Stress, Nutrition, and Intestinal Immune Responses in Pigs — A Review

Lee, In Kyu; Kye, Yoon Chul; Kim, Girak; Kim, Han Wool; Gu, Min Jeong; Umboh, Johnny; Maaruf, Kartini; Kim, Sung Woo; Yun, Cheol-Heui

Status of porcine intestinal immune system is immature at birth, which develops further during perinatal period and then reaches to adult values between 5 and 7 weeks of life. Gut epithelial cells communicate with intestinal innate immune system, forming a functional barrier to antigens from diet and pathogens. Toll-like receptors (TLRs) are emerging as a functionally important class of membrane and cytosolic receptors with key roles in recognition of pathogens for innate immune modulation. Induction of adaptive immune responses begins with processing and presentation of antigen by specialized antigen presenting cells , in the organized tissues of the Peyer's patches or mesenteric lymph nodes in the intestine (Gebert et al., 1996) . One of the most important parts of adaptive intestinal immunity would be IgA responses, which require interactions between T and B lymphocytes (Cheon et al., 2014) within gut-associated lymphoid tissues. Livestock are exposed to various stressors including diet, temperature, weaning and infection. Abrupt changes of these stress factors influence animal health negatively, resulting in lower productivity. Such stressors often challenge homeostasis of animals by inducing systemic or local inflammatory responses coincident with neuroendocrine alteration. Considering the fact that gastrointestinal tract is tightly controlled by a reciprocal circuit composed of the immune system and neuro-endocrine system (Kayama and Takeda, 2012; Hayes et al., 2014) , reducing stress would significantly improve gut homeostatic balance of livestock.