Changes in the Localization of MHC Class II Positive Cells in Response to Salmonella enteritidis Invasion in the Ovary of Laying Hens

Abstract

Major histocompatibility complex class II (MHC-II) molecules play essential roles in the initiation of immune responses against pathogenic agents. Salmonella enteritidis (S. enteritidis) bacteria may contaminate hen eggs during their formation in the ovary. The goal of this study was to determine whether ovarian MHC-II+ cells respond to S. enteritidis. Laying hens were intraperitoneally injected with or without PBS (control) or S. enteritidis (5.0×109 bacteria/bird) and examined 12h after inoculation. Cryostat sections of ovarian stroma, small white follicles and preovulatory follicles were double-immunostained sequentially for the localization of MHC-II+ cells and S. enteritidis. The MHC-II+ cells were localized in the ovarian stroma and the theca layer of the stromal, small white and preovulatory follicles. S. enteritidis was detected in the stroma and the theca layer of all types of follicles 12h after inoculation. The frequency of MHC-II+ cells was significantly increased in the ovarian stroma and the theca of all types of follicles by S. enteritidis inoculation (P<0.01) but not by PBS injection. These results suggest that the population of MHC-II+ cells in ovarian tissues increases in response to S. enteritidis invasion for defending against them.