title: Peripheral blood natural killer cell percentages in granulomatosis with polyangiitis correlate with disease inactivity and stage.
abstract: BACKGROUND
  The role of CD3-CD56+ natural killer (NK) cells in granulomatosis with polyangiitis (GPA) is poorly understood. Recently, it has been shown that peripheral blood NK cells can kill renal microvascular endothelial cells, suggesting a pathogenic role of NK cells in this disease. So far, subset distribution, phenotype, and function of peripheral blood NK cells in relation to GPA disease activity have not been elucidated. Moreover, it is not known whether NK cells infiltrate GPA tissue lesions.
  
  
  METHODS
  Paraffin sections of GPA granulomas and controls were stained with anti-CD56 and anti-CD3 antibodies. Peripheral blood lymphocyte subsets were analyzed by flow cytometry. NK cell degranulation was analyzed using cocultures of patient PBMCs with target cells and surface expression of CD107a. Clinical data were extracted from medical records. Statistical analysis was performed in an exploratory way.
  
  
  RESULTS
  CD56+ cells were not detectable in active granulomatous GPA lesions but were found frequently in granulomas from tuberculosis and sarcoidosis patients. In GPA, the proportion of NK cells among peripheral blood lymphocytes correlated negatively with the Birmingham Vasculitis Activity Score (BVAS) (n = 28). Accordingly, NK cell percentages correlated positively with the duration of remission (n = 28) and were significantly higher in inactive GPA (BVAS = 0, n = 17) than in active GPA, healthy controls (n = 29), and inactive control diseases (n = 12). The highest NK cell percentages were found in patients with long-term remission and tapered immunosuppressive therapy. NK cell percentages >18.5% of peripheral blood lymphocytes (n = 12/28) determined GPA inactivity with a specificity of 100%. The differentiation into CD56(dim) and CD56(bright) NK cell subsets was unchanged in GPA (n = 28), irrespective of disease activity. Similar surface expression of the activating NK cell-receptors (NKp30, NKp46, and NKG2D) was determined. Like in healthy controls, GPA NK cells degranulated in the presence of NK cell receptor ligand bearing epithelial and lymphatic target cells.
  
  
  CONCLUSIONS
  NK cells were not detectable in GPA granulomas. Peripheral blood NK cell percentages positively correlate with the suppression of GPA activity and could serve as a biomarker for GPA activity. Peripheral blood NK cells in GPA patients are mature NK cells with preserved immune recognition.
authors.affiliation: Department of Hematology, Oncology and Rheumatology, Internal Medicine V, University Hospital of Heidelberg, Im Neuenheimer Feld 410, 69120, Heidelberg, Germany. wolfgang.merkt@med.uni-heidelberg.de.|Innate Immunity Group, German Cancer Research Center, Heidelberg, Germany. wolfgang.merkt@med.uni-heidelberg.de.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Merkt
authors.affiliation: Innate Immunity Group, German Cancer Research Center, Heidelberg, Germany. prisca.sturm@gmx.de.
authors.forename: Prisca
authors.initials: P
authors.lastname: Sturm
authors.affiliation: Department of Pathology, University Hospital Heidelberg, Heidelberg, Germany. felix.lasitschka@med.uni-heidelberg.de.
authors.forename: Felix
authors.initials: F
authors.lastname: Lasitschka
authors.affiliation: Department of Hematology, Oncology and Rheumatology, Internal Medicine V, University Hospital of Heidelberg, Im Neuenheimer Feld 410, 69120, Heidelberg, Germany. theresa.tretter@med.uni-heidelberg.de.
authors.forename: Theresa
authors.initials: T
authors.lastname: Tretter
authors.affiliation: Leibniz Research Center for Working Environment and Human Factors, Dortmund, Germany. watzl@ifado.de.
authors.forename: Carsten
authors.initials: C
authors.lastname: Watzl
authors.affiliation: Institute of Medical Biometry and Informatics, University of Heidelberg, Heidelberg, Germany. saure@imbi.uni-heidelberg.de.
authors.forename: Daniel
authors.initials: D
authors.lastname: Saure
authors.affiliation: Department of Hematology, Oncology and Rheumatology, Internal Medicine V, University Hospital of Heidelberg, Im Neuenheimer Feld 410, 69120, Heidelberg, Germany. michael.hundemer@med.uni-heidelberg.de.
authors.forename: Michael
authors.initials: M
authors.lastname: Hundemer
authors.affiliation: Department of Nephrology, University Hospital of Heidelberg, Heidelberg, Germany. vedat.schwenger@med.uni-heidelberg.de.
authors.forename: Vedat
authors.initials: V
authors.lastname: Schwenger
authors.affiliation: Department of Hematology, Oncology and Rheumatology, Internal Medicine V, University Hospital of Heidelberg, Im Neuenheimer Feld 410, 69120, Heidelberg, Germany. norbert.blank@med.uni-heidelberg.de.
authors.forename: Norbert
authors.initials: N
authors.lastname: Blank
authors.affiliation: Department of Hematology, Oncology and Rheumatology, Internal Medicine V, University Hospital of Heidelberg, Im Neuenheimer Feld 410, 69120, Heidelberg, Germany. hannes.lorenz@med.uni-heidelberg.de.
authors.forename: Hanns-Martin
authors.initials: HM
authors.lastname: Lorenz
authors.affiliation: Innate Immunity Group, German Cancer Research Center, Heidelberg, Germany. a.cerwenka@dkfz-heidelberg.de.
authors.forename: Adelheid
authors.initials: A
authors.lastname: Cerwenka
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002478:Cells, Cultured; D018450:Disease Progression; D005260:Female; D014890:Granulomatosis with Polyangiitis / Q000378:metabolism* / Q000473:pathology*; D006801:Humans; D007694:Killer Cells, Natural / Q000378:metabolism* / Q000473:pathology*; D007963:Leukocytes, Mononuclear / Q000378:metabolism* / Q000473:pathology*; D008297:Male; D008875:Middle Aged