title: Unmasking of autoreactive CD4 T cells by depletion of CD25 regulatory T cells in systemic lupus erythematosus.
abstract: OBJECTIVE
  Autoreactive CD4 T cells specific for nuclear peptide antigens play an important role in tolerance breakdown during the course of systemic lupus erythematosus (SLE). However, reliable detection of these cells is limited due to their low frequency in peripheral blood. The authors assess autoreactive CD4 T cells in a representative SLE collective (n=38) by flow cytometry and study the influence of regulatory T cells (Treg) on their antigenic challenge.
  
  
  METHODS
  CD4 T-cell responses were determined according to intracellular CD154 expression induced after 6-h short-term in-vitro stimulation with the SLE-associated autoantigen SmD1(83-119). To clarify the influence of Treg on the activation of autoreactive CD4 T cells, CD25 Treg were depleted by magnetic activated cell sorting before antigen-specific stimulation in selected experiments.
  
  
  RESULTS
  In the presence of Treg, autoreactive CD4 T-cell responses to SmD1(83-119) were hardly observable. However, Treg removal significantly increased the frequency of detectable SmD1(83-119)-specific CD4 T cells in SLE patients but not in healthy individuals. Consequently, by depleting Treg the percentage of SmD1(83-119)-reactive SLE patients increased from 18.2% to 63.6%. This unmasked autoreactivity of CD4 T cells correlated with the disease activity as determined by the SLE disease activity index (p=0.005*, r=0.779).
  
  
  CONCLUSIONS
  These data highlight the pivotal role of the balance between autoreactive CD4 T cells and CD25 Treg in the dynamic course of human SLE. Analysing CD154 expression in combination with a depletion of CD25 Treg, as shown here, may be of further use in approaching autoantigen-specific CD4 T cells in SLE and other autoimmune diseases.
authors.affiliation: Department of Rheumatology and Clinical Immunology, University Hospital Charité, Berlin, Germany.
authors.forename: Jan Broder
authors.initials: JB
authors.lastname: Engler
authors.forename: Reinmar
authors.initials: R
authors.lastname: Undeutsch
authors.forename: Lutz
authors.initials: L
authors.lastname: Kloke
authors.forename: Stefan
authors.initials: S
authors.lastname: Rosenberger
authors.forename: Marina
authors.initials: M
authors.lastname: Backhaus
authors.forename: Udo
authors.initials: U
authors.lastname: Schneider
authors.forename: Karl
authors.initials: K
authors.lastname: Egerer
authors.forename: Duska
authors.initials: D
authors.lastname: Dragun
authors.forename: Jörg
authors.initials: J
authors.lastname: Hofmann
authors.forename: Dörte
authors.initials: D
authors.lastname: Huscher
authors.forename: Gerd-Rüdiger
authors.initials: GR
authors.lastname: Burmester
authors.forename: Jens Y
authors.initials: JY
authors.lastname: Humrich
authors.forename: Philipp
authors.initials: P
authors.lastname: Enghard
authors.forename: Gabriela
authors.initials: G
authors.lastname: Riemekasten
mesh_terms: D000328:Adult; D000368:Aged; D001324:Autoantigens / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D023201:CD40 Ligand / Q000097:blood; D002478:Cells, Cultured; D018984:Epitopes, T-Lymphocyte / Q000276:immunology; D005260:Female; D006801:Humans; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D053645:Interleukin-2 Receptor alpha Subunit / Q000097:blood*; D008180:Lupus Erythematosus, Systemic / Q000188:drug therapy / Q000276:immunology*; D008213:Lymphocyte Activation / Q000276:immunology; D008297:Male; D008875:Middle Aged; D050378:T-Lymphocytes, Regulatory / Q000276:immunology; D055815:Young Adult; D055517:snRNP Core Proteins / Q000276:immunology
chemical_list: D001324:Autoantigens; D018984:Epitopes, T-Lymphocyte; C508017:IL2RA protein, human; D007166:Immunosuppressive Agents; D053645:Interleukin-2 Receptor alpha Subunit; C526409:SNRPD1 protein, human; D055517:snRNP Core Proteins; D023201:CD40 Ligand