Regulation of the maternal immune system during early bovine pregnancy.

A cow's ability to produce a live calf every year is critical for profitable and sustainable cattle production, but immunological rejection of the embryo, resulting in pregnancy complications or loss, is a significant obstacle. The fundamental role of the immune system is to recognize antigens, or foreign molecules, in the body and induce an inflammatory response against these antigens to protect the host animal. Pregnancy represents an immunological paradox in which the maternal immune system not only tolerates the semi-foreign embryo, which contains paternal antigens, but creates a uterine environment supportive of its survival and development. Immune responses during pregnancy are tightly regulated to balance the need for tolerance of the embryo with the need for protection against pathogens. This literature review explores the regulatory mechanisms used to prevent the maternal immune system from attacking the semi-foreign embryo and describes the consequences of immunological dysregulation during bovine pregnancy.