Medawar redux - an overview on the use of farm animal models to elucidate principles of reproductive immunology.

Farm animals have been important models for the development of reproductive immunology. Two of the major concepts underpinning reproductive immunology, the idea of the fetal allograft and progesterone's role in regulation of uterine immunity, were developed using the bovine as a model. This volume of the American Journal of Reproductive Immunology is composed of review articles that highlight the continued relevance of farm animals as models for research in mammalian biology. It is important that a diverse array of genotypes are used to elucidate biological principles relevant to mammalian biology and human health because the nature of mammalian evolution has resulted in a situation where the genome of the most commonly used animal model, the laboratory mouse, is less similar to the human than other species like the cow. Moreover, the evolution of placental function has been accompanied by formation of new genes during recent evolution so that orthologs do not exist in any but closely related species. Given the infrastructure needs to study farm animal species, optimal utilization of these animals as models for biomedical research will require significant increases in funding to reverse a historical erosion of resources devoted to animal agricultural research.