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Uterine natural killer cells: a specialized differentiation regulated by ovarian hormones

Authors

  • B. Anne Croy,

    Corresponding author
    1. Department of Anatomy and Cell Biology, Research Group in Reproduction, Development and Sexual Function, Queen’s University, Kingston, ON, Canada.
      Dr. B. Anne Croy
      Department of Anatomy and Cell Biology
      Room 924, Botterell Hall
      Queen’s University
      Kingston, Ontario, Canada K7L 3N6
      Tel.: 1-613-533-2859
      Fax: 1-613-533-2566
      E-mail: croya@post.queensu.ca
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  • Marianne J. Van Den Heuvel,

    1. Department of Pediatrics, Child Health Research Institute, University of Western Ontario, London, ON, Canada.
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  • Angela M. Borzychowski,

    1. Nuffield Department of Obstetrics and Gynaecology, University of Oxford, John Radcliffe Hospital, Oxford, UK.
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  • Chandrakant Tayade

    1. Department of Biomedical Sciences, University of Guelph, Guelph, ON, Canada.
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Dr. B. Anne Croy
Department of Anatomy and Cell Biology
Room 924, Botterell Hall
Queen’s University
Kingston, Ontario, Canada K7L 3N6
Tel.: 1-613-533-2859
Fax: 1-613-533-2566
E-mail: croya@post.queensu.ca

Abstract

Summary:  In adult females of many species, a transient population of natural killer (NK) cells appears in cycles within the uterine endometrium (lining). Appearance of these lymphocytes coincides with specific phases of the ovarian hormone cycle and/or early pregnancy. Studies in rodents, women, and pigs dominate the literature and suggest the uterine (u)NK cells are an activated subset sharing many but not all features with circulating or lymphoid organ-residing NK cells. During successful murine pregnancy, uNK cells appear to regulate initiation of structural changes in the feed arterial systems that support maternal endometrial tissue at sites of implantation and subsequent placental development. These changes, which reverse after pregnancy, create a higher volume arterial bed with flaccid vessels unresponsive to vasoactive compounds. These unique pregnancy-associated arterial changes elevate the volume of low-pressure, nutrient-rich, maternal arterial blood available to conceptuses. Regulation of the differentiation, activation, and functions of uNK cells is only partially known, and there is lively debate regarding whether and how uNK cells participate in infertility or spontaneous abortion. This review highlights the biology of uNK cells during successful pregnancy.

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