Identification of Fetal Nucleated Red Blood Cells in the Maternal Circulation during Pregnancy Using Anti-Hemoglobin-ε Antibody

Abstract

Aim: To investigate the use of anti-hemoglobin-Ε 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-Ε. FISH with X, Y and 21 chromosome-specific probes was performed in 29 cases. Results: The mean number of Ε-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 Ε-positive nucleated red blood cells (NRBCs) isolated from carriers and noncarriers of β-thalassemia. FISH analysis was successful in 24 cases. In 4 cases with known male fetuses, an average of 4.7 Ε-positive cells showed a Y signal. In 4 cases with Down syndrome, all Ε-positive cells showed 3 signals for chromosome 21. Conclusion: Anti-hemoglobin-Ε 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.