Expression of class I HLA genes by trophoblast cells. Analysis by in situ hybridization.
Evaluation of trophoblast cells by immunohistology has shown that subpopulations of trophoblast cells express class I HLA differently from one another and differently from embryonic and adult cells. Placental syncytial trophoblast does not express detectable levels of class I HLA; chorion membrane cytotrophoblasts bind one mAb to monomorphic determinants of class I Ag, W6/32, but not a second, 61D2. In the present study, sections of normal term placentae and matching extraplacental membranes were evaluated by in situ hybridization procedures for cells containing class I HLA mRNA using pHLA1.1, which is complementary to HLA-B. Class I Ag expression was identified by immunohistology using two mAb to class I HLA (W6/32, 61D2) and the mAb 4E to identify HLA-B. Placental syncytial trophoblast contained low to undetectable levels of class I mRNA and failed to bind all three mAb. Chorion membrane cytotrophoblast cells contained moderate levels of class I HLA mRNA and were positive with the mAb W6/32 but were negative with 61D2 and 4E. In adjacent tissues, fetal mesenchymal cells and maternal decidual cells contained high levels of class I mRNA and were positive with all three mAb. The results suggest that syncytial trophoblast may not express class I HLA because of low steady-state levels of class I HLA mRNA. In contrast, chorionic cytotrophoblast cells may express truncated versions of class I HLA or nonclassical HLA-A,B,C-like Ag. Regulation of the expression of class I HLA gene products may be essential to the development of a satisfactory immunologic relationship between the mother and her semiallogeneic fetus during pregnancy.
D000911:Antibodies, Monoclonal / Q000378:metabolism; D002823:Chorion / Q000276:immunology / Q000378:metabolism; D005260:Female; D005805:Genes, MHC Class I; D006680:HLA Antigens / Q000096:biosynthesis* / Q000235:genetics; D006801:Humans; D007124:Immunoenzyme Techniques; D009693:Nucleic Acid Hybridization; D010920:Placenta / Q000276:immunology / Q000378:metabolism; D011247:Pregnancy; D012313:RNA / Q000235:genetics; D016372:RNA, Antisense; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D014327:Trophoblasts / Q000276:immunology* / Q000378:metabolism
D000911:Antibodies, Monoclonal; D006680:HLA Antigens; D016372:RNA, Antisense; D012333:RNA, Messenger; D012313:RNA