title: Increased complement consumption in MuSK-antibody-positive myasthenia gravis patients.
abstract: OBJECTIVE
  To investigate the activation of different complement pathways in myasthenia gravis (MG) subtypes.
  
  
  METHODS
  Levels of complement breakdown products for different complement pathways were measured using ELISA in sera of acetylcholine receptor antibody (AChR-Ab)-positive (n = 21), muscle-specific receptor tyrosine kinase (MuSK)-Ab-positive (n = 23) and seronegative generalized MG patients (n = 21) and healthy controls (n = 22). Levels of factor Bb (FBb), the breakdown product of factor B, and C4d, the breakdown product of C4, were measured to evaluate the activity of the alternative and classical complement pathways, respectively. Serum iC3b levels were analyzed to assess total complement activity. The results were expressed as OD values.
  
  
  RESULTS
  MuSK-Ab-positive MG patients had a significantly higher mean concentration of serum FBb (0.638) than other MG subtypes (0.446 for AChR-Ab-positive, 0.537 for seronegative MG patients) and healthy controls (0.434) (p = 0.045). Mean serum iC3b (1.549-1.780) and C4d (0.364-0.395) levels were comparable among the groups.
  
  
  CONCLUSIONS
  Our results suggest that MuSK-Ab-positive MG patients might have a complement-activating serum factor and the alternative complement pathway might be involved in the pathogenesis of the disease.
authors: Department of Neurology, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey. drerdem@yahoo.com
authors: Erdem
authors: E
authors: Tüzün
authors: Vuslat
authors: V
authors: Yılmaz
authors: Yeşim
authors: Y
authors: Parman
authors: Piraye
authors: P
authors: Oflazer
authors: Feza
authors: F
authors: Deymeer
authors: Güher
authors: G
authors: Saruhan-Direskeneli
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D000937:Antigen-Antibody Reactions; D001323:Autoantibodies / Q000096:biosynthesis / Q000276:immunology / Q000378:metabolism; D016022:Case-Control Studies; D002648:Child; D003167:Complement Activation; D003179:Complement C3b / Q000096:biosynthesis / Q000276:immunology / Q000378:metabolism; D015934:Complement C4a / Q000276:immunology / Q000378:metabolism; D011415:Complement Factor B / Q000096:biosynthesis / Q000378:metabolism; D003165:Complement System Proteins / Q000096:biosynthesis* / Q000276:immunology / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000276:immunology / Q000378:metabolism; D009157:Myasthenia Gravis / Q000276:immunology / Q000473:pathology*; D020794:Receptor Protein-Tyrosine Kinases; D011950:Receptors, Cholinergic; D055815:Young Adult
chemical_list: D001323:Autoantibodies; D011950:Receptors, Cholinergic; D003179:Complement C3b; D015934:Complement C4a; D003165:Complement System Proteins; D020794:Receptor Protein-Tyrosine Kinases; D011415:Complement Factor B