The expression of a novel natural killer inhibitory molecule, Cho-1, on the chorionic cytotrophoblast cells of successful pregnancy, but not of spontaneous abortion

The regulatory mechanism of the recognition and cytotoxicity by natural kil ler (NK) cells in placental tissue remains unclarified. Previous reports in dicated that monoclonal antibody Cho-1-defined molecule (Cho-1 molecule) ma y act as the negative regulator in the cytotoxicity by human NK cells. The Cho-1 molecule is composed of non-covalently asssociated cell surface molec ules of approximately 200 kDa and 40 kDa. In the present study we analyzed the expression of this novel molecule in extravillous cytotrophoblast cells , which are presumed to be exposed to the cytotoxic action by maternal NK c ells, from clinical cases of successful pregnancy and spontaneous abortion. By using monoclonal antibody Cho-1, our immunohistochemical data indicated that the Cho-1 molecule is clearly expressed in the cytotrophoblast cells of the early phase of successful pregnancy, but only weakly expressed in th ose from spontaneous abortion. The cytotrophoblast cells in the late phase (9-10 months) of pregnancy also expressed this molecule. Fluorescence-activ ated cell sorter analysis also showed that it is expressed on the cytotroph oblast cell surface of successful pregnancy but not on that of spontaneous abortion, suggesting that Cho-1 antigen may act as a negative regulator of the cytotoxicity by NK cells in successful pregnancy of the fetus.