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 per ipheral blood of 46 women in the first trimester of pregnancy. The tro phoblasts were sorted with paramagnetic beads labelled with a novel mo noclonal antibody 340 (Mab340) (Durrant et al., Prenat. Diagn., 14 (19 94) 131). This was followed by triple density gradient enrichment to r emove maternal lymphocytes and red blood cells. Nucleated red blood ce lls (NRBC) were sorted by incubation with ferromagnetic particles coat ed with Mab CD71, an antitransferrin receptor monoclonal antibody, and separation on a mini-MACS column. Sorted cells were sexed using neste d PCR for the Y chromosome and the results compared with the karyotypi c 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 5 6%. Of the 10 males correctly identified, 3 were diagnosed on NRBC alo ne, 3 on trophoblast alone and 4 with both cell types. As there are ve ry few fetal cells in maternal blood, sorting for both will increase t he yield and improve diagnosis. However the technique requires further development to improve sensitivity.