PRACTICAL AND THEORETICAL IMPLICATIONS OF FETAL/MATERNAL LYMPHOCYTE TRANSFER

Abstract

Lymphocyte cultures were prepared from peripheral-blood samples taken from thirty pregnant women. In twenty-one cultures one or more euploid metaphase figures with 5 small acrocentric chromosomes interpreted as 46/" XY " were found. Nineteen of the twenty-one women gave birth to male infants, and two gave birth to females (P=0·0001). The two "false-positive" results were in women in whom only 1 cell with 5 small acrocentric chromosomes had been found, whereas all ten patients in whom 2 or more cells were found gave birth to males. Artefact or chimærism for fetal 46/XY cells persisting from an earlier pregnancy may account for the two false-positive results. In nine other women, no " XY " cells were found. Six gave birth to female infants while three gave birth to males. Cells with 46/XY karyotype in the maternal circulation were detected as early as the 14th week of gestation (the earliest age studied). The data suggest that the fetomaternal transfer of lymphocytes is common, happens at least as early as the 14th week of gestation, and may be a consequence of transplacental migration of circulating fetal lymphoid cells, as well as leakage of blood. The antenatal diagnosis of a male fetus can be made by karyotypic analysis of lymphocytes in maternal blood. Similarly, it should be possible to identify fetal chromosome abnormalities by this procedure. Transfer of fetal lymphocytes to the mother may play a part in the acceptance of the fetus as a homograft.