PHENOTYPIC CHARACTERISTICS OF LYMPHOCYTE POPULATIONS ISOLATED FROM MIDDLE GESTATION HUMAN PLACENTA

In order to characterize the phenotypic composition of populations of lymphoid cells in maternal and fetal tissues during the period of midd le gestation, mononuclear cells were isolated from maternal peripheral blood, fetal spleen, fetal thymus and placenta of 18-24 week pregnanc ies. Peripheral blood and placental isolates were stained for a number of lymphoid cell markers by indirect immunofluorescence and analyzed by flow cytometry. Studies were performed on both freshly isolated mon onuclear cell preparations and in vitro cultured cells after selective expansion in interleukin 2 (IL2). Fresh placental mononuclear cell is olates were an average 20% CD3+; their CD4/CD8 ratios varied among ind ividuals. An average of 68% of the lymphocytes isolated from maternal peripheral blood were CD3+ Placental and maternal peripheral blood iso lates had comparable percentages of CD16+ and CD20+ cells, while CD56 cells were present at significantly greater numbers in the lymphocyte compartment of placenta (17%) than in peripheral blood (3%); P < 0.01 ). Lymphocyte isolates were expanded by culture with IL2 and PHA and s tained to determine if propagated lymphocyte populations are represent ative of initial isolates. Expansion of all lymphocyte isolates favore d CD3 phenotypes and CD8 phenotypes. Compared to expanded placenta-der ived populations, expanded peripheral blood lymphocytes were similar w ith regard to percentages of all phenotypes except gamma/deltaT cells which represented more of placental lymphocytes (10%) than peripheral lymphocytes (5%; P < 0.01). Surface HLA typing determined propagated p lacenta-derived lymphocytes to be of maternal and not fetal origin. In vitro propagation of placental mononuclear cell isolates may therefor e provide populations of maternal CD3+ lymphocytes for assessment of f unction and specificity.