Placental HLA-G protein expression in vivo: where and what for?
In contrast to HLA-A and -B class Ia genes that are down-regulated in human trophoblast cells, HLA-G class Ib molecules are expressed in the placenta throughout gestation. In addition to extravillous cytotrophoblast that invade the decidua basalis essentially, HLA-G was also observed in endothelial cells of fetal vessels in the chorionic villi as well as in amnion cells and amniotic fluid. Both membrane-bound and soluble HLA-G isoforms have been detected. In view of the recently published functional data showing that HLA-G: (i) has the capability to bind and present peptides; (ii) is recognized by at least three different killing inhibitory receptors; and (iii) is a regulator of HLA-E expression, we can predict that such functions are likely to be exerted by extravillous cytotrophoblast. Of particular importance will be the anti-viral function of HLA-G at this materno-fetal interface, knowing that HLA-G was shown to be expressed by thymic medullary epithelial cells. In addition to these immunological functions, due to its presence on chorionic fetal endothelial cells, we hypothesize that HLA-G could also be a regulator of chorionic villous angiogenesis. Finally, soluble HLA-G isoforms may act as specific immunosuppressors during pregnancy.
Le Bouteiller
P
P
INSERM U395, CHU Purpan, Toulouse, France. Philippe.Le-Bouteiller@purpan.inserm.fr
Solier
C
C
Pröll
J
J
Aguerre-Girr
M
M
Fournel
S
S
Lenfant
F
F
D000653:Amniotic Fluid / Q000276:immunology / Q000378:metabolism; D002824:Chorionic Villi / Q000276:immunology / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D006680:HLA Antigens / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D059951:HLA-G Antigens; D015395:Histocompatibility Antigens Class I / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D006801:Humans; D008285:Major Histocompatibility Complex / Q000276:immunology* / Q000502:physiology; D010920:Placenta / Q000276:immunology* / Q000378:metabolism; D011247:Pregnancy; D020033:Protein Isoforms; D014327:Trophoblasts / Q000276:immunology / Q000378:metabolism
D006680:HLA Antigens; D059951:HLA-G Antigens; D015395:Histocompatibility Antigens Class I; D020033:Protein Isoforms