title: HLA-G is expressed by the glandular epithelium of peritoneal endometriosis but not in eutopic endometrium.
abstract: BACKGROUND
  HLA-G is a major histocompatability antigen with documented immune-regulatory function. Various epithelial cancers and tissue allografts have been noted to express HLA-G, which is postulated to aid in their escape from immunosurveillance. We evaluated peritoneal endometriosis and eutopic endometrium for the expression of HLA-G protein and gene transcript.
  
  
  METHODS
  Two experiments were performed: (i) archived tissue blocks from peritoneal endometriotic lesions (n = 15) and eutopic endometrium (n = 12) were evaluated for extent of protein immunostaining, and (ii) eutopic endometrial biopsies from women without (n = 17) and with (n = 24) endometriosis, and peritoneal endometriotic lesions (n = 14) were evaluated for presence of RNA transcript by in situ hybridization.
  
  
  RESULTS
  HLA-G protein localized in the glandular epithelium of 14 of 15 (93.3%) peritoneal endometriotic lesions, but not in stromal cells. HLA-G protein staining was absent in endometrial biopsies (n = 12). HLA-G gene transcript localized to the glandular epithelium in 13 of 14 (92.8%) peritoneal endometriotic lesions. HLA-G transcript was never observed in eutopic endometrium, regardless of cycle stage or whether from women with (n = 24) or without (n = 18) endometriosis.
  
  
  CONCLUSIONS
  HLA-G is expressed by endometriotic glandular epithelium but not by eutopic endometrium under normal conditions. Differential expression of HLA-G suggests that peritoneal inflammation or cellular stress may up-regulate mechanisms to promote ectopic endometrial survival.
authors.affiliation: Department of Obstetrics, Gynecology and Women's Health, Division of Reproductive and Perinatal Research, University of Missouri-Columbia, Missouri 65212, USA. barrierb@health.missouri.edu
authors.forename: B F
authors.initials: BF
authors.lastname: Barrier
authors.forename: B S
authors.initials: BS
authors.lastname: Kendall
authors.forename: C E
authors.initials: CE
authors.lastname: Ryan
authors.forename: K L
authors.initials: KL
authors.lastname: Sharpe-Timms
mesh_terms: D001706:Biopsy; D004715:Endometriosis / Q000276:immunology* / Q000473:pathology; D004717:Endometrium / Q000276:immunology* / Q000473:pathology; D004848:Epithelium / Q000276:immunology / Q000473:pathology; D005260:Female; D006680:HLA Antigens / Q000235:genetics / Q000378:metabolism*; D059951:HLA-G Antigens; D015395:Histocompatibility Antigens Class I / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D010532:Peritoneal Diseases / Q000276:immunology* / Q000473:pathology; D012313:RNA / Q000378:metabolism
chemical_list: D006680:HLA Antigens; D059951:HLA-G Antigens; D015395:Histocompatibility Antigens Class I; D012313:RNA