Changes in the Expression of Avian β-defensins (AvBDs) and Proinflammatory Cytokines and Localization of AvBD2 in the Intestine of Broiler Embryos and Chicks during Growth

The aim of this study was to determine the changes in the expression of avian β-defensins (AvBDs) and proinflammatory cytokines and localization of AvBD2 in the intestine of broiler embryos and chicks during growth.The ileum and cecum of embryonic day 19 (ED19) and of day-old (D0) and 7-day-old (D7) chicks were collected.Gene expression levels of 10 AvBDs (AvBD1-8, 10, and 12) and proinflammatory cytokines (IL-1β, -6, and -8) were analyzed using real-time PCR, and the localization of AvBD2 was examined by immunohistochemistry. Gene expression levels of AvBD1, 2, 6, and 7 in the ileum and of AvBD1 and 4 in the cecum were higher on ED19 than on D7.The expression of AvBD10 in the ileum was higher on D0 than on ED19, whereas the expression levels of AvBD8 and 10 in the cecum were higher on D0 than on ED19, and that of AvBD10 decreased on D7.The expression levels of IL-1β, -6, and -8 in the ileum were higher on D7 than on ED19.The expression levels of IL-1β, -6, and -8 in the cecum were higher on D0 than on ED19, and that of IL-1β and -6 declined on D7.AvBD2-positive cells were localized in the lamina propria beneath epithelial cells of villi and crypts.The number of positive cells in the cecum mucosa was greater on D0 than on ED19 and D7.In conclusion, we suggest that AvBDs are expressed in the ileum and cecum of embryos and chicks at high levels before or just after hatching and decrease by D7.The expression of proinflammatory cytokines in the ileum increases with growth until D7, but is the highest in the cecum around hatching.These AvBDs and proinflammatory cytokines may play roles in host defense in the intestinal mucosa of embryos and neonatal chicks.