Pattern recognition receptors are differentially expressed in the pig small intestine

Abstract

International audiencePattern Recognition Receptors (PRR) include Toll-like receptors and NOD-like receptors. These molecules are involved in the innate immune response to infection, triggering inflammatory responses. The aim of this study was to determine if PRR and inflammatory cytokines are differentially expressed along the intestinal segments and relative lymphoid organs of healthy pigs. Duodenum, jejunum, ileum, jejunal Peyer patches, ileal Peyer patches and mesenteric lymph nodes were collected from 32 healthy pigs to study the expression of genes encoding for PRR (Tolllike receptors 1 to 10, NOD1 and NOD2) and inflammatory cytokines by quantitative PCR. Toll-like receptors 1, 2, 4, 5, 6, 8, 9, 10 were less expressed in the duodenum than in the other intestinal segments. Toll-like receptors 1, 2, 4, 7, 8, 9, 10, NOD1, 2 were more expressed in the mesenteric lymph nodes than in the intestinal segments. Toll-like receptors 1, 7, 8, 9, 10 showed a more pronounced expression in Peyer patches than in relative intestinal segment. A heatmap analysis of our data highlights two distinct clusters of organs. Intestinal segments belong to the first cluster. They displayed high expression levels of TLR 5, 6 and IL-1 beta. Among these segments, duodenum was characterized by a weak expression of PRRs and cytokines, which may be related to its local lumen environment, poor in microorganisms. Lymphoid organs belong to the second cluster. They showed weak expression levels of TLR3, 5 and IL-1 beta and a high expression of TLR 1, 2, 7, 9, 10, IL-6 and TNF-alpha. Among these organs, mesenteric lymph nodes presented a high expression of most PRR and inflammatory cytokines, which may be related to their antigen uptake function. Our findings demonstrate thus that PRR and cytokines are differentially expressed along the intestine, highlighting segment-specific mechanisms. Acknowledgment: The present study was supported by the ANR “Sus Flora” research grant (coordinator: Claire Rogel-Gaillard)