Heterogeneity of F cells in ß-thalassemia.

BACKGROUND: Fetal hemoglobin (HbF), which is largely replaced after birth by the adult Hb, is concentrated in a few "F cells." Their number significantly increases in certain physiologic and clinical situations, including in ß-thalassemia (ß-thal). Their quantification is used to detect fetal-maternal hemorrhage (FMH), where fetal cells enter the maternal circulation. We were confronted with a pregnant woman with ß-thal who was suspected to have FMH. To establish the usefulness of a flow cytometric procedure to differentiate between fetal cells and the maternal F cells, we screened adult ß-thal patients. STUDY DESIGN AND METHODS: Blood samples were simultaneously stained with fluorescent antibodies to HbF and to carbonic anhydrase (CA) isotype II, which is specific to adult red blood cells (RBCs). RESULTS: A heterogeneous distribution of RBCs with respect to HbF and CA expression was observed: adult non-F cells (CA+HbF-) and F cells (CA+HbF+/HbF++) as well as F cells with characteristics of fetal cells (CA-HbF++). CONCLUSIONS: The presence of CA-HbF++ RBCs in nonpregnant women, and even men, with thal indicates that the CA/HbF method is inappropriate for detection of FMH. The coexistence of F cells carrying fetal or adult markers suggests that they originate from two types of stem cell, adult and fetal, lineages. Normally, the fetal lineage is insignificant, but in ß-thal, as HbF-containing RBCs have a selective advantage, the "fetal" lineage gains significance.

Role of the vascular endothelial growth factor in the inverse relationship between increased nuchal translucency thickness and fetomaternal transfusion.

OBJECTIVE: To elucidate the possible etiological role of the vascular endothelial growth factor (VEGF) in the inverse correlation between nuchal translucency (NT) thickness and fetomaternal transfusion (FMT). METHODS: The level of FMT was determined prospectively in 80 viable, singleton pregnancies in which 10-14-week ultrasonographic scanning, NT thickness measurement; chorionic villus sampling (CVS) for fetal karyotyping and VEGF concentration determination were performed. The grouping procedures were based either on NT thickness (<2 MoM in Group I, and ≥2 MoM in Group II), or on karyotype (euploid in Group A, and aneuploid in Group B). The level of FMT was determined via maternal serum α-fetoprotein levels before and after CVS. The FMT and the VEGF concentration of the chorionic tissue were analysed in comparisons between Groups I and II, and between Groups "A" and "B". RESULTS: The mean level of FMT after CVS was 72.5±21.3 µL and 19.28±5.4 µL in Groups I (n=44) and II (n=36), respectively (P<0.02). The VEGF concentration of the chorionic tissue in Groups I and II was 40.6±16.7 pg/mg protein and 21.1±6.3 pg/mg protein, respectively (P=0.28). The mean level of FMT was 57.9±15.0 µL and 8.1±3.9 µL in Groups A and B, respectively (P<0.003). The VEGF concentration of the chorionic tissue in Groups A and B was 25.9±10.7 pg/mg protein and 21.3±11.3 pg/mg protein, respectively (P=0.77). CONCLUSION: No difference exists in the VEGF concentration in the aspirated chorionic tissue between Groups I and II and between Groups A and B. A higher level of FMT was observed among the aneuploid pregnancies after CVS than among the euploid cases. Chorionic VEGF does not influence the inverse relationship between the pre-CVS NT thickness and FMT.

Rapid clearance of fetal cells from maternal circulation after delivery.

We previously reported increased apoptosis in the maternal circulation during pregnancy, partly accounting for the presence of cell-free fetal DNA in maternal plasma. In the current study, apoptosis was quantitated in 60 peripheral blood samples obtained from 15 women sequentially tested postpartum using the binding of annexin V. FISH with X/Y probes was performed on annexin V-positive cells isolated by MACS in patients with male fetuses to estimate the proportion of fetal cells among the apoptotic cell population. Twenty-four women at the thirty-seventh to thirty-eighth week of gestation and 35 nonpregnant females were used as controls. Apoptosis rate in the thirty-seventh to thirty-eighth week was 12.5% (9.2-14.7%). At 30 minutes, 12 hours, 24 hours, and 48 hours postpartum, it was 25.1% (16.8-28.5%), 12.5% (10.9-14.1%), 6.1% (4.8-7.1%), and 2.3% (1.3-3.0%), respectively. Male apoptotic cells were identified in all cases with male fetuses at 37 to 38 weeks of gestation, and the mean proportion was 9.9% (5.9-13.2%). The proportion of fetal cells 30 minutes after delivery was 14.8% (12.5-25.5%) and 12 hours postpartum 2.1% (0.8-4.1%). Male fetal apoptotic cells were detected in three of eight samples collected 24 hours after delivery from women who delivered males, at frequencies of 0.10%, 0.15%, and 0.25% (mean 0.16%). There were no fetal apoptotic cells 48 hours after delivery. Apoptosis partly accounts for the clearance of fetal cells from the maternal circulation. Because it is a rapid reaction, completed within 2-3 hours, persistence of fetal cells is possibly due to apoptosis-resistant progenitors or to defective regulation of apoptosis, leading to fetal cell microchimerism associated with autoimmune diseases.

Changes in circulating alphafetoprotein following administration of mifepristone in first trimester pregnancy.

The occurrence of fetomaternal haemorrhage was investigated in 30 women by measuring maternal serum alphafetoprotein (AFP) levels before and after the administration of mifepristone (RU 486) for termination of first trimester pregnancy. A significant rise in AFP levels was seen in 21 women (70%), the increase ranging from 6 to 660% of baseline levels. The apparent frequency of fetomaternal haemorrhage was similar to that reported previously for surgical termination of first trimester pregnancies.

PIP: Fetomaternal hemorrhage-induced rises in circulating alphafetoprotein (AFP) levels can occur as a result of invasive procedures in the 1st half of pregnancy, including amniocentesis and induced abortion. In this study, 30 women under 9 weeks of gestation were given a single oral dose of 600 mg of RU-486 followed 48 hours later be insertion of a vaginal pessary containing 1 mg of gemeprost. All 30 women aborted within 2-4 hours of gemeprost administration. There was moderate bleeding for 24 hours after the abortion in 2 women. In the 4-hour period following RU-486 administration, subjects did not show any change over baseline values in AFP levels. However, 2 days later, before gemeprost administration, 21 women showed a significant increase (median of 87%, range 6-660%) in AFP. This finding suggests that fetal blood can enter the maternal circulation during pregnancy termination, and the RU-486 is not able to counteract this process. The 70% rate of elevation of AFP with RU-486 is in fact higher than that recorded for surgical termination of 1st-trimester abortion (58%). Surprising was the finding that these changes in circulating AFP occurred before the administration of prostaglandin.