title: A meta-analysis of cytokines in Alzheimer's disease.
abstract: BACKGROUND
  Studies suggest that inflammation is involved in the neurodegenerative cascade leading to Alzheimer's disease (AD) pathology and symptoms. This study sought to quantitatively summarize the clinical cytokine data.
  
  
  METHODS
  Original English language peer-reviewed studies measuring cytokine concentrations in AD and healthy control subjects were included. Mean (± standard deviation) cytokine concentrations for AD and control subjects were extracted.
  
  
  RESULTS
  Forty studies measuring peripheral blood cytokine concentrations and 14 measuring cerebrospinal fluid (CSF) cytokine concentrations were included. In peripheral blood, there were significantly higher concentrations (weighted mean difference [95% confidence interval]) of interleukin (IL)-6 (2.86 [1.68, 4.04] pg/mL, p < .00001, N[AD/control subjects] = 985/680, 14 studies), tumor necrosis factor (TNF)-α (3.25 [.76, 5.74] pg/mL, p = .01, N = 680/447, 14 studies), IL-1β (.55 [.32, .78] pg/mL, p < .00001, N = 574/370, 10 studies), transforming growth factor (TGF)-β (67.23 [28.62, 105.83] pg/mL, p = .0006, N = 190/158, 5 studies), IL-12 (7.60 [5.58, 9.62] pg/mL, p < .00001, N = 148/106, 5 studies), and IL-18 (15.82 [1.98, 29.66] pg/mL, p = .03, N = 131/94, 4 studies) but not of IL-4, IL-8, IL-10, interferon-γ, or C-reactive protein in AD subjects compared with control subjects. There were significantly higher concentrations of TGF-β (7.81 [2.27, 13.35] pg/mL, p =.006, N = 113/114, 5 studies) but not IL-6, TNF-α, and IL-1β in the CSF of AD subjects compared with control subjects.
  
  
  CONCLUSIONS
  These results strengthen the clinical evidence that AD is accompanied by an inflammatory response, particularly higher peripheral concentrations of IL-6, TNF-α, IL-1β, TGF-β, IL-12 and IL-18 and higher CSF concentrations of TGF-β.
authors.affiliation: Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Walter
authors.initials: W
authors.lastname: Swardfager
authors.forename: Krista
authors.initials: K
authors.lastname: Lanctôt
authors.forename: Lana
authors.initials: L
authors.lastname: Rothenburg
authors.forename: Amy
authors.initials: A
authors.lastname: Wong
authors.forename: Jaclyn
authors.initials: J
authors.lastname: Cappell
authors.forename: Nathan
authors.initials: N
authors.lastname: Herrmann
mesh_terms: D000544:Alzheimer Disease / Q000097:blood* / Q000134:cerebrospinal fluid*; D015415:Biomarkers / Q000097:blood / Q000134:cerebrospinal fluid; D016207:Cytokines / Q000097:blood* / Q000134:cerebrospinal fluid*; D006801:Humans; D018836:Inflammation Mediators / Q000097:blood / Q000134:cerebrospinal fluid
chemical_list: D015415:Biomarkers; D016207:Cytokines; D018836:Inflammation Mediators