Reproductive Immunology from Copulation to Parturition in an Evolutionary and Ecological Context

Abstract

Female reproduction impacts whole-body physiology, ecology, and Darwinian fitness, as endocrine and physiological changes affect peripheral body systems and maternal behavior and compose the basis and constraints of reproductive success. In mammals, relative to males, females experience an even greater reproductive burden as a result of the dynamic hormonal and physiological shifts seen throughout pregnancy, lactation, and reproductive delays. The intersection between the reproductive and immune systems is particularly dynamic, as it fluctuates between cooperative interactions, such as when inflammation facilitates implantation and placentation, and opposing interactions, such as when the adaptive immune response is suppressed to avoid harm to sperm or the conceptus. These two systems share coevolved pathways and regulators that function to bring balance to maternal-offspring interactions. Maternal immune suppression throughout reproduction may exemplify potential trade-offs whereby suppression of the systemic immune system to protect the conceptus comes at a cost of maternal survival. Reciprocally, a robust immune response to protect maternal health may come at the cost of reproductive success. We outline the major cellular mechanisms of immune and reproductive interactions from copulation to parturition to help extrapolate fitness consequences. By addressing the effects of reproductive immunology on fitness, we discuss possible trade-offs that may exist, resulting from these interactions.