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


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


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.