Intravenous Infusion of Cortisol, Adrenaline, or Noradrenaline Alters Porcine Immune Cell Numbers and Promotes Innate over Adaptive Immune Functionality.

Despite the importance of pigs (Sus scrofa domestica) in livestock production and their increasing role as a model organism for human physiology, knowledge about the porcine immune system under the influence of stress hormones is fragmentary. Exceptionally little is known about the effects of catecholamines. Therefore, the aim of this study was to examine the in vivo effects of adrenaline, noradrenaline, and cortisol on number and functionality of porcine blood immune cells. Castrated male pigs (n = 34) were treated with physiological doses of either adrenaline, noradrenaline, or cortisol via i.v. infusion for 48 h. Blood samples were collected before treatment (-24 h, -22 h, 0 h), during treatment (+2 h, +24 h, +48 h), and at 72 h postinfusion. Immune cell numbers and phagocytic activity were evaluated by flow cytometry and lymphocyte proliferation by 3H-thymidine incorporation. Total IgG and IgM Ab levels were determined via ELISA. Pigs receiving cortisol showed strongly decreased adaptive immune cell numbers and increased neutrophils, accompanied by hampered lymphocyte proliferation but increased monocyte phagocytosis. Catecholamine effects on immune cell numbers were mostly similar to cortisol in direction but smaller in intensity and duration. Lymphocyte proliferation was inhibited after 2 h of noradrenaline infusion, and both catecholamines promoted monocyte and neutrophil phagocytosis. These findings indicate a shift from adaptive to innate immunity in stressful situations. This study is the first (to our knowledge) to systematically investigate specific glucocorticoid and catecholamine actions on the porcine immune system in this level of detail and confirms many similarities to humans, thus strengthening the pig as a human model in psychoneuroimmunology.