In this study, we identify molecular mediators that participate in the regulation of the immune response during corticosterone-induced stress in chickens. At 7 weeks of age, 120 chickens were exposed for 1 week to corticosterone treatment. Cytokine and chemokine mRNA expression levels were evaluated in peripheral blood and splenic lymphocytes. Expression levels of interleukin (IL)-1beta, IL-6, IL-18 and transforming growth factor (TGF)-beta4 mRNA were significantly up-regulated in lymphocytes 3 h after first treatment with corticosterone. TGF-beta4 and IL-18 remained elevated 1 week post-initial treatment. Compared with controls, corticosterone-treated birds showed greater expression levels of chemokine (CC) mRNA, particularly for CCLi2, CCL5 (RANTES), CCL16 and CXCLi1, in peripheral and splenic lymphocytes 3 h post-initial exposure. CCLi2 mRNA was highly expressed in splenocytes at all time-points. Administration of corticosterone significantly increased circulating corticosterone concentrations and decreased total lymphocyte counts at 3, 24 h and 1 week post-initiation of corticosterone treatment. There was a positive correlation between plasma corticosterone concentrations and CCL5 and CCL16 mRNA at 3 h post-initial administration. At 1 week post-initial treatment, corticosterone concentrations correlated positively with CCL5 and negatively with IL-18 mRNA level. Conditions associated with significant changes in corticosterone levels might therefore affect the immune response by increasing pro-inflammatory responses, leading to potential modulation of the Th1/Th2 balance.
