CHARACTERIZATION OF SPERMATOZOAL AUTO-, ISO- AND ALLO-ANTIGENS

Abstract

ABSTRACT Three approaches are utilized to study and characterize spermatozoal antigens. An immunological approach has demonstrated the presence of spermatozoal auto-, iso- and allo-antigens. Spermatozoal auto-antigens studied by several authors are able to induce the whole spectrum of immune reactions (delayed hypersensitivity, complement-fixing antibodies and anaphylactic antibodies) as well as of autoimmune aspermatogenic orchiepididymitis (AIAO). Different extraction procedures result in various preparations and even in different independent autoantigens (at least four), one protein, one membrane-linked antigen and at least two glycoproteins. Spermatozoal iso-antigens stricto sensu are determined by the Y chromosome and are present on at least 50 % of the spermatozoa. Spermatozoal allo-antigens are also present at the surface of spermatozoa, especially blood group antigens (ABO and MNS systems), transplantation antigens (HL-A, H-2) and also some other unidentified ones. A biochemical approach has mainly been directed towards spermatozoal enzymes that have been shown to be antigenic even in the species of origin. This is the case for lactic dehydrogenase LDH-X (a mid-piece enzyme) and for acrosomal enzymes, e. g., hyaluronidase, possibly sorbitol dehydrogenase and trypsin-like acrosomal proteinase (the auto- and allo-antigenicity of the latter having not been established). At least three of these enzymes are known or supposed to play a role in the process of fertilization. A clinical approach has described the presence of spermatozoal-coating antigen(s), such as transferrin or blood group substances from secretors obtained following the admixture of the secretions of the seminal vesicles. Indications were also obtained for the existence of antibodies directed against defined antigens. Several types of localization of antibodies on spermatozoa were described: acrosome (front part), equatorial segment, post-nuclear region, mid-piece and tail. Attempts at fractionation of human spermatozoal antigens are still at a preliminary stage. Whatever the approach, the main interest of these antigens is that they are able to induce, in the species of origin or in a related species, antibodies capable of interfering with the normal process of reproduction, especially fertilization. In view of possible applications in the male or in the female, a few immunological considerations are of primary importance, particularly the localization of antigens (and their accessibility at the spermatozoal surface), their biological necessity for the reproductive process, the passage of the immune agents from the intravascular compartment to the genital tract, the possibility of inducing local immunization as well as to be able to direct the immune reaction at will toward the formation of immune agents responsible for the rejection reaction (sensitized cells, complement-fixing antibodies and complement) or the facilitation reaction (facilitating antibodies or suppressive cells).