EXPRESSION OF THE NONCLASSIC HISTOCOMPATIBILITY ANTIGEN HLA-G BY PREECLAMPTIC PLACENTA

OBJECTIVE: Expression of the histocompatibility antigen HLA-G may be r equired for appropriate invasion and remodeling of uterine spiral arte ries. Inappropriate expression of this antigen may result in failure o f invasion, leading to partial placental ischemia and gestational dise ase. STUDY DESIGN: To test the hypothesis that the level of expression of HLA-G is reduced in trophoblasts from patients with gestational co mplications (preeclampsia, intrauterine growth retardation, or gestati onal hypertension) compared with patients with normal pregnancy, total ribonucleic acid was isolated from the fetal membrane or decidual int erface of term placenta from several patient groups. Ribonuclease prot ection assay was used to determine levels of HLA-G expression, which w as normalized for total ribonucleic acid input with beta-actin and for trophoblast content in the tissue by cytokeratin 8. RESULTS: When nor malized for total ribonucleic acid input (beta-actin), term placental expression of HLA-G was reduced for all forms of preeclampsia but not for intrauterine growth retardation or gestational hypertension. When tissue expression of cytokeratin, an indicator of trophoblast input, w as normalized for total ribonucleic acid input, primary preeclampsia a nd intrauterine growth retardation had reduced numbers of trophoblast per unit tissue. When controlled for trophoblast input HLA-G expressio n was similar to normal for all clinical groups, except for intrauteri ne growth retardation, which was slightly increased. CONCLUSION: Level of expression of HLA-G in placental tissue was reduced in preeclampsi a. This decrease in expression appears to be related to reduced number s of trophoblasts in placental tissue examined at term from patients w ith primary preeclampsia.