Are fetal cells in maternal plasma really there? We think they are

We describe a single centrifugation procedure that resulted in the recovery of fetal cells in maternal blood in 77% of normal male pregnancies and in 87.5% of aneuploid pregnancies. There was an average yield of one fetal cell/1,993 maternal cells in normal pregnancies, which increased to one in 994, in aneuploid pregnancies.

Proof of homologous blood transfusion through quantification of blood group antigens

BACKGROUND AND OBJECTIVES

Athletes may illegally enhance endurance performance by transfusing homologous red blood cells (RBCs) and thereby increasing the oxygen carrying capacity of their blood. Detecting this dangerous practice is difficult by currently used methods. The aim of this work was to develop tests capable of detecting a mixed red cell population by flow cytometry, utilizing the likelihood of differences in minor blood group antigens.

DESIGN AND METHODS

Twelve antisera directed against blood group antigens, derived from donor plasma, were used in conjunction with a secondary antibody directly conjugated with fluorescein to label IgG-coated RBCs. Optimal concentrations of RBCs and antibodies were determined on panel cells used in blood banking for the identification of specific antibodies. Blood samples from 25 patients purportedly transfused with 1-3 units of RBCs were screened for evidence of transfusion, and the percentages of antigen-positive and antigen-negative red cells were automatically calculated by the software installed in the flow cytometer after setting gates around these populations on histograms of fluorescence.

RESULTS

Mixed RBC populations were identified in 22 of 25 patients tested. The three patients with antigenically homogeneous populations of RBCs were subsequently found not to have received their scheduled transfusions.

INTERPRETATION AND CONCLUSIONS

This technique can detect small (<5%) populations of cells that are antigenically distinct from an individual's own RBCs. These results show the potential for flow cytometry to identify illicit homologous blood transfusion in athletes, and suggest the risk of false positives may be low.

A case of maternal reaction due to fetomaternal transfusion

We present here a case of maternal reaction to fetomaternal transfusion complicated by subchorionic hemorrhage. A 40-year-old woman, gravida 2, para 0, was admitted to our hospital at 25 weeks' gestation because of high blood pressure. On the morning of 32 weeks and 2 days' gestation, she developed sudden onset nausea, dyspnea and regular uterine contractions. Blood pressure was 80/50 mmHg and pulse was 110 beats/minute. At this time, her WBC, hemoglobin and platelets were decreased significantly. Two hours after onset, the patient's condition improved spontaneously. Increased serum alpha-fetoprotein level (3.0 multiple of median) was observed. She was suggested to be a case of acute fetomaternal transfusion.

Identification of fetal mesenchymal stem cells in maternal blood: implications for non-invasive prenatal diagnosis

Strategies for genetic prenatal diagnosis on fetal cells in the maternal circulation have been limited by lack of a cell type present only in fetal blood. However, the recent identification of mesenchymal stem cells (MSC) in first trimester fetal blood offers the prospect of targeting MSC for non-invasive prenatal diagnosis. We developed protocols for fetal MSC enrichment from maternal blood and determined sensitivity and specificity in mixing experiments of male fetal MSC added to female blood, in dilutions from 1 in 10(5) to 10(8). We then used the optimal protocol to isolate fetal MSC from maternal blood in the first trimester, using blood taken after surgical termination of pregnancy as a model of increased feto-maternal haemorrhage. In model mixtures, we could amplify one male fetal MSC in 2.5 x 10(7) adult female nucleated cells, yielding a 100% pure population of fetal cells, but not one fetal MSC in 10(8) nucleated cells. Fetal MSC were identified in one of 20 post-termination maternal blood samples and confirmed as fetal MSC by XY fluorescence in-situ hybridization (FISH), immunophenotyping and osteogenic and adipogenic differentiation. We report the isolation of fetal MSC from maternal blood; however, their rarity in post-termination blood suggests they are unlikely to have a role in non-invasive prenatal diagnosis. Failure to locate these cells routinely may be attributed to their low frequency in maternal blood, to sensitivity limitations of enrichment technology, and/or to their engraftment in maternal tissues soon after transplacental passage. We speculate that gender microchimerism in post-reproductive maternal tissues might result from feto-maternal trafficking of MSC in early pregnancy.

Cellular microchimerism as a lifelong physiologic status in parous women: an immunologic basis for its amplification in patients with systemic sclerosis

OBJECTIVE

To quantitatively measure male DNA in blood from women with systemic sclerosis (SSc) and from controls and to evaluate in vitro the modulation of the microchimeric cell population size following immunologic stimuli that were expected to trigger antigen-specific T cells.

METHODS

A real-time polymerase chain reaction for a Y chromosome sequence was used to measure male DNA in blood from women with SSc and from controls who gave birth to sons. The in vitro change in the microchimeric cell population size was measured following immunologic stimuli, which were expected to trigger antigen-specific T cells.

RESULTS

Cellular microchimerism was found in SSc patients and controls, but the absolute amount of male DNA was higher in the patients, and the in vitro addition to blood mononuclear cells of an anti-CD28 costimulatory signal acted as a powerful amplification of microchimeric cells in 3 patients with SSc but not in controls.

CONCLUSION

Cellular microchimerism is a physiologic phenomenon in parous women. In SSc patients, cellular microchimerism is accounted for by a higher number of cells that have the characteristics of T lymphocytes specific to maternal allogeneic antigens.

Detection of gamma-globin mRNA in fetal nucleated red blood cells by PNA fluorescence in situ hybridization

OBJECTIVES

Fetal nucleated red blood cells (NRBC) that enter the peripheral blood of the mother are suitable for non-invasive prenatal diagnosis. The application of peptide nucleic acid (PNA) probes for tyramide amplified flow fluorescence in situ hybridization (FISH) detection of gamma-globin mRNA in fixed fetal NRBC is investigated.

METHODS

Hemin-induced K562 cells or nucleated blood cells (NBC) from male cord blood were mixed with NBC from non-pregnant women and analysed using both slide and flow FISH protocols. Post-chorionic villus sampling (CVS) blood samples from pregnant females carrying male fetuses were flow-sorted (2 x 10(6) NBC/sample). Y chromosome-specific PNA FISH was used to confirm that the identified gamma-globin mRNA stained cells were of fetal origin.

RESULTS

Flow FISH isolated gamma-globin mRNA positive NBCs showing characteristic cytoplasmic staining were all Y positive. The amplification system generated a population of false positive cells that were, however, easy to distinguish from the NRBCs in the microscope.

CONCLUSION

The gamma-globin mRNA specific PNA probes can be used for detection and isolation of fetal NRBCs from maternal blood. The method has additional potential for the study of gamma-globin mRNA levels or the frequency of adult NRBC (F cells) in patients with hemoglobinopathies.

Limited expression of Fas and Fas ligand in fetal nucleated erythrocytes isolated from first trimester maternal blood

OBJECTIVE

Intact fetal cells isolated from maternal blood can be used for non-invasive gender determination and genetic diagnosis. Recent studies demonstrating a large amount of cell-free fetal DNA in maternal plasma suggest that the circulating fetal DNA may result from fetal cells undergoing apoptosis. In the present study we evaluated the potential role of Fas and Fas ligand (FasL) cell surface expression with respect to apoptosis induction in fetal cells isolated from maternal blood.

METHODS

We flow sorted candidate fetal cells that were gamma chain-positive and Fas- or FasL-positive or -negative, and subsequently analysed them by fluorescence in situ hybridization (FISH) analysis using X and Y chromosome-specific probes.

RESULTS

Among all gamma hemoglobin-positive cells, there was a significant difference in the percent of cells expressing Fas versus FasL (4.4 and 12.3, respectively). We found no significant correlation between the total number of fetal nucleated red blood cells (NRBCs) and gestational age or the presence of Fas- and FasL-positive cells. From approximately 7 ml of maternal peripheral blood, most of the confirmed fetal (XY) cells were found in the Fas- and FasL-negative sorted population; the average numbers were 12.8 and 15.7, respectively.

CONCLUSION

We conclude that fetal NRBCs express FasL more than Fas, although most fetal NRBCs in first trimester maternal blood samples do not express Fas or FasL. This suggests the absence of a functional Fas/FasL apoptotic system in fetal NRBCs, and that programmed cell death in these cells, which may lead to circulating fetal DNA in maternal plasma, probably occurs by another pathway.

Prediction of fetal Rh D and Rh CcEe phenotype from maternal plasma with real-time polymerase chain reaction

Real-time PCR methods for the detection of RHD and the C, c, and E allele of RHCE were applied for the prediction of fetal Rh phenotype using maternal plasma. In one of 36 samples investigated the DNA extraction failed. When we tested the remaining 35 samples for Rh antigens which were absent on the mother's red cells, the fetal D-status was correctly determined in 26 of 27 cases (1 false negative). Fetal C was tested correctly in 23 samples, c was true positive in the only c-negative woman and the fetal E-status was correctly determined in 35 cases. In conclusion real-time PCR of maternal plasma is a non-invasive method to determine fetal RH genotype. However, more studies are required for routine applications because the method is not 100% sensitive.

Incidental diagnosis and tempestive therapy in a case of neonatal alloimmune thrombocytopenia due to anti-HPA-5b

Neonatal alloimmune thrombocytopenia (NAIT) is usually attributable to HPA-1a antibodies. The authors report a case of incidentally diagnosed thrombocytopenia in a small for gestational age infant. A NAIT was suspected and she was successfully treated with intravenous IgG. The direct and indirect platelet suspension immunofluorescence test (PSIFT) in maternal blood suggested alloimmunization to HPA-5b. Empiric treatment with IgG could be useful in case of clear suspect even in absence of confirmed diagnosis.

Possible contribution of microchimerism to the pathogenesis of Sjögren's syndrome

OBJECTIVES

Microchimerism of foetal cells occurs during most pregnancies. Two autoimmune diseases, systemic sclerosis (SSc) and Sjögren's syndrome (SS), have many clinical and pathological similarities to chronic graft-vs-host disease (GVHD). These findings suggest that anti-maternal graft-vs-host reaction by foetal cells may be involved in the pathogenesis of the diseases. To explore this hypothesis, we examined foetal DNA in peripheral blood of 59 women and in salivary glands from 28 women.

METHODS

DNA extracted from peripheral blood and the affected minor salivary glands was analysed for the Y-chromosome-specific gene using a nested polymerase chain reaction (PCR) test. In the minor salivary gland specimens, the Y-chromosome-positive foetal cells were identified by in situ hybridization with a Y-chromosome-specific DNA probe.

RESULTS

In peripheral blood, there was no significant difference between controls and patients with SSc or SS. In salivary glands, foetal DNA was detected in 11 of 20 women with SS but in only one of eight normal controls using PCR test. Additionally, foetal cells were clearly detected in three out of eight women with SS by the use of in situ hybridization.

CONCLUSIONS

The identification of foetal cells in salivary glands suggests that anti-maternal GVHD may be involved in the development of SS.

Comparison of methods for erythroblast selection: application to selecting fetal erythroblasts from maternal blood

BACKGROUND

Many methods have been employed to obtain fetal cells from maternal blood for prenatal diagnostics, but there has been little work done that compares the efficacy of different methods. This study presents a comparison of two commonly used methods for selecting erythroblasts with selection directly from whole blood.

METHODS

Erythroblasts were isolated from maternal blood by either differential lysis or density separation, followed by selection with an antibody to the transferrin receptor. These methods were compared with antibody selection directly from whole blood. The total yield of erythroblasts was determined for each method.

RESULTS

Red cell lysis is not recommended because the lysis step cannot be well controlled. Density separation followed by antibody selection works well. However, a faster and simpler method, antibody selection directly from whole blood using Immunicon Ferrofluid and magnetic separators, works as well and has the potential to yield even more cells.

CONCLUSIONS

Considering the need for a simple and quick method for selecting fetal cells from maternal blood, we suggest selection directly from whole blood.

A novel method for depositing erythroid cells onto glass slides for fetal cell analysis

BACKGROUND

We have developed a method for selecting erythroblasts from blood, the first step toward identifying fetal cells in maternal blood for diagnostic purposes. Because the selection method results in a large number of positive cells, we needed to develop new methods to deposit the cells onto slides and to modify in situ hybridization procedures to enable detection of fetal cells.

METHODS

We utilized Nunc flaskettes to increase the slide surface area available for cell deposition. The ability of erythroid lineage cells to adhere to several surface modifications was examined. In situ hybridization methods were tested to find the best approach that is compatible with these cell preparations.

RESULTS

The best glass slide coating for erythroid cells was found to be an antibody to glycophorin A, a red cell surface antigen. We were able to get excellent in situ hybridization signals in cells on flaskettes by modifying fixation and pretreatment parameters.

CONCLUSIONS

The methods described here appear to be the best way of attaching a large number of erythroid lineage cells to slides and of detecting them by in situ hybridization.

Microchimerism in a female patient with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a serious multisystem disease that has a striking propensity to affect women. The cause of SLE remains elusive. Fetomaternal cell trafficking, or the passage of fetal cells into the maternal circulation, is now a well-established phenomenon. In addition, fetal cells have been implicated in the development of preeclampsia and in the pathogenesis of scleroderma. We undertook this study to determine whether fetomaternal cell trafficking might also be involved in pathogenic processes in SLE. Fluorescence in situ hybridization analysis was performed using X and Y chromosome-specific probes on affected and unaffected tissue obtained at autopsy from a woman who had previously given birth to 2 males and who had died of complications of SLE. The goal of the analysis was to detect the presence of male cells of putative fetal origin. Male cells were found in every histologically abnormal tissue type that was examined, but were not found in histologically normal tissue. These data suggest that fetal cells may be associated with SLE. It is unclear whether their presence may be related to disease causation, an effect of disease progression, or unrelated to disease pathology. However, this case study is an important step toward understanding the potential relationship between fetomaternal cell trafficking and SLE pathology.

[Differential diagnosis of thrombocytopenia in pregnancy]

Thrombocytopenia (< 150,000/microliter) is a common finding, occurring in 7-8% of pregnancies. Some conditions, such as gestational thrombocytopenia pose no maternal or fetal risks. Idiopathic thrombocytopenic purpura (ITP) is an acquired haematologic disorder, common among children and adults, with unknown etiology and autoimmune pathogenesis. The incidence of severe fetal and neonatal thrombocytopenia is very rare, and neonatal intracranial hemorrhage is unlikely to be related to the mode of delivery. Alloimmune thrombocytopenia occurs with an incidence of 1/1,000 livebirths and is induced by a maternal alloimmunization against fetal platelet antigens. The incidence of intracranial haemorrhage in the fetus and neonate is the highest for any immune thrombocytopenia. The HELLP syndrome is a severe, unpredictable and life-threatening complication of preeclampsia, characterized by a triad of hemolysis, elevated liver enzymes and low platelet counts. HELLP syndrome develops in the third trimester but can occur postpartum. Hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP) are syndromes of microangiopathic hemolytic anemia, and thrombocytopenia. During pregnancy, TTP usually presents in the second trimester, whereas HUS develops in the postpartum period. Heparin-induced thrombocytopenia type II is a serious, immune-mediated complication of heparin therapy.

Fetal cells in the mother: from genetic diagnosis to diseases associated with fetal cell microchimerism

Fetal cells circulate in the blood of pregnant women. When the gestation is normal, fetal cells are low in number. Complications of pregnancy, such as pre-eclampsia, or fetal cytogenetic abnormalities, such as Down's syndrome, increase fetomaternal transfusion. The isolation of fetal cells from maternal blood is currently under active investigation as a non-invasive method for prenatal diagnosis. The fetal cells that are most commonly used for non-invasive genetic diagnosis, the nucleated erythrocyte and the trophoblast, are highly differentiated and do not persist post-partum. In the context of studying fetal cells in maternal blood it was discovered that fetal progenitor cells originating from a prior pregnancy could also be detected. This led to the appreciation that unlike fetal DNA in plasma, which is cleared almost immediately following delivery, fetal cells persist for decades post-partum. Following pregnancy, labor, and delivery, a woman becomes a chimera. Transfused fetal stem and progenitor cells appear to be capable of further differentiation and migration to maternal organs. A further research agenda is needed to explore the newly appreciated phenomenon of bi-directional fetomaternal cell trafficking. Any consideration of the fetus as a patient must also consider the fetus as a potential source of therapeutic stem cells for the mother.

Fetal cells from maternal blood: purpose, biological questions, technical challenges

The maternal peripheral blood circulation can serve as a source of fetal cells for the prenatal diagnosis of genetic abnormalities, eliminating the need for fetal cell sampling by invasive techniques. However, the extreme scarcity of these cells leads to a variety of biological questions and technical hurdles on the way to a clinical test. On the biological side, we need to know the numbers of fetal cells, their distinguishing properties, and the variables that affect these properties. On the technical side, we need to identify fetal cells and maximize both yield and purity of the isolation procedure. Here we review the questions and challenges as they present themselves in our specific approach to the fetal cell isolation project. We also briefly discuss the question of whether these cells could help to diagnose fetal infections.

[Problem-solving in immunohematology: interpretation of ABO typing and its difficulties]

Practice in immunohematology is replete with complex problems that require practitioners' problem-solving performance. In immunohematology, the acquisition of the reasoning process and necessary skills for making clinical decisions is based on teaching problem-solving strategies which potentially reduce errors and improve patient outcome. We discuss the recognition and resolution of the common causes of discrepancies in ABO typing results using problem-solving strategies.

Detection of male and female fetal DNA in maternal plasma by multiplex fluorescent polymerase chain reaction amplification of short tandem repeats

The purpose of this study was to develop a fluorescent polymerase chain reaction (PCR) assay for the detection of circulating fetal DNA in maternal plasma. Maternal DNA extracted from plasma samples of pregnant women at term and newborn DNA isolated from cord blood were used to genotype 12 mother/child pairs at nine different polymorphic short tandem repeat loci. Multiplex fluorescent PCR was used to detect fetus-specific alleles in the corresponding maternal plasma samples. Fetus-specific alleles were found in all maternal plasma samples studied. Using these polymorphic repeat sequences, every mother/child pair was informative in at least four of nine loci. Paternally inherited fetal alleles were detected in 84% of informative short tandem repeats. This approach may have implications for non-invasive prenatal diagnosis. Compared with other fetal DNA detection systems that use fetus-derived Y sequences to detect only male fetal DNA in maternal plasma, our proposed technique can be applied to both female and male fetuses.

Investigation of maternal blood enriched for fetal cells: role in screening and diagnosis of fetal trisomies

Prenatal diagnosis of chromosomal abnormalities relies on assessment of risk followed by invasive testing in the group with highest risk. Assessment of risk by a combination of maternal age and fetal nuchal translucency and invasive testing in the 5% of the population with the highest risk would identify about 80% of trisomy 21 pregnancies. Preliminary reports suggest that chromosomal abnormalities can also be diagnosed by fluorescent in situ hybridization (FISH) in maternal blood enriched for fetal cells. This study examines the potential role of this method on the prenatal diagnosis of fetal trisomies. Maternal blood was obtained before invasive testing in 230 pregnancies at 10-14 weeks of gestation. After enrichment for fetal cells, by triple density centrifugation and anti-CD71 magnetic cell sorting, FISH was performed and the proportion of cells with positive signals in the chromosomally normal and abnormal groups was determined. Fetal karyotype was normal in 150 cases and abnormal in 80 cases, including 36 with trisomy 21. Using a 21 chromosome-specific probe, three-signal nuclei were present in at least 5% of the enriched cells from 61% of the trisomy 21 pregnancies and in none of the normal pregnancies. For a cut-off of 3% of three-signal nuclei the sensitivity for trisomy 21 was 97% for a false positive rate of 13%. Similar values were obtained in trisomies 18 and 13 using the appropriate chromosome-specific probe. Examination of fetal cells from maternal blood may provide a noninvasive prenatal diagnostic test for trisomy 21 with the potential of identifying about 60% of affected pregnancies. Alternatively, this technique can be combined with maternal age and fetal nuchal translucency as a method of selecting the high-risk group for invasive testing. Potentially, 80% of trisomy 21 pregnancies could be identified after invasive testing in less than 1% of the pregnant population.