PHENOTYPIC CHARACTERIZATION OF NORMAL HUMAN PLACENTAL MONONUCLEAR-CELLS

The placenta is a rich source of immunocompetent cells. We have studie d the phenotype, number and origin of placental mononuclear blood cell s isolated from 32 normal term placentae using 4 color flow cytometry . Respective maternal and cord blood leucocyte preparations were also compared. Placental tissue without extraembryonic membranes was cut in to small pieces and divided. One portion was washed extensively with i ce-cold PBS. Both tissue portions were disrupted in a blender and cell s were dissociated by using a 180mu sieve. Leucocytes were isolated by Ficoll-Hypaque density gradient centrifugation. Maternal and cord blo ods were HLA typed and in cases of HLA-A2 or B7/40 disparity, monoclon al anti-HLA antibodies to these antigens showed that unwashed placenta l tissue contained 35% maternal and 65% fetal cells. This ratio, howev er, was not reflected for a given cell phenotype. In comparison, washe d placental tissue contained cells of fetal origin only. Both unwashed and washed placental tissue contained fewer CD3 and CD4, but more CD8 cells than maternal and cord blood. Markers of NK cells such as, CD16 , CD56, and CD57 showed this cellular phenotype to be 15 times more ab undant in the placental preparations than in cord and maternal blood. The quantitative differences between peripheral blood and placental CD 8 and NK cells were further explored with an antiprogesterone receptor antibody in combination with anti-CD8, anti-CD57 and anti-HLA-DR. The number of progesterone receptor (PGR) positive cells was three times higher in placental tissues than in cord or maternal blood. These data indicate that the phenotypic frequencies of certain placental leucocy tes are significantly different from maternal and fetal peripheral blo od. Progesterone and the presence of PGR may be important in the diffe rential retention of placental leucocytes.