Active but not inactive granulomatosis with polyangiitis is associated with decreased and phenotypically and functionally altered CD56(dim) natural killer cells.
The role of natural killer (NK) cells in granulomatosis with polyangiitis (GPA) is poorly understood. We recently reported that peripheral blood NK cell percentages correlate with the suppression of GPA activity (cohort I). The purpose of the current study was to further characterize NK cell subsets, phenotype and function in a second GPA cohort (cohort II).



Peripheral blood lymphocyte subsets were analyzed at a clinical diagnostic laboratory. Clinical data were extracted from medical records and patients were grouped according to their activity state (remission vs. active/non-remission). Separate analysis (cohort II, n = 22) and combined analysis (cohorts I and II, n = 34/57) of NK cell counts/percentages was performed. NK cell subsets and phenotypes were analyzed by multicolor flow cytometry. Cytotoxicity assays were performed using (51)Cr-labeled K562 target cells.



In cohort II, NK cell counts were lower than the lower limit of normal in active GPA, despite normal percentages due to lymphopenia. NK cell counts, but not other lymphocyte counts, were significantly higher in remission. Combined analysis of cohorts I and II confirmed decreased NK cell counts in active GPA and increased percentages in long-term remission. Follow-up measurements of six patients revealed increasing NK cell percentages during successful induction therapy. Multicolor analysis from cohort II revealed that in active GPA, the CD56(dim) subset was responsible for decreased NK cell counts, expressed more frequently CD69, downregulated the Fc-receptor CD16 and upregulated the adhesion molecule CD54, the chemokine receptor CCR5 and the activating receptor NKG2C. In remission, these markers were unaltered or marginally altered. All other receptors investigated (NKp30, NKp44, NKp46, NKG2D, DNAM1, 2B4, CRACC, 41BB) remained unchanged. Natural cytotoxicity was not detectable in most patients with active GPA, but was restored in remission.



NK cell numbers correlate inversely with GPA activity. Reduced CD56(dim) NK cells in active GPA have an activated phenotype, which intriguingly is associated with profound deficiency in cytotoxicity. These data suggest a function for NK cells in the pathogenesis and/or modulation of inflammation in GPA. NK cell numbers, phenotype (CD16, CD69, NKG2C) or overall natural cytotoxicity are promising candidates to serve as clinical biomarkers to determine GPA activity.
Department of Hematology, Oncology and Rheumatology, Internal Medicine V, University Hospital of Heidelberg, Heidelberg, Germany. wolfgang.merkt@med.uni-heidelberg.de.|Leibniz Research Center for Working Environment and Human Factors at TU Dortmund (IfADo), Ardeystraße 67, Dortmund, 44139, Germany. wolfgang.merkt@med.uni-heidelberg.de.
Wolfgang
0000-0002-3108-154X
W
Merkt
Leibniz Research Center for Working Environment and Human Factors at TU Dortmund (IfADo), Ardeystraße 67, Dortmund, 44139, Germany.
Maren
M
Claus
Department of Hematology, Oncology and Rheumatology, Internal Medicine V, University Hospital of Heidelberg, Heidelberg, Germany.
Norbert
N
Blank
Department of Hematology, Oncology and Rheumatology, Internal Medicine V, University Hospital of Heidelberg, Heidelberg, Germany.
Michael
M
Hundemer
Innate Immunity Group, German Cancer Research Center, Heidelberg, Germany.
Adelheid
A
Cerwenka
Department of Hematology, Oncology and Rheumatology, Internal Medicine V, University Hospital of Heidelberg, Heidelberg, Germany.
Hanns-Martin
HM
Lorenz
Leibniz Research Center for Working Environment and Human Factors at TU Dortmund (IfADo), Ardeystraße 67, Dortmund, 44139, Germany. watzl@ifado.de.
Carsten
C
Watzl
D000328:Adult; D000368:Aged; D019002:CD56 Antigen / Q000276:immunology; D015331:Cohort Studies; D005260:Female; D005434:Flow Cytometry; D014890:Granulomatosis with Polyangiitis / Q000276:immunology*; D006801:Humans; D007694:Killer Cells, Natural / Q000276:immunology*; D016131:Lymphocyte Subsets / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D010641:Phenotype
D019002:CD56 Antigen; C522918:NCAM1 protein, human
CCR5; CD16; CD54; Fc receptor; Granulomatosis with polyangiitis; NKG2C; Natural cytotoxicity; Natural killer cells; Vasculitis