2005 Volume 42 Issue 2 Pages 101-109
The aim of this study was to determine whether the expressions of MHC class I and II in the ovarian follicles change with follicular growth and aging of birds. Theca layer of white follicles (WF), the largest and the third largest preovulatory follicles (F1 and F3, respectively) and the largest postovulatory follicle (POF) were collected from laying hens. Localization of MHC class I and II cells was examined by immunocytochemistry. Changes in the MHC class I and II mRNA expressions in the theca were examined by semi quantitative RT-PCR. MHC class I+ cells were observed mostly in the theca interna of WF, F3, F1 and POF, whereas MHC class II+ cells were observed in both theca interna and externa of those follicles. In addition, MHC class II+ cells were observed not only in theca layer but also in granulosa layer in POF. The expression level of MHC class I mRNA was similar in the theca layers among WF, F3, F1 and POF within young and old birds as well as between young and old birds within each type of follicles. The expression level of MHC class II mRNA was significantly lower in old birds than in young birds (P<0.01). However, there was no significant difference in that level among the follicles within young and old hens. These results suggest that the expressions of MHC class I and II may not be changed with follicular growth, whereas the expression of MHC class II is declined with age in the theca layer.