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.

Characterization of the regulatory functions of varicella-zoster virus open reading frame 4 gene product.

Varicella-zoster virus (VZV) open reading frame 4 (ORF4) encodes a protein with a predicted molecular weight of 51,540 presenting amino acid sequence homology with the immediate-early regulatory protein ICP27 of herpes simplex virus type 1. To investigate the regulatory properties of the ORF4 gene product, we performed a series of transient expression assays in Vero cells, using a plasmid expressing ORF4 as effector and several VZV genes and heterologous genes as targets. The VZV target plasmids contained promoter/regulatory regions from genes belonging to the three putative VZV kinetic classes fused to the chloramphenicol acetyltransferase (CAT) gene. The heterologous target plasmids consisted of promoter/regulatory regions of human cytomegalovirus, Rous sarcoma virus, and human immunodeficiency virus type 1 fused to the reporter gene. These experiments demonstrated that the ORF4 gene product activated expression of ORF62 in a dose-dependent fashion but had no effect on the expression of the three other putative immediate-early genes (ORF4, ORF61, and ORF63). When various amounts of ORF4 were transfected in the presence of early gene promoters, dose-dependent transactivation was evidenced with the thymidine kinase gene (ORF36) and the major DNA-binding protein gene (ORF29) promoters; interestingly, little activity was detected with the promoter of the DNA polymerase gene (ORF28). No activation of late gene expression, represented by the glycoprotein I and glycoprotein II genes, was seen even over a wide range of concentrations of input ORF4 plasmid. Expression of pCMVCAT, pRSVCAT, and pHIVCAT was also stimulated by the ORF4 gene product. CAT mRNA analysis showed that activation of VZV target promoters occurs at the transcriptional and/or posttranscriptional level.