Permeability of the mouse zona pellucida to immunoglobulin

During the preimplantation stages of pregnancy, the mammalian embryo is surrounded by an acellular envelope, the zona pellucida. Although little is known of the functions of this membrane it has been suggested that it may be impermeable to antibody molecules (immunoglobulins), thereby protecting the embryo from the potentially adverse effects of maternal immunity (Simmons & Russell, 1966, 1967). In the present study, we have investigated the permeability ofthe mouse zona pellucida to immunoglobulins by comparing the complement-mediated cytotoxic effect of rabbit anti-mouse serum and two of its immuno-globulin components, IgG and IgM, on the development of zona-free and zona-enclosed embryos in vitro. Mouse embryos at the 8-cell stage were recovered in phosphate-buffered saline (PBS) from the oviducts of randomly bred hybrid mice 48 hr after the finding of a vaginal plug. Half of the embryos were left with the zona pellucida intact, and the other half were transferred to 0\m=.\5 % pronase in PBS and in-cubated at 37\s=deg\C until partial digestion of the zona occurred, when removal wa