title: Secreted semaphorin 5A activates immune effector cells and is a biomarker for rheumatoid arthritis.
abstract: OBJECTIVE
  To investigate the role of the multifunctional protein semaphorin 5A (Sema5A) in modulating cellular immune responses and as a biomarker in rheumatoid arthritis (RA).
  
  
  METHODS
  A soluble form of recombinant Sema5A was used to assess its effect on the functions of primary T cells and natural killer (NK) cells isolated from the peripheral blood of healthy donors. Cell proliferation and expression of transcription factors were determined by flow cytometry. Cytokine secretion was analyzed using Luminex technology. Serum samples obtained from 145 patients with RA and control serum samples obtained from healthy individuals or patients with non-RA rheumatic diseases were analyzed for the presence of secreted Sema5A, using enzyme-linked immunosorbent assays and immunoblotting.
  
  
  RESULTS
  Soluble Sema5A strongly increased T cell and NK cell proliferation and induced the secretion of proinflammatory Th1/Th17 cytokines. Accordingly, Sema5A stimulation caused significant up-regulation of T-bet and retinoic acid receptor-related orphan nuclear receptor γt levels in T cells. In addition, significantly elevated levels of secreted Sema5A were detected in the serum of patients with RA compared with control serum. Sema5A levels were highest in patients with RA who were positive for the RA biomarker anti-cyclic citrullinated peptide (P < 0.001 versus patients with systemic lupus erythematosus and patients with Sjögren's syndrome) and correlated with the levels of rheumatoid factor.
  
  
  CONCLUSIONS
  Soluble Sema5A is a potent activator of T cells and NK cells in vitro, and high serum levels of Sema5A are associated with RA. Taken together, the results indicate that Sema5A contributes to the pathogenesis of RA through antigen-independent T cell and NK cell activation. Hence, Sema5A is a promising complementary biomarker for the diagnosis of RA.
authors.affiliation: Hannover Medical School, Hannover, Germany.
authors.forename: Christiane
authors.initials: C
authors.lastname: Gras
authors.forename: Britta
authors.initials: B
authors.lastname: Eiz-Vesper
authors.forename: Yarua
authors.initials: Y
authors.lastname: Jaimes
authors.forename: Stephan
authors.initials: S
authors.lastname: Immenschuh
authors.forename: Roland
authors.initials: R
authors.lastname: Jacobs
authors.forename: Torsten
authors.initials: T
authors.lastname: Witte
authors.forename: Rainer
authors.initials: R
authors.lastname: Blasczyk
authors.forename: Constança
authors.initials: C
authors.lastname: Figueiredo
mesh_terms: D001172:Arthritis, Rheumatoid / Q000378:metabolism* / Q000473:pathology; D015415:Biomarkers / Q000378:metabolism; D002097:C-Reactive Protein / Q000378:metabolism; D016022:Case-Control Studies; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism; D006801:Humans; D007694:Killer Cells, Natural / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D008180:Lupus Erythematosus, Systemic / Q000378:metabolism / Q000473:pathology; D008565:Membrane Proteins / Q000378:metabolism* / Q000494:pharmacology*; D009419:Nerve Tissue Proteins / Q000378:metabolism* / Q000494:pharmacology*; D012217:Rheumatoid Factor / Q000378:metabolism; D039961:Semaphorins; D012859:Sjogren's Syndrome / Q000378:metabolism / Q000473:pathology; D013601:T-Lymphocytes / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology
chemical_list: D015415:Biomarkers; D016207:Cytokines; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; C491228:SEMA5A protein, human; D039961:Semaphorins; D002097:C-Reactive Protein; D012217:Rheumatoid Factor