title: Characteristics of NK cell activity in patients with systemic sclerosis.
abstract: BACKGROUND
  Previous studies have shown an increased expression of natural killer (NK) cells in the peripheral blood of patients with systemic sclerosis (SSc). NK cells are part of innate immunity, recognizing infected cells through killer immunoglobulin-like receptors (KIR), which show marked polymorphism. A novel model has been proposed predicting the activity of NK cells, evaluating whether there is excessive activation (EA), excessive inhibition (EI) or balance (B) (neutral).
  
  
  OBJECTIVE
  To evaluate the activity of NK cells in patients with SSc and compare it with that of a control group.
  
  
  METHODS
  This study comprised 110 patients with SSc and 115 healthy controls. A novel model that predicts the activity of NK cells was used. For that, cells with their respective KIR/HLA-C and Bw4 ligands were considered. The activity of NK cells was defined as EA, EI, or B.
  
  
  RESULTS
  Our results showed that 63.5% of healthy controls had the KIR phenotype characterized by EI, as compared with 39.1% of the patients with SSc (P = 0.001). Considering only KIR2DL2-positive individuals, 34.7% of EI was found in healthy controls and 10.9% in patients with SSc (P < 0.001).
  
  
  CONCLUSIONS
  In our study, the model that predicts the action of NK cells showed that healthy controls have higher frequency of EI as compared with SSc patients, suggesting a protective effect of the EI profile against the development of SSc. These results suggest a potential role of NK cells in the pathogenesis of SSc, but further studies should be conducted to confirm our data.
authors.affiliation: Serviço de Reumatologia and Serviço de Imunologia, Hospital de Clínicas de Porto Alegre, Medical School, Universidade Federal do Rio Grande do Sul –HCPA-UFRGS, Brazil.
authors.forename: Patricia Hartstein
authors.initials: PH
authors.lastname: Salim
authors.forename: Mariana
authors.initials: M
authors.lastname: Jobim
authors.forename: Markus
authors.initials: M
authors.lastname: Bredemeier
authors.forename: José Artur Bogo
authors.initials: JA
authors.lastname: Chies
authors.forename: João Carlos Tavares
authors.initials: JC
authors.lastname: Brenol
authors.forename: Luiz Fernando
authors.initials: LF
authors.lastname: Jobim
authors.forename: Ricardo Machado
authors.initials: RM
authors.lastname: Xavier
mesh_terms: D006801:Humans; D007694:Killer Cells, Natural / Q000276:immunology*; D012595:Scleroderma, Systemic / Q000276:immunology*