title: Serum complement activation in central nervous system disease in Sjögren's syndrome.
abstract: OBJECTIVE
  Central nervous system disease and vasculitis are extraglandular manifestations of Sjögren's syndrome. In our experience, central nervous system disease develops in approximately 70 percent of patients with Sjögren's syndrome and biopsy documented peripheral vasculitis. In order to further investigate the pathogenesis of central nervous system disease and its relationship to peripheral vasculitis in Sjögren's syndrome, we examined sera of patients with Sjögren's syndrome with and without focal central nervous system involvement for evidence of terminal complement pathway activation.
  
  
  METHODS
  Patients were classified as having active focal central nervous system involvement only when they had focal neurologic deficits on physical examination, plus at least one abnormal neurodiagnostic test result. Two thirds of these patients also had cognitive or psychiatric dysfunction. Patients were classified as having peripheral vasculitis if they had clinical and histopathologic documentation of vascular inflammation. Serum SC5b-9 was measured by a sensitive enzyme-linked immunoabsorbent assay. Total hemolytic complement assay, measurement of serum C3 and C4 by radial immunodiffusion, and determination of immune complexes were performed.
  
  
  RESULTS
  Fluid-phase terminal complement complexes (SC5b-9) were detected in the sera of 25 of 30 (83 percent) patients with focal central nervous system involvement, but in only seven of 21 (33 percent) patients with Sjögren's syndrome without focal central nervous system disease (p = 0.00084 by Yates' chi-square analysis). Four of these seven patients without focal central nervous system disease, but who had serum SC5b-9, had psychiatric or cognitive dysfunction. SC5b-9 was also detected in sera from 14 of 15 (93 percent) patients with active biopsy-documented peripheral vasculitis in contrast to 18 of 36 (50 percent) patients without clinical evidence of peripheral vasculitis (p = 0.0094). Serum SC5b-9 was a more sensitive indicator of complement activation than circulating immune complex or complement assays.
  
  
  CONCLUSIONS
  These findings suggest that terminal complement activation may participate in the pathophysiology of both central nervous system and peripheral vasculitis in Sjögren's syndrome. Serum SC5b-9 appears to be a useful diagnostic indicator of vascular inflammation in Sjögren's syndrome and appears to identify those patients at risk for central nervous system complications.
authors.affiliation: Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21239.
authors.forename: E L
authors.initials: EL
authors.lastname: Alexander
authors.forename: T T
authors.initials: TT
authors.lastname: Provost
authors.forename: M E
authors.initials: ME
authors.lastname: Sanders
authors.forename: M M
authors.initials: MM
authors.lastname: Frank
authors.forename: K A
authors.initials: KA
authors.lastname: Joiner
mesh_terms: D000936:Antigen-Antibody Complex / Q000032:analysis; D002493:Central Nervous System Diseases / Q000150:complications / Q000276:immunology*; D003167:Complement Activation; D015938:Complement Membrane Attack Complex; D003165:Complement System Proteins / Q000032:analysis*; D006023:Glycoproteins / Q000032:analysis*; D006801:Humans; D019965:Neurocognitive Disorders / Q000209:etiology / Q000276:immunology; D012859:Sjogren's Syndrome / Q000150:complications* / Q000276:immunology; D014657:Vasculitis / Q000150:complications / Q000276:immunology
chemical_list: D000936:Antigen-Antibody Complex; D015938:Complement Membrane Attack Complex; D006023:Glycoproteins; C047610:SC5b-9 protein complex; D003165:Complement System Proteins