Immunologic evidence for addition of oviductal components to the hamster zona pellucida

An indirect immunofluorescent procedure was used to determine whether zonae of unfertilized and fertilized eggs would bind antibodies specific for hamster reproductive tract antigens. Appropriate controls indicated that the fluorescent staining was probably due to antigen-antibody interactions. Antigens were not detected in zonae of ovarian eggs. However, components in zonae of unfertilized eggs collected from the oviduct at metestrus, mid-diestrus, and late diestrus bound antibodies specific for oviductal and uterine antigens. The antigens appeared to be concentrated in a peripheral band within the zona. An outer area of the zona around the eggs obtained from the uterus at proestrus also bound the antibodies, although the fluorescent staining was relatively faint. Antigens were observed in the peripheral area of zonae of fertilized eggs collected from oviducts on days 1 and 2 postcoitum. However, the antibody-binding component of the zona was noticeably reduced in embryos taken from the uterus on day 3 of pregnancy. The results are consistent with the idea that the zonae of both unfertilized and fertilized hamster eggs are composed of layers and that the outer region contains specific antigens which are dereived from the oviduct. Furthermore, loss or alteration of these components in the zona of an embryo (but not of an unfertilized egg of the same postovulation age) may reflect some chemical or structural change which is a prerequisite for zona shedding. Anti-uterus sera (unabsorbed and absorbed) did not interfere with zona removal by trypsin, indicating that the antigens detected in the present study are different from the receptor sites which bind anti-ovary antibodies and certain plant agglutinins (as reported by other workers).