Laurence Melen

Lymphoid cell apoptosis induced by trophoblastic cells: a model of active foeto-placental tolerance

To test the hypothesis that CD95-L (Fas-L) present on trophoblastic cells plays a part in establishing foeto-placental tolerance by inducing apoptosis of immune defence cells, we cocultured trophoblasts with lymphoid cells and scored the frequency of cell death in these cultures. We prepared human trophoblastic cells from term placentas removed by C-section and placed them in culture for 48 h before introducing the lymphoid cells. We added Jurkat cells, a CD3 + lymphoid cell line, or purified T cells from human blood to the cultured trophoblasts and monitored apoptosis by electron microscopy and flow cytometry after TUNEL or annexin V labelling. The frequency of cell death in the CD3 + cell population was higher when the lymphoid cells were cocultured with trophoblastic cells than when they were cultured alone. This frequency increased with time but was reduced when anti-CD95-L antibodies were added to the culture medium. Cell death was less frequent in the lymphoid cell population when trophoblasts were replaced with human fibroblasts not expressing CD95-L.

Both pituitary and placental growth hormone transcripts are expressed in human peripheral blood mononuclear cells (PBMC)

The hGH‐V gene codes for a variant of human pituitary growth hormone (hGH‐N) named placental growth hormone (hPGH). hPGH shares 93% amino acid identity with hGH‐N. Until now the hGH‐V gene was considered to be exclusively expressed in human placenta, where it replaces maternal circulating hGH‐N at the end of pregnancy. In this study we investigated by reverse transcriptase‐polymerase chain reaction (RT‐PCR) analysis hGH‐N, and hGH‐V, gene expression in PBMC in men, women and pregnant women. We have demonstrated that hGH‐N and hGH‐V transcripts are simultaneously produced by PBMC in both men and women as well as pregnant women. The PBMC of a PIT‐.1‐negative woman expressed only the hGH‐V transcript, but not the hGH‐N one as expected. In conclusion, hGH‐V mRNA is expressed by cells other than the syncytiotrophoblast, is not regulated by PIT‐1, and may be involved in immune regulation, as is pituitary GH.