title: Difference in B cell activation between dermatomyositis and polymyositis: analysis of the expression of RP105 on peripheral blood B cells.
abstract: BACKGROUND
  It has previously been shown that RP105, a new B cell surface protein, is lost in activated human B cells.
  
  
  OBJECTIVE
  To investigate whether there is a difference in B cell activation between patients with dermatomyositis (DM) and those with polymyositis (PM) using RP105 as a marker.
  
  
  METHODS
  The population of RP105 negative B cells (activated B cells) in the peripheral blood mononuclear cells of seven patients with dermatomyositis (DM) and 11 with polymyositis (PM) was analysed by flow cytometry.
  
  
  RESULTS
  The percentage of RP105 negative B cells in the peripheral blood of patients with PM was low (5.8 (SD 2.4)%), similar to that of normal subjects. In contrast, all patients with DM showed increased RP105 negative B cell populations (33.0 (6.9)%). Bronchoalveolar lavage fluid from a patient with DM and active interstitial pneumonitis contained a large number of RP105 negative B cells.
  
  
  CONCLUSIONS
  These findings suggest that the expansion of RP105 negative B cells is a hallmark of DM, and that B cell activation in DM may be pathogenetically different from that in PM.
authors.affiliation: Department of Internal Medicine, Saga Medical School, 5-1-1 Nabeshima, Saga 849-8501, Japan. kikuchi@post.saga-med.ac.jp
authors.forename: Y
authors.initials: Y
authors.lastname: Kikuchi
authors.forename: S
authors.initials: S
authors.lastname: Koarada
authors.forename: Y
authors.initials: Y
authors.lastname: Tada
authors.forename: O
authors.initials: O
authors.lastname: Ushiyama
authors.forename: F
authors.initials: F
authors.lastname: Morito
authors.forename: N
authors.initials: N
authors.lastname: Suzuki
authors.forename: A
authors.initials: A
authors.lastname: Ohta
authors.forename: T
authors.initials: T
authors.lastname: Horiuchi
authors.forename: K
authors.initials: K
authors.lastname: Miyake
authors.forename: K
authors.initials: K
authors.lastname: Nagasawa
mesh_terms: D000328:Adult; D000368:Aged; D015703:Antigens, CD; D000954:Antigens, Surface / Q000097:blood*; D001402:B-Lymphocytes / Q000276:immunology*; D015415:Biomarkers / Q000097:blood; D001992:Bronchoalveolar Lavage Fluid / Q000276:immunology; D003882:Dermatomyositis / Q000276:immunology; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D017563:Lung Diseases, Interstitial / Q000276:immunology; D008213:Lymphocyte Activation; D008297:Male; D008875:Middle Aged; D017285:Polymyositis / Q000276:immunology*
chemical_list: D015703:Antigens, CD; D000954:Antigens, Surface; D015415:Biomarkers; C092722:CD180 protein, human