HLA-G expression in extravillous trophoblasts is an intrinsic property of cell differentiation: a lesson learned from ectopic pregnancies

Abstract

Human leukocyte antigen (HLA)-G is a major histocompatibility gene expressed almost exclusively in extravillous trophoblasts at the fetal-maternal interface. HLA-G may play a role in protecting the fetus from attack by the maternal natural killer cells. The extravillous trophoblasts invade the decidua and maternal spiral arteries. The factors which regulate the cell-specific expression of HLA-G are unknown. In this study we asked if HLA-G is expressed in extravillous trophoblasts that develop outside of their normal cellular environment, as in the case of ectopic pregnancies. Since all ectopic pregnancies implant in the absence of underlying decidua we also used a placenta accreta as an experimental control. We found that HLA-G mRNA and protein were expressed in the extravillous trophoblasts in the 13 ectopic specimens studied. In a case of placenta accreta (which develops without decidua basalis and is therefore adherent to the underlying myometrium), HLA-G mRNA and protein were also expressed. These results suggest that HLA-G expression is induced in a cell autonomous manner rather than determined by appropriate environmental cues.

A placental chorionic villous mesenchymal core cellular origin for infantile haemangioma

“…hPL is also expressed by trophoblasts, with the exception of cytotropholasts,21 and is responsible for the growth and development of the foetus during gestation 33. Likewise CK7 is a keratin filament type expressed in all trophoblast subpopulations,23 34 and HLA-G is a major histocompatibility gene expressed in the placenta throughout the three trimesters of pregnancy by trophoblast lineages 24…”

Altered expression of cellular membrane molecules of HLA-DR, HLA-G and CD99 in cervical intraepithelial neoplasias and invasive squamous cell carcinoma

“…Besides its selective physiologic placental localization, HLA-G has been found in HLA class I positive cells, such as thymic epithelial cells (Crisa et al, 1997), cytokine-activated monocytes (Moreau et al, 1999), and in some pathologic situations, such as pregnancy disorders (Goldman-Wohl et al, 2000), viral infections (Onno et al, 2000), transplantation (Lila et al, 2000), and tumors (Fukushima et al, 1998;Pangault et al, 2002). During the last few years several studies demonstrated that HLA-G molecules were only expressed in a few tumor cell lines (Pangault et al, 1999;Real et al, 1999;Frumento et al, 1999).…”

HLA-G in organ transplantation: towards clinical applications

“…Moreover, a reduced placental IL-10 production was observed in preeclampsia [54] and correlates with a low level of expression of HLA-G transcription [38,55]. On the other hand, the IL-10 homolog produced by cytomegalovirus (CMV) can up-regulate HLA-G protein expression at the monocyte cell surface and is supposed to participate in the mechanisms of escape of CMV to the immune system [56].…”