title: Th17-skewed immune response and cluster of differentiation 40 ligand expression in canine steroid-responsive meningitis-arteritis, a large animal model for neutrophilic meningitis.
abstract: Steroid-responsive meningitis-arteritis (SRMA) is an immune-mediated disorder characterized by neutrophilic pleocytosis and an arteritis particularly in the cervical leptomeninges. Previous studies of the disease have shown increased levels of IL-6 and TGF-ß1in cerebrospinal fluid (CSF). In the presence of these cytokines, naive CD4+ cells differentiate into Th17 lymphocytes which synthesize interleukin 17 (IL-17). It has been shown that IL-17 plays an active role in autoimmune diseases, it induces and mediates inflammatory responses and has an important role in recruitment of neutrophils. The hypothesis of a Th17-skewed immune response in SRMA should be supported by evaluating IL-17 and CD40L, inducing the vasculitis.
  
  
  
  An enzyme-linked immunosorbent assay (ELISA) was performed to measure IL-17 and CD40L in serum and CSF from a total of 79 dogs. Measurements of patients suffering from SRMA in the acute state (SRMA A) were compared with levels of patients under treatment with steroids (SRMA T), recurrence of the disease (SRMA R), other neurological disorders, and healthy dogs, using the two-part test. Additionally, secretion of IL-17 and interferon gamma (IFN-γ) from the peripheral blood mononuclear cells (PBMCs) was confirmed by an enzyme-linked immunospot (ELISpot) assay.
  
  
  
  Significant higher levels of IL-17 were found in CSF of dogs with SRMA A compared with SRMA T, other neurological disorders and healthy dogs (p < 0.0001). In addition, levels of CD40L in CSF in dogs with SRMA A and SRMA R were significantly higher than in those with SRMA T (p = 0.0004) and healthy controls (p = 0.014). Furthermore, CSF concentrations of IL-17 and CD40L showed a strong positive correlation among each other (rSpear = 0.6601; p < 0.0001) and with the degree of pleocytosis (rSpear = 0.8842; p < 0.0001 and rSpear = 0.6649; p < 0.0001, respectively). IL-17 synthesis from PBMCs in SRMA patients was confirmed; however, IL-17 is mainly intrathecally produced.
  
  
  
  These results imply that Th17 cells are inducing the autoimmune response in SRMA and are involved in the severe neutrophilic pleocytosis and disruption of the blood-brain barrier (BBB). CD-40L intrathecal synthesis might be involved in the striking vasculitis. The investigation of the role of IL-17 in SRMA might elucidate important pathomechanism and open new therapeutic strategies.
authors.affiliation: Department of Small Animal Medicine and Surgery, University of Veterinary Medicine, Bünteweg 9, 30559, Hannover, Germany. jessica.freundt.revilla@tiho-hannover.de.|Center for Systems Neuroscience, Hannover, Germany. jessica.freundt.revilla@tiho-hannover.de.
authors.forename: Jessica
authors.initials: J
authors.lastname: Freundt-Revilla
authors.affiliation: Department of Small Animal Medicine and Surgery, University of Veterinary Medicine, Bünteweg 9, 30559, Hannover, Germany.
authors.forename: Arianna
authors.initials: A
authors.lastname: Maiolini
authors.affiliation: Department of Small Animal Medicine and Surgery, University of Veterinary Medicine, Bünteweg 9, 30559, Hannover, Germany.
authors.forename: Regina
authors.initials: R
authors.lastname: Carlson
authors.affiliation: Institute for Biometry, Epidemiology and Information Processing, University of Veterinary Medicine, Hannover, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Beyerbach
authors.affiliation: Tierärztliche Praxis für Neurologie, Dettelbach, Germany.
authors.forename: Kai
authors.initials: K
authors.lastname: Rentmeister
authors.affiliation: Department of Small Animal Medicine, University of Leipzig, Leipzig, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Flegel
authors.affiliation: Clinic of Small Animal Medicine, Centre for Clinical Veterinary Medicine, LMU Munich, Munich, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Fischer
authors.affiliation: Department of Small Animal Medicine and Surgery, University of Veterinary Medicine, Bünteweg 9, 30559, Hannover, Germany.|Center for Systems Neuroscience, Hannover, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Tipold
mesh_terms: D000818:Animals; D001167:Arteritis / Q000134:cerebrospinal fluid / Q000188:drug therapy*; D023201:CD40 Ligand / Q000097:blood / Q000134:cerebrospinal fluid; D004195:Disease Models, Animal; D004285:Dogs; D004797:Enzyme-Linked Immunosorbent Assay; D005786:Gene Expression Regulation / Q000187:drug effects*; D007371:Interferon-gamma / Q000378:metabolism; D020381:Interleukin-17 / Q000097:blood / Q000134:cerebrospinal fluid / Q000378:metabolism; D007963:Leukocytes, Mononuclear / Q000378:metabolism; D008581:Meningitis / Q000134:cerebrospinal fluid / Q000188:drug therapy*; D012189:Retrospective Studies; D013256:Steroids / Q000494:pharmacology* / Q000627:therapeutic use*
chemical_list: C508717:IL17A protein, human; D020381:Interleukin-17; D013256:Steroids; D023201:CD40 Ligand; D007371:Interferon-gamma
keywords: Canine; Cerebrospinal fluid (CSF); Cluster of differentiation 40 ligand (CD40L); Interferon gamma (IFN-γ); Interleukin-17 (IL-17); Serum; Steroid-responsive meningitis-arteritis (SRMA)