Immunofluorescent localization of immunoglobulins on the cell surface of mouse oocytes and preimplantation embryos.

Living mouse oocytes and preimplantation embryos were assayed by indirect immunofluorescence for their ability to adsorb heterologous serum proteins from culture media to their cell surfaces. Bovine and human immunoglobulins of the IgG class were adsorbed by the oocytes and all stages of preimplantation embryos, while IgG of mouse or goat origin was not. In contrast, none of the serum albumins was adsorbed to the cell surfaces of mouse oocytes and preimplantation embryos. From the differential binding of IgG of some, but not all, of the species that were tested, we concluded that these cell surface IgG "receptors" on mouse oocytes and preimplantation embryos are likely to be heterophilic in nature. Similar observations were made irrespective of the strain of mice used to provide the oocytes and embryos. These observations raise the question of whether human oocytes and preimplantation embryos should also be assayed for their ability to adsorb animal serum proteins that are possible candidates as a substitute protein supplement for human serum in culture medium used in human in vitro fertilization/embryo transfer programs.