Immune competence involving the natural killer cell lineage promotes placental growth

Very small placentae and absence of uterine natural killer (uNK) cells are amongst the reproductive deficits found in the natural killer (NK) cell and thymus-derived (T) cell immunodeficient mouse tg epsilon 26. These defects can be reversed by grafting of adult tg epsilon 26 females with bone marrow from T and B cell immunodeficient scid/scid donors. We report here that a second protocol, grafting of neonatal tg epsilon 26 females with immunocompetent bone marrow pretreated with antibody to Thy-1, successfully established the uNK cell lineage and ameliorated the phenotype. Further, comparisons of mid-gestation (days 10-16) placental area measurements from tg epsilon 26 and seven other immunodeficient strains to time-matched tissues from four strains of immunocompetent mice indicate that lymphocytes of the NK but not the T or B cell lineages are able to influence placental size during normal gestation and that this action is independent of interleukin 2. Area measurements of placentae produced in manipulated tg epsilon 26 pregnancies (maternal bone marrow engraftment, outcrossing to immunocompetent males and reciprocal embryo transfers with an immunocompetent strain) suggest that NK cell competence is required in each of the maternal and fetal compartments to optimize placental growth. (C) 1999 W. B. Saunders Company Ltd.