Pregnancy-associated uterine granulated metrial gland cells in mutant and transgenic mice.
PROBLEM: Granulated metrial gland (GMG) cells are pregnancy-specific uterine lymphocytes found in rodents. The lineage relationships of GMG cells are incompletely defined, although genetic and immunophenotyping studies suggest membership in the natural killer (NK) cell lineage. Pregnancy-specific functions have been postulated for GMG cells, but no successful depletion of these cells has been achieved that would permit assessment of any critical roles that might influence gestational outcome. METHOD: Routine histological methods for light microscopy were used to assess implantation sites from wild-type mice and mice of the following genotypes: tgE26, mi/mi, and p53 knockout. RESULTS: GMG cells are transient, histamine-negative cells found in the pregnant uteri of most mice. Pregnancies in the NK and T-cell-deficient tgE26 were characterized by infrequent GMG cells, very small placentae, and an elevated rate of fetal and perinatal mortality. In term placentae of mi/mi with dystocia. GMG cells were found in a new location along the plane of placental separation, and they appeared degranulated. A normal life-history was observed for GMG cells in p53 knockout mice. CONCLUSION: Pregnancies in mutant and transgenic mice indicate that GMG cells are natural killer cells and have critical roles in placental development and pregnancy success. The disappearance of GMG cells at term is independent of p53 gene expression.