Isolation of fetal trophoblasts and nucleated erythrocytes from the peripheral blood of pregnant women for prenatal diagnosis of fetal aneuploides.

We present the results of a study of fetal cell isolation from the peripheral blood of 46 women in the first trimester of pregnancy. The trophoblasts were sorted with paramagnetic beads labelled with a novel monoclonal antibody 340 (Mab340) (Durrant et al., Prenat. Diagn., 14 (1994) 131). This was followed by triple density gradient enrichment to remove maternal lymphocytes and red blood cells. Nucleated red blood cells (NRBC) were sorted by incubation with ferromagnetic particles coated with Mab CD71, an antitransferrin receptor monoclonal antibody, and separation on a mini-MACS column. Sorted cells were sexed using nested PCR for the Y chromosome and the results compared with the karyotypic analysis of the CVS. The sensitivity in determining a male pregnancy with NRBC alone was 38% and with trophoblasts alone was 39%. Sorting for both cell types correctly predicted a male pregnancy in 10/18 or 56%. Of the 10 males correctly identified, 3 were diagnosed on NRBC alone, 3 on trophoblast alone and 4 with both cell types. As there are very few fetal cells in maternal blood, sorting for both will increase the yield and improve diagnosis. However the technique requires further development to improve sensitivity.