Improved specificity of NRBC detection in chorionic villus sample supernatant fluids using anti-zeta and anti-epsilon monoclonal antibodies.
OBJECTIVE
Fetal erythrocytes leak from fetal capillaries at the time of chorionic villus sampling (CVS). It has been reported that in approximately 60% of CVS cases fetal nucleated red blood cells (NRBC) can be isolated from the supernatant fluid by immunophenotyping with monoclonal antibody (Ab) against the gamma-chain of fetal hemoglobin and used as an additional source for confirmation of the fetal karyotype. However, the increased prevalence of beta-thalassemia mutations in countries such as Greece results in many pregnant women who produce gamma-positive cells. This makes it difficult to distinguish between the fetal and maternal origin of the NRBC. Use of Abs against embryonic hemoglobin chains zeta and epsilon may increase specificity for fetal NRBC detection.


METHODS
Mouse monoclonal Abs against Hb-zeta and Hb-epsilon were used in order to examine if specificity for fetal NRBC detection in CVS supernatant fluids could be improved. 41 samples were studied using anti-zeta and 20 using anti-epsilon monoclonal Abs.


RESULTS
Anti-zeta or anti-epsilon positive erythrocytes were, respectively, identified in 52 of 61 CVS samples and anti-zeta or anti-epsilon positive NRBC were present in all cases. The mean number of Hb-positive erythrocytes identified with the anti-zeta Ab was 58 and the mean number of NRBC 29. The mean number of anti-epsilon positive erythrocytes was 30 and of NRBC 23. FISH with X and Y chromosome specific probes was performed in 26 cases and the results were concordant with the CVS karyotype. Statistical analysis using the correlation test showed that anti-zeta and anti-epsilon were more specific for the detection of embryonic NRBCs.


CONCLUSIONS
Since embryonic monoclonal Abs show increased specificity, they should be preferentially used for NRBC detection in CVS supernatant fluids. Furthermore, the increased specificity of anti-zeta and anti-epsilon Abs may considerably improve prenatal diagnosis from fetal cells isolated from maternal circulation.
Mavrou
A
A
Genetic Unit, 1st Department of Pediatrics, Athens University Medical School, Athens, Greece. ariamav@hol.gr
Kolialexi
A
A
Zheng
Y L
YL
Metaxotou
C
C
Bianchi
D W
DW
D000818:Animals; D000911:Antibodies, Monoclonal; D000918:Antibody Specificity; D015193:Chorionic Villi Sampling; D004900:Erythroblasts / Q000473:pathology*; D005260:Female; D005312:Fetal Blood; D005914:Globins / Q000276:immunology*; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D051379:Mice; D011247:Pregnancy
D000911:Antibodies, Monoclonal; D005914:Globins