Background Dysregulation of Natural Killer (NK) cells has been shown to influence the development of autoimmune diseases1, but their role in Sjögren's syndrome (SS) remain unclear.
Objectives The main goal of our study was to investigate the recruitment and functional relevance of NK cells in the early phases of salivary gland (SG) inflammation in an inducible murine model of SS.
Methods Sialoadenitis was induced in WT-C57BL/6 mice via SG retro-cannulation of 108 pfu/gland of luciferase-encoding adenovirus-5 (AdV). FACS analysis of NK cells (CD45pos/NK1.1pos/CD3neg) was performed in digested SG, while snap-frozen SG tissues were stained for either cytotoxic NK cells (NK1.1pos/CD3neg/Granzyme Bpos) or B (B220pos) and T cells (CD3pos). Negatively selected CFSEpos NK cells from WT-C57BL/6 mice spleens were adoptively transferred in AdV-infected mice to evaluate NK cell recruitment and proliferation in the SG. Virus infected cell clearance by NK cells was assessed with luciferase activity quantification in SG. To achieve NK cell depletion, 200μg of anti-NK1.1 antibody were administered via intraperitoneal injection every 48h. Anti-nuclear antibodies were assessed on Hep-2-coated microscope slides, and anti-AdV antibodies with ELISA assay.
Results AdV infection in SG induced an early NK cell recruitment peaking at 4 days post-cannulation (dpc). This is due to an active NK cell migration to the SG at 1dpc followed by their intra-SG proliferation at 3-5dpc, as shown by cell transfer experiments. NK cells preferentially accumulate before B/T cell aggregates formation. Activating markers NKp46 and CD69 were up regulated from 5dpc onwards when an increased degranulation potential was observed. Accordingly, NK cells, rather then cytotoxic T cells, mainly mediated cytotoxic activity, as measured by granzyme B expression, at 4/5dpc. NK depletion impaired viral control at 3dpc but not at later time-points. Conversely, NK depletion did not affect the formation of SS-like inflammatory foci or lymphoid chemokine expression. Moreover, NK cells did not influence the production of ANA or anti-AdV antibodies.
Conclusions Here we show that NK cells are actively recruited to the inflammatory site of the SG and are critically involved in the early immune control of AdV infection in this organ but are dispensable for the development of SS-like inflammatory foci and autoimmunity.
Schleinitz N1, Vély F, Harlé JR, Vivier E. Natural killer cells in human autoimmune diseases. Immunology. 2010 Dec;131(4):451-8.
Disclosure of Interest None declared
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