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Autoantibodies to the CD94/NKG2A and CD94/NKG2C receptors in patients with systemic lupus erythematosus
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Rheumatology. niklas.hagberg@medsci.uu.se.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Rheumatology.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Rheumatology.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Objectives: To investigate the occurrence and function of autoantibodies (autoabs) targeting the CD94/NKG2A, CD94/NKG2C or NKG2D receptors in patients with systemic lupus erythematosus (SLE).

Method: Murine Ba/F3 cells transfected with CD94/NKG2A, CD94/NKG2C or NKG2D, and untransfected cells were incubated with sera from 203 patients with SLE and 90 healthy individuals. Binding of immunoglobulin (Ig) to the cells was determined by flow cytometry. Autoabs were characterized with regard to isotype, subclass, λ/κ exclusion and interference with HLA-E-binding. IgG were evaluated for effect on NK cell degranulation in response to HLA-E-transfected K562 target cells, as well as their capacity to induce antibody-dependent cellular cytotoxicity (ADCC). The frequency and phenotype of NK cells from these patients were determined by flow cytometry and the exons encoding NKG2A (KLRC1), NKG2C (KLRC2) and CD94 (KLRD1) were sequenced. The titers of anti-CD94/NKG2A and -CD94/NKG2C autoabs were determined in longitudinally sampled sera and correlated to disease activity (SLEDAI score) and severity (SLICC/ACR damage index).

Results: Seven patients with autoabs targeting the CD94/NKG2A receptor were identified. Two of these patients’ autoabs also recognized the CD94/NKG2C receptor. IgG from six of the patients interfered with the binding of HLA-E to CD94/NKG2A, whereas IgG from one patient increased this binding. Of the two patients with anti-CD94/NKG2C autoabs, IgG from one patient blocked, and IgG from the other patient stabilized the binding of HLA-E to CD94/NKG2C. Anti-CD94/NKG2A autoabs abrogated the HLA-E-mediated inhibition of NK cell cytotoxicity by CD94/NKG2A+ NK cells, whereas anti-CD94/NKG2C autoabs interfered with the HLA-E-mediated increased cytotoxicity of CD94/NKG2C+ NK cells. Furthermore, these autoabs induced ADCC of CD94/NKG2A- and CD94/NKG2C-expressing target cells. No uncommon non-synonymous sequence variations were found in the genes encoding NKG2A, NKG2C or CD94.  The titers of anti-CD94/NKG2A and -CD94/NKG2C autoabs were associated to the SLEDAI score.

Conclusions: Autoabs targeting the CD94/NKG2A or the CD94/NKG2C receptor are found in a subset of patients with SLE. These autoabs affects the cytotoxicity of NK cells, mediate ADCC in vitro and their titers are associated to the disease activity and a more severe SLE phenotype. Consequently, anti-CD94/NKG2A and anti-CD94/NKG2C autoabs may contribute to the pathogenesis of SLE and our findings highlight the possible importance of NK cells in the SLE disease process.

Keywords [en]
Systemic lupus erythematosus, Autoantibodies, Natural killer cell, CD94/NKG2A, CD94/NKG2C, HLA-E
National Category
Immunology in the medical area
Research subject
Medical Science
Identifiers
URN: urn:nbn:se:uu:diva-213672OAI: oai:DiVA.org:uu-213672DiVA, id: diva2:683120
Funder
Knut and Alice Wallenberg FoundationSwedish Research CouncilAvailable from: 2014-01-02 Created: 2014-01-02 Last updated: 2018-01-11
In thesis
1. The Role of Plasmacytoid Dendritic Cells and Natural Killer Cells in Systemic Lupus Erythematosus
Open this publication in new window or tab >>The Role of Plasmacytoid Dendritic Cells and Natural Killer Cells in Systemic Lupus Erythematosus
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by autoantibody production, which can eventually lead to immune complex (IC)-mediated organ damage. Due to the stimulation of plasmacytoid dendritic cells (pDC) by nucleic acid-containing ICs (DNA- or RNA-IC), patients with SLE have an ongoing interferon (IFN)-α production. IFN-α induces a general activation of the immune system that may initiate or propagate an autoimmune process if not properly regulated. Previous studies have shown that natural killer (NK) cells potently enhance the IFN-α production by pDCs.

In study I, the mechanisms behind the NK cell-mediated increased IFN-α production by RNA-IC-stimulated pDCs were investigated. ICs triggered CD56dim NK cells via FcγRIIIA to the secretion of cytokines (e.g. MIP-1β) that promoted IFN-α production. Additionally, an LFA-1-dependent cell-cell interaction between pDCs and NK cells strongly contributed to the increased production of IFN-α. In study II, the RNA-IC-induced regulation of surface molecules on pDCs and NK cells was investigated. The expression of CD319 and CD229, which are two SLAM family receptors genetically associated with SLE, was induced on pDCs and NK cells by RNA-IC. IFN-α-producing pDCs displayed an increased expression of CD319 and CD229, whereas pDCs from patients with SLE had a decreased expression of CD319. In study III, we serendipitously identified an SLE patient harboring autoantibodies to the NK cell receptor CD94/NKG2A. In study IV, sera from 203 patients with SLE were analyzed for autoantibodies to the CD94/NKG2A, CD94/NKG2C and NKG2D receptors. Seven patients harbored anti-CD94/NKG2A autoantibodies, and two of these patient’s autoantibodies also reacted with CD94/NKG2C. Anti-CD94/NKG2A and anti-CD94/NKG2C autoantibodies both interfered with the HLA-E-mediated regulation of NK cell cytotoxicity, and facilitated the elimination of target cells expressing these receptors. Furthermore, these autoantibodies were found in a group of severely diseased SLE patients and their titers closely followed disease activity.

In conclusion, this thesis provides insights to molecular mechanisms whereby NK cells regulate the IFN-α production, it further links the SLAM receptors to SLE, and it describes novel autoantibodies to receptors regulating NK cell cytotoxicity. Together these findings strengthen the assumption that NK cells are involved in the pathogenesis of SLE.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2014. p. 73
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 963
Keywords
Systemic lupus erythematosus, plasmacytoid dendritic cells, natural killer cells, type I interferon, immune complex, SLAM receptors, autoantibodies, CD94/NKG2A, CD94/NKG2C
National Category
Rheumatology and Autoimmunity
Research subject
Medical Science; Immunology
Identifiers
urn:nbn:se:uu:diva-213674 (URN)978-91-554-8837-6 (ISBN)
Public defence
2014-02-21, Rudbecksalen, Rudbecklaboratoriet, Dag Hammarskjölds väg 20, Uppsala, 09:15 (English)
Opponent
Supervisors
Funder
Swedish Research Council, A0258801Knut and Alice Wallenberg Foundation, 2011.0073Science for Life Laboratory - a national resource center for high-throughput molecular bioscience
Available from: 2014-01-28 Created: 2014-01-02 Last updated: 2014-02-10

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