Characterization of mononuclear cell subpopulations in normal fetal peripheral blood.

It is now possible to characterize fetal peripheral blood mononuclear cells (FPBMC) from normal fetuses sampled in utero under ultrasound guidance. The surface phenotype of FPBMC from 25 fetuses, between the 20th and the 26th week of gestation, was studied using standard reagents that are known to delineate mononuclear cell subsets in adult peripheral blood. Results were compared with those obtained in neonates (cord blood) and adults. The major subsets of adult PBMC are represented in fetal blood with few qualitative differences: 20% of FPBMC are not recognized, the percentage of T cells is lower with a higher ratio T4/T8, the fraction of cells that express DR molecule is very high, and the distribution of NK antigens is different in fetuses. B cells and monocytes are in equal proportion. This work represents a prerequisite for future functional studies, and provides normal fetal values that will be useful for prenatal diagnosis of congenital immunodeficiency.