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Gene expression analysis of toll-like receptor pathways in heterophils from genetic chicken lines that differ in their susceptibility to Salmonella enteritidis

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Previously conducted studies using two chicken lines (A and B) show that line A birds have increased resistance to a number of bacterial and protozoan challenges and that heterophils isolated from line A birds are functionally more responsive. Furthermore, when stimulated with toll-like receptor (TLR) agonists, heterophils from line A expressed a totally different cytokine and chemokine mRNA expression pattern than heterophils from line B. A large-scale gene expression profile using an Agilent 44K microarray on heterophils isolated from line A and line B also revealed significantly differential expression in many immune-related genes following Salmonella enteritidis (SE) stimulation, which included genes involved in the TLR pathway. Therefore, we hypothesize the differences between the lines result from distinctive TLR pathway signaling cascades that mediate heterophil function and thus innate immune responsiveness to SE. Using quantitative RT-PCR on mRNA from heterophils isolated from control and SE-stimulated heterophils of each line, we profiled the expression of all chicken homologous genes identified in a reference TLR pathway. Several differentially expressed genes found were involved in the TLR-induced My88-dependent pathway, showing higher gene expression in line A than line B heterophils following SE stimulation. These genes included the toll-like receptor genes TLR4, TLR15, TLR21, MD2, the adaptor proteins toll-interleukin 1 receptor domain containing adaptor protein (TIRAP), tumor necrosis factor-receptor associated factor 3 (TRAF3), the I'B kinases TGF-ß-activating kinase 1 (TAK1), IKKe and IKKa, the transcription factors NFkB2 and interferon regulatory factor 7 (IRF7), phosphoinositol-3 kinase (PI-3K), and the mitogen-activated protein kinase (MAPK) p38. These results indicate that higher expression of TLR signaling activation of both MyD88-dependent and TRIF-dependent pathways are more beneficial to avian heterophil-mediated innate immunity, and a complicated regulation of down-stream adaptors is involved in stronger induction of a TLR-mediated innate response in the resistant line A. These findings identify new targets for genetic selection of chickens to increase resistance to bacterial infections.
Michael H. Kogut , Hsin-I Chiang , Christina L. Swaggerty , Igal Y. Pevzner , Huaijun Zhou
Protozoa , Salmonella enteritidis , agonists , artificial selection , bacterial infections , biochemical pathways , chemokines , chickens , disease resistance , gene expression , gene expression regulation , genes , genetic lines , heterophils , immune response , interferons , interleukin-1 , messenger RNA , microarray technology , mitogen-activated protein kinase , phosphatidylinositol 3-kinase , proteins , receptors , reverse transcriptase polymerase chain reaction , sequence homology , signal transduction , transcription (genetics) , transcription factors , transforming growth factor beta , tumor necrosis factors
Frontiers in genetics 2012 7 4 v.3 no.121
Journal Articles, USDA Authors, Peer-Reviewed
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