| The aims of study were to identify high (H), medium (M), and low (L) hypothalamic-pituitary-adrenal axis (HPAA) stress responsive sheep using E. coli endotoxin lipopolysaccharide (LPS), and to assess associations between variable stress responsiveness and immune responsiveness (IR), and hepatic gene expression. Sheep were challenged iv with LPS and identified as H, M, L stress responders based on their estimated breeding values for peak cortisol concentration 4-hours post-challenge. Liver biopsies were collected from the H and L responders for hepatic gene expression studies. Unexpectedly, the IR was not significantly different between H and L stress responders. However, there was a significantly higher cell-mediated IR and a lower antigen-specific primary IgG response (P ≤ 0.05) in H and L stress responders when compared to M stress responders. Similar hepatic gene expression profiles between the H and L HPAA responders suggests that hepatic gene expression doesn't contribute significantly to this stress response phenotype. |
