Decidual Natural Killer Cytotoxicity Decreased in Normal Pregnancy but Not in Anembryonic Pregnancy and Recurrent Spontaneous Abortion

PROBLEM: The natural killer (NK) cell activity is depressed in the decidua of early normal pregnancy. Recently Morii et al. (Am J Reprod Immunol 1993;29:1–4) found that all early intradecidual CD3 + T cells expressed either T cell receptor (TCR) α/β or γ/δ but that the expression of the CD3 + /TCR complex was down‐regulated. METHOD: To test whether these changes in decidual cellular immunity are different among normal pregnancy, anembryonic pregnancy and recurrent spontaneous abortion, we examined the immune cell subpopulations in the decidua from these three types of pregnancy using flow cytometry and an NK cytotoxicity assay. RESULTS: Intradecidual CD3 + T cells expressed either TCR α/β or γ/δ, and the level of expression of the CD3/TCR complex was down‐regulated in normal pregnancy, anembryonic pregnancy, and recurrent spontaneous abortion. Although the relative proportion of decidual NK cells was increased to approximately the same extent in all three types of pregnancy, decidual NK activity was higher in anembryonic pregnancies and in recurrent spontaneous abortions than it was in normal pregnancies. CONCLUSION: Decidual NK cell responses are different in anembryonic pregnancies and in recurrent spontaneous abortions than in normal pregnancies. Whether this difference is pathogenic or is the response to a dead embryo remains to be elucidated. 1995 Munksgaard