title: Innate cytokine responses in porcine macrophage populations: evidence for differential recognition of double-stranded RNA.
abstract: Pulmonary airways are vulnerable to infection because of exposure to Ag during respiration. The innate, antiviral response must be activated rapidly after pathogen recognition, and alveolar macrophages (AMphi) play a role in this response. TLR3 and protein kinase R (PKR) recognize dsRNA, a replication intermediate of RNA viruses, and initiate transcription of IFN-alphabeta. In this study, synthetic dsRNA poly(I:C) was used to investigate innate responses of porcine AMphi compared with responses of peritoneal macrophages (PMphi). Poly(I:C) triggered IFN-alphabeta in AMphi and PMphi, but levels in AMphi were higher. In contrast, mRNA levels of IFN-stimulated genes, Mx and PKR, were greater in PMphi than AMphi. Low levels of Mx and PKR transcription in AMphi were not due to deficient type I IFN receptor signaling, as exogenous IFN-alpha induced nuclear translocation of phosphorylated STAT1. To investigate the differential mechanism by which IFN-alphabeta transcription is activated in AMphi and PMphi, 2-aminopurine (2-AP) was used to block dsRNA-mediated activation of PKR. IFN-alphabeta, Mx, and PKR mRNA levels in AMphi after poly(I:C) treatment were unaffected by 2-AP; conversely, transcription of IFN-alphabeta, Mx, or PKR remained at baseline levels in PMphi. Phosphorylated PKR was detected in PMphi, but not AMphi, after poly(I:C) treatment. In addition to IFN-alphabeta gene induction, mRNA levels of TNF-alpha and RANTES were higher in AMphi than PMphi after poly(I:C) stimulation. In summary, differential dsRNA-induced cytokine expression patterns between AMphi and PMphi provide evidence that dsRNA recognition and subsequent signaling is likely mediated via TLR3 in AMphi and PKR in PMphi.
authors.affiliation: Immunobiology Graduate Program, Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA.
authors.forename: Crystal L
authors.initials: CL
authors.lastname: Loving
authors.forename: Susan L
authors.initials: SL
authors.lastname: Brockmeier
authors.forename: Wenjun
authors.initials: W
authors.lastname: Ma
authors.forename: Juergen A
authors.initials: JA
authors.lastname: Richt
authors.forename: Randy E
authors.initials: RE
authors.lastname: Sacco
mesh_terms: D000818:Animals; D016207:Cytokines / Q000235:genetics* / Q000276:immunology; D007113:Immunity, Innate / Q000276:immunology; D016676:Macrophages, Alveolar / Q000276:immunology* / Q000378:metabolism; D011070:Poly I-C; D011485:Protein Binding; D012330:RNA, Double-Stranded / Q000378:metabolism*; D053633:Receptor, Interferon alpha-beta / Q000378:metabolism; D015398:Signal Transduction; D013552:Swine; D051196:Toll-Like Receptor 3 / Q000378:metabolism; D014158:Transcription, Genetic; D019892:eIF-2 Kinase / Q000378:metabolism
chemical_list: D016207:Cytokines; D012330:RNA, Double-Stranded; D051196:Toll-Like Receptor 3; D053633:Receptor, Interferon alpha-beta; D019892:eIF-2 Kinase; D011070:Poly I-C