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Publisher Summary This chapter focuses on pregnancy-associated antigens in early pregnancy in the ewe. The establishment of pregnancy, in the first few weeks after mating, requires an immunological tolerance of the embryo by the mother and endocrine changes to facilitate implantation and the nutrient supply to the developing embryo. The chapter describes the detected presence of pregnancy-associated substances in the sheep using immunological techniques and discusses their role in early pregnancy. The activity of the rabbit antisera, as detected by immunofluorescence, can be removed either by absorption with an homogenate of uterus from ewes at day 15 of pregnancy, with an homogenate of 15–17 day old sheep embryos, or with erythrocytes from ewes between day 10 and day 15 of pregnancy. Antisera can provide a simple test for pregnancy-hemagglutination of erythrocytes indicating a positive test for pregnancy. There are several possible functions for the pregnancy-associated antigens. Even though the antigens or similar cross-reacting antigens are found in the uterus of some nonpregnant ewes, it remains possible for the pregnancy antigens to be involved in the prolongation of the life span of the corpus luteum in early pregnancy. |
