Immunosuppression by Progesterone in Pregnancy describes a newly discovered feto-protective mechanism resulting from the interaction of the immune and endocrine systems. As a response to antigenic stimulation by the fetus, lymphocytes of pregnant women develop non-classical progesterone receptors. Receptor binding of progesterone in the lymphocytes triggers the production of a mediator protein. Through an immunological pathway, this protein prevents abortion in murine models, and its serum concentration correlates with pregnancy outcome in humans. The regulation of these unusual receptors, as well as diagnostic and therapeutic implications of the mediator protein, are discussed. Immunologists, reproductive biologists, obstetricians, gynecologists, and other researchers studying this aspect of reproductive biology will find the book to be indispensable.