Expression of maternal and paternal antigens on trophoblast

Abstract

GENETICALLY different individuals will not usually accept tissue grafts from one another. The best known exception to this is the ability of the foetus to act as a homograft. Fertilised mouse eggs contain both paternally and maternally derived antigens^1,2, but it has not so far been demonstrated whether paternal antigens are expressed on mouse trophoblast, the embryo tissue which forms initial contact with the maternal circulation. If present, such antigens may be masked by a mucopolysaccharide³; this has been disputed by Simmons et al.⁴. Alternatively, it has been proposed that trophoblast lacks transplantation antigens⁵ and Searle et al.⁶ failed to immunise a recipient with mouse trophoblast when tested either by skin grafting or cell-mediated cytotoxicity. It has been suggested, however, that histocompatibility antigens on human trophoblast were responsible for cytotoxic antibody found in the sera of 12-week human pregnancies⁷, and Nakakita showed antibody production in mice to human trophoblast, using immune adherence⁸. I now report the presence of both paternal and maternal antigens on trophoblast outgrowths of mouse blastocysts in vitro.