title: Flow cytometric analysis of phospho-p38 mitogen-activated kinase (MAPK): p38 MAPK does not mediate the effect of adalimumab on peripheral T cell cytokine production in rheumatoid arthritis.
abstract: BACKGROUND
  The therapeutic effect of TNFalpha inhibition in rheumatoid arthritis (RA) is accompanied by an altered peripheral T cell cytokine profile, but the underlying mechanisms are not well known. In CD4+ T cells, TNF signalling includes the p38 MAP kinase (MAPK) pathway, which is also involved in proliferation and production of IL-4 and IFNgamma.
  
  
  METHODS
  Phosphorylation of p38 MAPK was analysed flow cytometrically in peripheral blood mononuclear cells (PBMC) from healthy individuals and RA patients before and after adalimumab therapy. Cytokine production by CD3/CD28-stimulated PBMC was measured in the supernatant.
  
  
  RESULTS
  Despite a transient activation of p38 MAPK in response to cellular stress from the cell separation, a significant decrease of spontaneous p38 MAPK phosphorylation was observed after adalimumab, compared to RA patients with active disease. Brief stimulation with TNFalpha/IL-1beta significantly activated p38 MAPK after but not before adalimumab therapy. In CD3/CD28-stimulated PBMC, significantly less p38 MAPK activation and increased IFNgamma production were observed after adalimumab therapy.
  
  
  CONCLUSIONS
  In rheumatoid arthritis, adalimumab therapy decreases the phosphorylation of p38 MAPK except for its response to TNF/IL-1, while enhancing the production of IFNgamma. This suggests that p38 MAPK is not directly involved in the effect of TNF inhibition on cytokine production.
authors.affiliation: Faculty of Medicine, Departments of Immunology-Allergology-Rheumatology, University of Antwerp, Universiteitsplein 1, 2610 Antwerp, Belgium. nicolaas.aerts@ua.ac.be
authors.forename: Nicolaas E
authors.initials: NE
authors.lastname: Aerts
authors.forename: Didier G
authors.initials: DG
authors.lastname: Ebo
authors.forename: Chris H
authors.initials: CH
authors.lastname: Bridts
authors.forename: Wim J
authors.initials: WJ
authors.lastname: Stevens
authors.forename: Luc S
authors.initials: LS
authors.lastname: De Clerck
mesh_terms: D000068879:Adalimumab; D000328:Adult; D000368:Aged; D000911:Antibodies, Monoclonal / Q000494:pharmacology* / Q000627:therapeutic use; D061067:Antibodies, Monoclonal, Humanized; D018501:Antirheumatic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D001172:Arthritis, Rheumatoid / Q000188:drug therapy / Q000201:enzymology / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000187:drug effects* / Q000201:enzymology / Q000276:immunology; D016207:Cytokines / Q000096:biosynthesis*; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D053583:Interleukin-1beta / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D010766:Phosphorylation; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D018501:Antirheumatic Agents; D016207:Cytokines; D053583:Interleukin-1beta; D014409:Tumor Necrosis Factor-alpha; D048051:p38 Mitogen-Activated Protein Kinases; D000068879:Adalimumab