Applicability of Four New Antibodies for the Detection of Fetal Nucleated Cells Out of Maternal Blood by FISH Analysis

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Abstract
The availability of fetal cells from the maternal peripheral blood opens up the possibility for a noninvasive prenatal diagnosis. Until now this prospect has been hampered by the fact that there are no highly specific antibodies to fetal cells. In the present study, four as yet untested monoclonal antibodies – 2G5, 3F9, EPO-R and Flk1 – were analyzed in view of their effectiveness to stain fetal nucleated cells. Therefore, 20 ml of peripheral blood from 40 women carrying a male fetus were collected in the 16th to 28th weeks of pregnancy. Mononucleated cells, enriched by density gradient, were stained with one of the four antibodies and isolated with magnetic cell sorting. Subsequently, fluorescence in situ hybridization with chromosome X and Y centromere probes was performed which allowed us to analyze the maternal or fetal origin of the enriched cells. For evaluation, 500 nuclei per case were examined. The antibody 3F9 detected 0.2 cells on average (n = 5), 2G5 1.2 (n = 11), EPO-R 1.6 (n = 10) and Flk1 1.8 cells (n = 8) with fetal specific Y-positive hybridization signals. The antibody against CD71 (n = 6) used as control gave no Y-specific signals. Considering these results, the tested antibodies, especially Flk1, appear to be more successful in detecting fetal cells than the commonly used CD71 antibody.