[The evolution of the natural-killer-dependent cytotoxic activity during normal pregnancy].

The fetus was compared to an allograft because paternal antigens are also expressed. Even the analogy is not a real one, the main steps of the rejection phenomenon are relevant for the understanding of the complex materno-fetal interactions as the large granular lymphocytes are the first immune cells which invade the graft. Due to the important role of NK cells in the cell mediated immune response, the purpose of this paper was to assess the NK cell dependent cytotoxicity during normal pregnancy. The study was performed on a test group of 52 normal gravidas, in the Ist, IInd and IIIrd trimester and a control group of 20 healthy nonpregnant women with similar age and parity averages. The cytotoxic activity of the NK cells was measured in a 51Cr release assay against K 562 cell line. The results were expressed as the cytotoxicity index (%) and showed a statistically significant decrease for all gravidas compared to controls, mostly for the IInd trimester. The trend of the NK cytotoxic activity during normal pregnancy suggests the deep involvement of the NK cells in the mechanisms acting at the fetomaternal interface.