Prolonged gestation does not extend survival of uterine Natural Killer lymphocytes in mice deleted in the receptor for prostaglandin F2 alpha

During decidualization in mice and women, expansion of the Natural Killer ( NK) cell lineage occurs within the uterus. In rodents, peak numbers of uter ine (u)NK cells are reached at mid-gestation. The population then declines and residual cells are shed with the placenta. Decidualization, but not a f etus, is required to induce division and maturation of uNK cells. Mechanism s regulating the decline in uNK cells are unknown. To determine if the conc eptus or its products have regulatory roles on uNK cell survival during nor mal gestation, a histological time course study was undertaken of implantat ion sites in mice ablated in the gene for the Prostaglandin F2 alpha recept or (PGF2 alpha R). These females experience normal gestation but fail to in itiate labour and delivery. Their pregnancies extend a further 4-7 days bef ore onset of maternal compromise. Large numbers of uNK cells were present i n PGF2 alpha R null mice by gestational day (gd) 10 and numbers had begun t o decline at gd 14. By gd 18, very few uNK cells remained and no uNK cells were found at day 22 of extended gestation. Thus, the population history of uNK cells in PGF2 alpha R null mice resembles that of uNK cells in normal mice, suggesting that the placenta, its products, the fetus and PGF2 alpha are not factors that influence the rate of uNK cell decline in late gestati on. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.