22% of patients with cancer of the cervix. Highest values were obtained in cancer of the ovary and endometrium. There was no correlation between the number of F cells and stage of disease or degree of differentiation. It is postulated that in patients with malignant disease a humoral factor is produced which interferes with normal erythropoiesis resulting in a process of dedifferentiation.

Identification of hemoglobins within individual rhesus monkey (Macaca mulatta) erythrocytes

Rabbit and goat antibodies to monkey adult and fetal hemoglobin were prepared and purified to apparent monospecificity. After conjugation with fluorescein isothiocyanate, the antibodies were employed to identify the hemoglobin types within individual cells in peripheral erythrocyte smears. The percentage of neonatal monkey erythrocytes containing fetal hemoglobin was found to decrease with time. The existence of adult or fetal hemoglobin in the erythrocytes appeared to be mutually exclusive.

Evidence for significant hematopoiesis in the human thymus

Earlier studies on fetal thymus suggested that certain of the large pyroninophilic cells found there might have a hemopoietic role, and it was decided to determine the nature of these cells using histochemical and immunohistochemical methods. Thymic tissue from aborted fetuses, stillbirths, and neonatal deaths was examined histochemically using methods for the detection of chloroacetate esterase, peroxidase, and pseudoperoxidase, and by staining techniques for mast cells and eosinophils. Tissue was also examined using the indirect immunoperoxidase method for the presence of hemoglobin A (HbA) and F (HbF), for lysozyme (muramidase) and immunoglobins alpha, mu, gamma, kappa, lambda. Positive staining to some degree was seen in cells in the connective tissue stroma using all methods, and the cells stained corresponded to one or another of the types of pyroninophilic cells present. The finding of large cells with positive chloroacetate esterase and antilysozyme indicates the presence of granulopoiesis. Similarly, the presence of large nucleated cells with pseudoperoxidase and anti-hemoglobin (A and F) staining indicates the presence of erythropoiesis. Plasma cells were present in small numbers.

The Kenya form of hereditary persistence of fetal haemoglobin: structural studies and evidence for homogeneous distribution of haemoglobin F using fluorescent anti-haemoglobin F antibodies

Several members of a Ugandan family were heterozygous for the gamma beta fusion gene of Haemoglobin Kenya. Levels of Hb Kenya were significantly higher than those in subjects of previous reports, ranging from 20.68 to 23.35% of the total haemoglobin. The individuals had also 5-8% Hb F, consisting solely of alpha and Ggamma chains. Investigation of the distribution of Hb F among the red cells of Hb Kenya heterozygotes, using monospecific antibodies absorbed against pure Hb Kenya and rendered fluorescent by conjugation with fluorescein isothiocyanate, showed the presence of fetal haemoglobin in all red cells. The data suggest that the phenotype of the Hb Kenya trait resembles that of the Ggamma form of hereditary persistence of fetal haemoglobin rather than that of thalassaemia.