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The Role of Plasmacytoid Dendritic Cells and Natural Killer Cells in Systemic Lupus Erythematosus
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Rheumatology.
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. , 73 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 963
Keyword [en]
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: urn:nbn:se:uu:diva-213674ISBN: 978-91-554-8837-6 (print)OAI: oai:DiVA.org:uu-213674DiVA: diva2:684301
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
List of papers
1. IFN-α Production by Plasmacytoid Dendritic Cells Stimulated with RNA-Containing Immune Complexes Is Promoted by NK Cells via MIP-1β and LFA-1
Open this publication in new window or tab >>IFN-α Production by Plasmacytoid Dendritic Cells Stimulated with RNA-Containing Immune Complexes Is Promoted by NK Cells via MIP-1β and LFA-1
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2011 (English)In: Journal of Immunology, ISSN 0022-1767, E-ISSN 1550-6606, Vol. 186, no 9, 5085-5094 p.Article in journal (Refereed) Published
Abstract [en]

Several systemic autoimmune diseases display a prominent IFN signature. This is caused by a continuous IFN-α production by plasmacytoid dendritic cells (pDCs), which are activated by immune complexes (ICs) containing nucleic acid. The IFN-α production by pDCs stimulated with RNA-containing IC (RNA-IC) consisting of anti-RNP autoantibodies and U1 small nuclear ribonucleoprotein particles was recently shown to be inhibited by monocytes, but enhanced by NK cells. The inhibitory effect of monocytes was mediated by TNF-α, PGE2, and reactive oxygen species, but the mechanisms for the NK cell-mediated increase in IFN-α production remained unclear. In this study, we investigated the mechanisms whereby NK cells increase the RNA-IC–induced IFN-α production by pDCs. Furthermore, NK cells from patients with systemic lupus erythematosus (SLE) were evaluated for their capacity to promote IFN-α production. We found that CD56dim NK cells could increase IFN-α production >1000-fold after RNA-IC activation, whereas CD56bright NK cells required costimulation by IL-12 and IL-18 to promote IFN-α production. NK cells produced MIP-1α, MIP-1β, RANTES, IFN-γ, and TNF-α via RNA-IC–mediated FcγRIIIA activation. The IFN-α production in pDCs was promoted by NK cells via MIP-1β secretion and LFA-mediated cell–cell contact. Moreover, NK cells from SLE patients displayed a reduced capacity to promote the RNA-IC–induced IFN-α production, which could be restored by exogenous IL-12 and IL-18. Thus, different molecular mechanisms can mediate the NK cell-dependent increase in IFN-α production by RNA-IC–stimulated pDCs, and our study suggests that the possibility to therapeutically target the NK–pDC axis in IFN-α–driven autoimmune diseases such as SLE should be investigated.

Keyword
interferon, plasmacytoid dendritic cells, MIP-1beta, NK cells
National Category
Rheumatology and Autoimmunity
Research subject
Medicine
Identifiers
urn:nbn:se:uu:diva-150274 (URN)10.4049/jimmunol.1003349 (DOI)000289679600011 ()21430220 (PubMedID)
Available from: 2011-03-29 Created: 2011-03-29 Last updated: 2017-12-11Bibliographically approved
2. Systemic Lupus Erythematosus Immune Complexes Increase the Expression of SLAM Family Members CD319 (CRACC) and CD229 (LY-9) on Plasmacytoid Dendritic Cells and CD319 on CD56(dim) NK Cells
Open this publication in new window or tab >>Systemic Lupus Erythematosus Immune Complexes Increase the Expression of SLAM Family Members CD319 (CRACC) and CD229 (LY-9) on Plasmacytoid Dendritic Cells and CD319 on CD56(dim) NK Cells
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2013 (English)In: Journal of Immunology, ISSN 0022-1767, E-ISSN 1550-6606, Vol. 191, no 6, 2989-2998 p.Article in journal (Refereed) Published
Abstract [en]

Patients with systemic lupus erythematosus (SLE) display an activated type I IFN system due to unceasing IFN-a release from plasmacytoid dendritic cells (pDCs) stimulated by nucleic acid-containing immune complexes (ICs). NK cells strongly promote the IFN-a production by pDCs; therefore, we investigated surface molecules that could be involved in the pDC-NK cell cross-talk. In human PBMCs stimulated with RNA-containing ICs (RNA-ICs), the expression of the signaling lymphocyte activation molecule (SLAM) family receptors CD319 and CD229 on pDCs and CD319 on CD56(dim) NK cells was selectively increased. Upregulation of CD319 and CD229 on RNA-IC-stimulated pDCs was induced by NK cells or cytokines (e. g., GM-CSF, IL-3). IFN-alpha-producing pDCs displayed a higher expression of SLAM molecules compared with IFN-a 2 pDCs. With regard to signaling downstream of SLAM receptors, pDCs expressed SHIP-1, SHP-1, SHP-2, and CSK but lacked SLAM-associated protein (SAP) and Ewing's sarcoma-activated transcript 2 (EAT2), indicating that these receptors may act as inhibitory receptors on pDCs. Furthermore, pDCs from patients with SLE had decreased expression of CD319 on pDCs and CD229 on CD56 dim NK cells, but RNA-IC stimulation increased CD319 and CD229 expression. In conclusion, this study reveals that the expression of the SLAM receptors CD319 and CD229 is regulated on pDCs and NK cells by lupus ICs and that the expression of these receptors is specifically altered in SLE. These results, together with the observed genetic association between the SLAM locus and SLE, suggest a role for CD319 and CD229 in the SLE disease process.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-209160 (URN)10.4049/jimmunol.1301022 (DOI)000324206900016 ()
Available from: 2013-10-15 Created: 2013-10-15 Last updated: 2017-12-06Bibliographically approved
3. Anti-NKG2A autoantibodies in a patient with systemic lupus erythematosus
Open this publication in new window or tab >>Anti-NKG2A autoantibodies in a patient with systemic lupus erythematosus
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2013 (English)In: Rheumatology, ISSN 1462-0324, E-ISSN 1462-0332, Vol. 52, no 10, 1818-1823 p.Article in journal (Refereed) Published
Abstract [en]

Objectives

To characterize a novel anti-NKG2A autoantibody detected in a patient with SLE during a severe flare, and in a cross-sectional study investigate the occurrence of such autoantibodies in patients with SLE and primary SS (pSS).

Methods

Serum or IgG from patients with SLE, pSS and healthy volunteers were assayed for blocking of anti-NKG2A or HLA-E binding to peripheral blood mononuclear cells or CD94/NKG2A- and CD94/NKG2C-transfected Ba/F3 cells. The anti-NKG2A autoantibodies were evaluated for effect on NK cell degranulation in response to HLA-E-transfected K562 cells. IFN-α was determined by an immunoassay and disease activity by the SLEDAI score.

Results

Anti-NKG2A autoantibodies, which blocked binding of HLA-E tetramers to CD94/NKG2A-transfected cells and impaired NKG2A-mediated inhibition of NK cell activation, were observed in a patient with SLE. The presence of anti-NKG2A autoantibodies was associated with high SLE disease activity (SLEDAI score 14 and 16) and increased serum IFN-α. Of 94 SLE, 60 pSS and 30 healthy donor sera, only the index patient serum contained anti-NKG2A autoantibodies.

Conclusion

The presence of autoantibodies targeting NKG2A is a rare event, but when such autoantibodies occur they may promote excessive NK cell function. This can contribute to the pathogenesis by increasing the killing of cells and the release of autoantigens. Our findings highlight the possible importance of NK cells in the SLE disease process.

National Category
Rheumatology and Autoimmunity
Research subject
Medicine
Identifiers
urn:nbn:se:uu:diva-205111 (URN)10.1093/rheumatology/ket220 (DOI)000325997900014 ()23825044 (PubMedID)
Available from: 2013-08-14 Created: 2013-08-14 Last updated: 2017-12-06Bibliographically approved
4. Autoantibodies to the CD94/NKG2A and CD94/NKG2C receptors in patients with systemic lupus erythematosus
Open this publication in new window or tab >>Autoantibodies to the CD94/NKG2A and CD94/NKG2C receptors in patients with systemic lupus erythematosus
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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.

Keyword
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:nbn:se:uu:diva-213672 (URN)
Funder
Knut and Alice Wallenberg FoundationSwedish Research Council
Available from: 2014-01-02 Created: 2014-01-02 Last updated: 2014-02-10

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