For 20 years our program has focused on the biological interactions that take place between a mother and fetus during pregnancy. In particular, we are concerned with how the placenta and fetus avoid recognition and destruction by the maternal immune system. This is an intriguing question that has broad applications to many areas of biology and medicine, including organ transplantation and cancer biology. In the course of these studies our laboratory has acquired expertise in three important areas of equine medicine: immunology, genetics, and reproduction. The immunological assays we have developed for our research are also used to characterize immune system defects in horses admitted to the Large Animal Hospital at Cornell. Our reproductive studies have led to new ways to study the growth and function of the placenta. Finally, our genetic studies have been fundamental to the international collaboration of the Horse Genome Project.