IMMUNOLOGICAL SUPPRESSION OF REPRODUCTIVE FUNCTIONS IN MALE AND FEMALE MAMMALS

Fertility control is an important aspect of management in farm, domestic and recreational animals, and is also of importance in man. Traditional surgical procedures of sterilisation are generally irreversible in animals. This is desirable in livestock not required for breeding, whereas in domestic and recreational animals reversible techniques would in some instances be an advantage. Immunological approaches to fertility control have recently emerged as alternatives to surgical procedures. Immunological control of reproductive function can be directed at reproductive hormones, gamete antigens and the conceptus. The site within the reproductive axis at which immunological intervention is directed depends on whether it is desirable to suppress overall sexual function, or only conception. In livestock, it is often necessary to suppress sexual and aggressive behaviour and hence attention has focused on immunological neutralisation of reproductive hormones that drive these behaviours. Hormones that have been targeted include luteinising hormone releasing hormone, luteinising hormone and gonadal steroids. In circumstances where the maintenance of sexual functions is required but conception blocked, the focus has been on follicle stimulating hormone, chorionic gonadotrophins (man) surface antigens on sperm and the zona pellucida and the conceptus. A range of sperm surface antigens, some of which appear species-specific, have been identified and are undergoing intense study for contraceptive vaccines. Immunological approaches to fertility control are non-invasive and have the further advantage of reversibility.