Methods to produce stage-specific monoclonal antibodies against mouse trophoblast cells by intrasplenic and in vitro immunizations.

Monoclonal antibodies recognizing epitopes expressed by invasive mouse trophoblast cells were obtained by immunizing male mice of the NMRI strain with mouse egg-cylinders obtained by culturing blastocysts on agarose for 4 days. Immunization was achieved by intrasplenic and in vitro methods. The procedures described outline a rational way of producing and selecting antibodies which are stage-specific for the mouse trophoblast at implantation and early placentation. Preimplantation stage-specificity was tested and adhesive blastocysts only were detected by 4 antibodies. Thus, these antibodies become markers for that developmental stage which characterizes an adhesive blastocyst ready to implant. Postimplantation stage-specificity was demonstrated by 6 antibodies, which labelled trophoblast cells of day 7 implantations only. Thus, there is a specific expression of some epitopes by the invasive trophoblast. Cell surface epitopes were detected on adhesive blastocysts by 4 antibodies and on the invasive trophoblast of the egg-cylinder by 7 antibodies. Shedded antigens from egg-cylinders in vitro were detected by 5 antibodies. Four of these antibodies detected substances released only from early implantation stages. A functional effect was demonstrated for an IgM antibody which impaired hatching and outgrowth of blastocysts in vitro.