title: Altered phenotype of HLA-G expressing trophoblast and decidual natural killer cells in pathological pregnancies.
abstract: BACKGROUND
  The interaction between decidual natural killer (NK) cells and alloantigens expressed on fetal trophoblast cells are thought to be essential for successful implantation and placentation. Consequently, a disturbed interaction during the first trimester of pregnancy might well lead to a subsequent pregnancy failure.
  
  
  METHODS
  We investigated the expression of HLA-G and NK cell markers in tissue sections from recurrent miscarriage (n = 9) and ectopic tubal pregnancies (n = 5), and two hysterectomy specimens of healthy pregnancy as well as decidual biopsies (n = 9) were used as controls.
  
  
  RESULTS
  We show in normal pregnancy not only a decrease, but also a morphological change in CD56+ NK cells upon interaction with HLA-G-expressing trophoblasts. The cells appear to be transitioning from a blast-like (activation) state into a state of apoptosis. The number of CD16+ NK cells was low. In contrast, in recurrent miscarriage tissue a sustained NK cell marker expression of both CD56 and CD16 was paralleled by a decreased expression of HLA-G. No morphological changes from the blast-like stage were apparent. Finally, in ectopic pregnancies HLA-G expression in the absence of decidual NK cells was associated with a disturbed trophoblast differentiation.
  
  
  CONCLUSIONS
  In pathological pregnancies we show an in-situ altered phenotype of trophoblast and NK cells.
authors.affiliation: Department of Blood Transfusion and Transplantation Immunology, University Medical Centre Nijmegen, 6500 HB, Nijmegen, The Netherlands.
authors.forename: Peter M
authors.initials: PM
authors.lastname: Emmer
authors.forename: Eric A P
authors.initials: EA
authors.lastname: Steegers
authors.forename: Harold M J
authors.initials: HM
authors.lastname: Kerstens
authors.forename: Johan
authors.initials: J
authors.lastname: Bulten
authors.forename: Willianne L D M
authors.initials: WL
authors.lastname: Nelen
authors.forename: Kees
authors.initials: K
authors.lastname: Boer
authors.forename: Irma
authors.initials: I
authors.lastname: Joosten
mesh_terms: D000026:Abortion, Habitual / Q000235:genetics / Q000276:immunology*; D003656:Decidua / Q000276:immunology*; D005260:Female; D006680:HLA Antigens / Q000032:analysis*; D059951:HLA-G Antigens; D015395:Histocompatibility Antigens Class I / Q000032:analysis*; D006801:Humans; D016130:Immunophenotyping; D007694:Killer Cells, Natural / Q000276:immunology* / Q000502:physiology; D011247:Pregnancy; D011271:Pregnancy, Ectopic / Q000235:genetics / Q000276:immunology*; D012016:Reference Values; D014327:Trophoblasts / Q000276:immunology* / Q000502:physiology
chemical_list: D006680:HLA Antigens; D059951:HLA-G Antigens; D015395:Histocompatibility Antigens Class I