IMMUNOLOGICAL EVIDENCE FOR THE EXPRESSION OF THE FAS ANTIGEN IN THE INFANT AND ADULT HUMAN OVARY DURING FOLLICULAR REGRESSION AND ATRESIA

Immunohistochemical localization of the Fas antigen in the infant and adult human ovary during follicular growth, regression, and atresia wa s examined by the avidin/biotin immunoperoxidase method with a monoclo nal antibody to the Fas antigen. Western blotting was used to confirm the presence of the Fas antigen protein. In primordial and primary fol licles within the normal adult ovary, only the oocyte showed moderate immunostaining for the Fas antigen. In secondary and antral follicles, only the oocyte showed weak staining for the Fas antigen, while in pr eovulatory follicles, neither the oocyte nor the granulosa and theca c ells were immunostained for the Fas antigen. In corpora lutea, the Fas antigen staining became apparent in the granulosa lutein cells during the early luteal phase and intensified during the mid luteal phase, w hile the theca lutein cells became positive for the Fas antigen staini ng during the mid luteal phase. During the late luteal phase, the stai ning intensity of the Fas antigen in the regressing corpora lutea furt her increased. As the regressing corpora lutea were converted into cor pora albicans, the staining intensity decreased, and the corpora albic ans and stromal cells were negative for the Fas antigen. In atretic pr imordial and primary follicles, only the degenerating oocyte showed th e Fas antigen staining. By contrast, in atretic antral follicles, the Fas antigen staining was profound in the degenerating granulosa cells at the early stage of atresia, and at the mid stage of atresia it was intensified in the cell surface of the scattered granulosa cells and b ecame apparent; in the theca cells. At the late stage of atresia the F as antigen remained only in the hypertrophied theca cells, In the infa nt ovary, only the oocyte in primordial and primary follicles exhibite d intense staining for the Fas antigen. In the postmenopausal ovary, t he Fas antigen staining was entirely negative. Western blot analysis r evealed the presence of the Fas antigen protein with a molecular mass of 45 kDa in luteal tissues. On the basis of the recent evidence, that the Fas antigen mediates an apoptotic signal in a variety of cells, t he abundant expression of the Fas antigen in the regressing corpora lu tea and atretic follicles suggests that the Fas antigen participates i n luteal regression and follicular atresia through the apoptotic proce ss. Furthermore, notable expression of the Fas antigen in the oocyte o f primordial and primary follicles within the infant and adult human o vary followed by the decrease in the Fas antigen expression in the ooc yte with the advance of follicular maturation suggests that the Fas an tigen expression in the oocyte may play a role in follicular selection .