Date of Award
Doctor of Philosophy (PhD)
A developing oocyte is capable of synthesizing "non-self" proteins recognized as foreign by the maternal immune system. Since the oocyte may be perceived as foreign it must be protected from interaction with the immune system in order for it to mature to the point of ovulation. Oocytes that begin development but do not mature to the point of ovulation become atretic and are destroyed and phagocytized by the maternal system. This study proposes that the zona pellucida of the ovarian follicle is the barrier between the immune system and the oocyte. The suggestion is made that the oocyte may play a role in blocking the immune system during its maturation, and follicles in which the oocyte is incapable of providing for its own protection become atretic.
Indirect immunolabelling techniques employing both peroxidase and fluorochrome-conjugated antibodies were used to assess the presence of immunoglobulin G, female protein, and albumin in the ovary of the golden hamster Mesocricetus auratus. This experimental technique indicates that immunoglobulin G, female protein, and albumin are found localized in the zona pellucida and liquor folliculi of ovarian follicles.
Intravenous injection of fluorescein-conjugated hamster immunoglobulin G demonstrates the ability of the zona pellucida to limit access of serum immunoglobulin G to the oocyte. The labelled immunoglobulin G circulates rapidly through the animal and does not appear to be impeded in its access to the follicle. It accumulates rapidly in the liquor folliculi and zona pellucida yet never appears within the perivitelline space.
The results of this study suggest that the zona pellucida is responsible for separating the developing oocyte from the maternal immune system, thus forming a "blood-oocyte" barrier to immunoglobulins. Further speculation is made that the oocyte plays a role in its own protection by production of factors capable of blocking complement fixation. If incapable of providing for its own protection, the oocyte is acted upon by the maternal immune system. The zona pellucida and liquor folliculi aid the immune system by providing an area for local storage of proteins necessary to accomplish complement fixation and subsequent follicular atresia.
Forsman, Allan D., "The Blood-Oocyte Barrier: Morphological Evidence Implicating The Zona Pellucida" (1991). Theses and Dissertations. 984.