Tissue-specific mRNA expression profiles of porcine Toll-like receptors at different ages in germ-free and conventional pigs

Abstract

Toll-like receptors (TLRs), key initiators of innate immune responses, recognize antigens and are essential in linking innate and adaptive immune responses. Misrecognition and over-stimulation/expression of TLRs may contribute to the development of chronic inflammatory diseases and autoimmune diseases. However, appropriate and mature TLR responses are associated with the establishment of resistance against some infectious diseases. In this study, we assessed the mRNA expression profile of TLRs 1-10 in splenic and ileal mononuclear cells (MNCs) and dendritic cells (DCs) of germ-free (GF) and conventional pigs at different ages. We found that the TLR mRNA expression profiles were distinct between GF and conventional pigs. The expression profiles were also significantly different between splenic and ileal MNCs/DCs. Comparison of the TLR expression profiles in GF and conventional newborn and young pigs demonstrated that exposure to commensal microbiota may play a more important role than age in TLR mRNA expression profiles. To our knowledge, this is the first report that systematically assesses porcine TLRs 1-10 mRNA expression profiles in MNCs and DCs from GF and conventional pigs at different ages. These results further highlighted that the commensal microbiota of neonates play a critical role through TLR signaling in the development of systemic and mucosal immune systems.

The intestinal microbiota contributes to the growth and physiological state of muscle tissue in piglets

“…GF pigs are an experimental sterile large animal model with a natural advantage: the absence of gut microflora 19 , 20 . In previous studies, GF pigs were used to reveal the influence of microbiota on the formation and maturation of the immune system mainly 21 , 22 . The principal aim of this study was to reveal the direct causal effects of intestinal microbiota colonization on pig muscle tissue.…”

A window of opportunity : Modulation of the porcine gut microbiota and immune system by feed additives in early life

“…Supplementation of EcN in early life aims at providing the gut with advantageous commensal bacteria that directly or indirectly (by affecting gut barrier function) influence the immune responsiveness. Several studies indicated that EcN activates Toll-like Receptor 4 (TLR-4) that recognizes the lipid A component of semi-rough type LPS present in the outer cell membrane of EcN [117,233,247], and has been identified along the porcine GIT and on porcine blood and lymphoid DCs [71,248,249]. However, we neither observed any effects on the gut epithelial barrier, nor did we detect changes with regards to DC numbers or DC maturation (upregulation of CD80/86).…”

Effects of Escherichia coli Nissle 1917 on the Porcine Gut Microbiota, Intestinal Epithelium and Immune System in Early Life

“…Considering the decrease of Proteobacteria diversity, EcN may have hindered pathogenic enterobacteria, thereby influencing the immune response. As for direct effects, several studies indicated that EcN activates Toll-like Receptor 4 (TLR-4) that recognizes the lipid A component of semi-rough type LPS present in the outer cell membrane of EcN (Grozdanov et al, 2002;Grabig et al, 2006;Adam et al, 2010), and has been identified along the porcine GIT and on porcine blood and lymphoid DCs (Gourbeyre et al, 2015;Auray et al, 2016;Shao et al, 2016). Conversely, TLR-4 expression in the ileum, colon or MLN of 1-week-old gnotobiotic piglets was not altered by EcN (Splichal et al, 2019).…”