Identification of class I MHC mRNA in human first trimester trophoblast cells by in situ hybridization.
Special gestation-related regulatory mechanisms for the expression of class I Ag by trophoblast cells directly exposed to maternal blood and tissues may be required for semiallogeneic pregnancy to be successful. Analysis of class I MHC mRNA by in situ hybridization and class I MHC Ag by immunohistology has revealed two phenotypically distinct subpopulations of trophoblast cells in term placentas and extraplacental membranes. Trophoblast cells external to the placenta are mRNA +/Ag+. They contain class I mRNA and express class I Ag that differ serologically from HLA-A,B,C. In contrast, trophoblast cells forming the syncytial layer of placental villi are mRNA-/Ag-. By immunohistology, trophoblast cells in 1st trimester placental tissues are similar to those in term tissues. In our study, in situ hybridization was used to determine if patterns of trophoblast cell class I mRNA were the same or different. Trophoblast cells external to the placental villi in 1st trimester tissues contained class I mRNA as would be predicted from the results with term tissues. Unexpectedly, class I mRNA was found in villous trophoblast cells. Thus, these studies identified an mRNA+/Ag- trophoblast cell subpopulation. The results suggest that tissue-specific mechanisms may interfere with translation of class I mRNA in 1st trimester villous trophoblast cells and/or that the protein products of the mRNA are not identified by available mAb.
Hunt
J S
JS
Department of Pathology, University of Kansas Medical Center, Kansas City 66103.
Fishback
J L
JL
Chumbley
G
G
Loke
Y W
YW
D005260:Female; D015870:Gene Expression; D015395:Histocompatibility Antigens Class I / Q000235:genetics*; D006801:Humans; D009693:Nucleic Acid Hybridization; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D012333:RNA, Messenger / Q000235:genetics; D014327:Trophoblasts / Q000166:cytology / Q000502:physiology*
D015395:Histocompatibility Antigens Class I; D012333:RNA, Messenger