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  • Title: Immunological aspects of sperm receptors on the zona pellucida of mammalian eggs.
    Author: Dunbar BS, Shivers CA.
    Journal: Immunol Commun; 1976; 5(5):375-85. PubMed ID: 61169.
    Abstract:
    Sperm receptor sites on the surface of the zona pellucida are believed to be necessary for fertilization on the mammalian egg. Ovary specific antibodies are known to precipitate the zona pellucida and are also responsible for inhibition of sperm binding and subsequent fertilization. The nature of the proposed receptor sites which are blocked by antibodies are discussed relative to comparable studies in which phytoagglutinins and other agents are used to determine the chemical nature of sperm receptor sites. The zona pellucida of the mammalian egg is a thick, transparent, noncellular structure surrounding the egg. It is formed in the ovary and is present until the time of implantation of the fertilized egg. The sperm must attach to and pass through it before making contact with the plasma membrane of the egg. The association of the sperm with the zona pellucida is species-specific. Sperm receptor sites on the surface of the zona pellucida are thought to be necessary for fertilization. Ovary-specific antibodies precipitate the zona pellucida and inhibit sperm binding, thus preventing fertilization. Some large molecules, such as immunoglobulins and ferritin, can penetrate the zona pellucida but some smaller molecules, such as heparin, cannot. The zona surface, as observed with the scanning electron microscope, is an irregular netlike structure with pores smaller than the sperm head. Biochemically it is a complex of sulfated acid and neutral micropolysaccharide and protein. Both of these components are antigenic. In some species, zona surface receptors that are involved in sperm attachment are protein components. Phytoagglutinins may be responsible for blocking hybrid fertilization. Immunological studies have shown that the hamster, mouse, and rabbit ovaries contain ovarian-specific antigens. By using immunofluorescent techniques, some ovarian antigens have been associated with the zona pellucida. Experiments using ovary-specific antigens have shown a precipitate on the outer region of the zona. This interaction renders attachment sites on the zona unavailable to the sperm. The antigenic properties of sperm binding sites of the zona pellucida may possibly be shown to be of use in contraception.
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