Sperm Autoantigens and Fertilization: II. Effects of Anti-Guinea Pig Sperm Autoantibodies on Sperm-Ovum Interactions

Abstract

Bivalent (IgG) and monovalent (Fab) antibodies isolated from antisperm autoantiserum of the guinea pig were tested for their effects on the penetration of guinea pig zona pellucida by acrosome-reacted guinea pig spermatozoa and the fusion of acrosome-reacted guinea pig spermatozoa with plasma membranes of guinea pig and hamster ova. In the presence of antiserum IgG, acrosome-reacted spermatozoa appeared as single, highly motile cells. They were completely prevented from interacting with guinea pig zona and from fusing with zona-free hamster ova, while their fusion with zona-free guinea pig ova was markedly inhibited. These cellular interactions were blocked, to a lesser degree, by monovalent (Fab) antibodies isolated from the same antisperm antiserum. IgG or Fab from normal guinea pig sera had no effect on these cellular interactions. Pretreatment of ova with antisperm IgG or Fab did not interfere with the interaction of ova with untreated acrosome-reacted spermatozoa. Evidently, autoantigenic molecules on the surface and/or an intracellular membrane (e.g., the inner acrosomal membrane) of spermatozoa may be involved in the recognition of complementary ligands on the ova during the process of sperm-zona and sperm-vitellus interaction. Blockage of these cellular events in fertilization by antireceptor antibodies is a potential mechanism whereby immune responses to sperm-specific antigens can render females infertile.