title: CTLA-4 (CD152) blockade does not cause a pro-inflammatory cytokine profile in regulatory T cells.
abstract: OBJECTIVE
  The activation of T cells is closely regulated. One cell intrinsic mechanism is based on the expression of inhibitory molecules; another is mediated by regulatory T (Treg) cells. The co-regulatory molecule CTLA-4 is constitutively expressed by Treg cells and up-regulated in effector-T-cells after activation. Recently, it was described that Treg cells can display an unstable phenotype and convert into pathogenic pro-inflammatory cytokine secreting cells. Here we have analysed the role of CTLA-4 in the regulation of cytokine production by T-helper (Th) cells with a special focus on Treg cells.
  
  
  METHODS
  Proliferation of unstimulated CTLA-4 knock-out and wild-type cells as well as their activation status and the impact of CTLA-4 blockade on proliferation of Treg and effector T cells under stimulation were analysed by flow cytometry. Furthermore, the cytokine concentrations were analysed by a multiplex suspension assay.
  
  
  RESULTS
  CTLA-4 knock-out T cells proliferated without stimulation and displayed an activated phenotype ex vivo. Proliferation of effector but also that of Treg cells was controlled by CTLA-4. The blockade of CTLA-4 led to an increased secretion of GM-CSF, IL-1β, IL-2, and IFN-γ by Th cells. However, the blockade of CTLA-4 in Treg cells did not cause any conversion into pathogenic pro-inflammatory T cells, since the non-cytokine secreting phenotype remained unchanged.
  
  
  CONCLUSIONS
  These results have major implications on therapies targeting the CTLA-4-system, e.g. by CTLA4-Ig or anti-CTLA-4-antibodies, as the blockade of CTLA-4 did not unlock the stability of Treg cells.
authors.affiliation: Department of Rheumatology and Clinical Immunology, Charité - University Hospital, 10117 Berlin, Germany. paula.kolar@charite.de
authors.forename: P
authors.initials: P
authors.lastname: Kolar
authors.forename: H
authors.initials: H
authors.lastname: Hoff
authors.forename: P
authors.initials: P
authors.lastname: Maschmeyer
authors.forename: G-R
authors.initials: GR
authors.lastname: Burmester
authors.forename: M C
authors.initials: MC
authors.lastname: Brunner-Weinzierl
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000235:genetics* / Q000276:immunology*; D001327:Autoimmune Diseases / Q000276:immunology* / Q000628:therapy; D060908:CTLA-4 Antigen; D002455:Cell Division / Q000276:immunology; D002478:Cells, Cultured; D016207:Cytokines / Q000276:immunology; D016130:Immunophenotyping; D008221:Lymphoid Tissue / Q000276:immunology; D008232:Lymphoproliferative Disorders / Q000276:immunology* / Q000628:therapy; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D050378:T-Lymphocytes, Regulatory / Q000166:cytology / Q000276:immunology*
chemical_list: D015703:Antigens, CD; D060908:CTLA-4 Antigen; C556707:Ctla4 protein, mouse; D016207:Cytokines