Detection of maternal DNA in human cord blood stored for allotransplantation by a highly sensitive chemiluminescent method

Human cord blood (CB), a rich source of hematopoietic stem and progenitor cells, is currently used for bone marrow reconstitution. However, the level of contamination of CB with maternal cells that could provoke graft-versus-host disease (GvHD) is a matter of concern. In the present study, 60 consecutive CB samples collected and stored in the Milan CB Bank, for which no maternal DNA was detected through genomic HLA typing, were examined to ascertain maternal cell contamination using polymerase chain reaction amplification of two minisatellites, apolipoprotein B gene (ApoB) and D1S80, followed by chemiluminescent detection. The sensitivity of the method employed in this study was 0.04%, comparable to that of radioactive methods. A maternal specific allele was found in 11 of the 60 CB units, at a level ranging from 1:100 to 1:2500. We could also detect the child paternal allele in 3 of the 30 mothers whose newborn was heterozygous at the loci examined. Our study indicates that maternal cells are present in 18.3% of the 60 samples examined. The clinical relevance of such a presence remains to be established. In our opinion, information on maternal cell contamination should be included within the quality control tests performed before delivering a unit.