Immunolocalization of avian beta-defensins in the hen oviduct and their changes in the uterus during eggshell formation.

The aim of this study was to examine whether avian beta-defensin proteins (avbetaDs) exist in the oviduct, and whether those in the uterus are secreted to the eggshell membrane and eggshell. The oviducts of White Leghorn hens at different times of egg formation, eggshell membrane, and eggshell were used. The presence of immunoreactive (ir) avbetaD-3, -11, and -12 was examined by immunohistochemistry and western blot. Two or three types of avbetaDs were identified in the mucosal surface epithelial cells in each oviductal segment. The density of ir-avbetaD-3 and -12 in the uterus was decreased after the egg entered this segment. Western blot analysis confirmed the presence of ir-avbetaD-3, -11, and -12 in the uterus. In the eggshell membrane, only ir-avbetaD-3 was detected on the surface of fibers at the outer layer of the membrane. The ir-avbetaD-3, -11, and -12 were identified in the eggshell matrix by western blot. These results suggest that the surface epithelial cells are the major sites where avbetaDs proteins exist, and the avbetaDs secreted by the uterus cells are likely to be incorporated in the eggshell membrane and eggshell. These avbetaDs may play roles in the innate host defense of the oviduct and egg surface.