| 1. |
- Bryceson, Yenan
(author)
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Triggering and mechanisms of natural killer cell mediated cytotoxicity
- 2008
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Doctoral thesis (other academic/artistic)abstract
- Natural killer (NK) cells are innate immune cells that contribute to defense against infected and transformed cells by target cell killing and cytokine release. In addition, data suggest that NK cells contribute to immune homeostasis and reproduction. In this thesis, we assessed the contribution of individual receptors and intracellular effector molecules to the function of freshly isolated, resting human NK cells. A reductionist approach, using Drosophila cells transfected with ligands for human NK cell receptors, revealed that combinations of synergistic signals from distinct receptors were required to induce efficient NK cell cytotoxicity. Engagement of CD16 by IgG was sufficient to induce degranulation, whereas engagement of LFA-1 by ICAM-1 was sufficient to induce not only adhesion, but also granule polarization. Efficient antibodydependent cellular cytotoxicity required the combination of granule polarization induced by LFA-1 and degranulation induced by CD16. Receptors NKp46, NKG2D, 2B4, DNAM-1, and CD2 have previously been implicated in natural cytotoxicity. Unexpectedly, engagement of these receptors by specific antibodies failed to induce resting NK cell cytotoxicity. For natural cytotoxicity, co-engagement of specific pairwise combinations of activating receptors synergistically induced degranulation and cytokine production. Thus, the term co-activation receptor has been proposed to describe natural cytotoxicity receptors that function as synergistic pairs. KIR2DL4 is an evolutionary conserved member of the KIR family of receptors. Unlike other NK cell receptors, KIR2DL4 was shown to reside in intracellular vesicles. Thus, soluble, but not solid-phase agonists of KIR2DL4, including natural ligand HLA-G, induced cytokine secretion by NK cells. Without eliciting cytotoxicity, this distinctive activation has putative implications for pregnancy. Further, NK cells were assessed from patients diagnosed with familial hemophagocytic lymphohistiocytosis (FHL), an early onset, fatal immunodeficiency syndrome associated to mutations in genes implicated in cellular cytotoxicity. Analysis demonstrated a requirement for Munc13-4 and syntaxin 11 in resting NK cell degranulation. Remarkably, IL-2 stimulation partially restored degranulation and cytotoxicity by syntaxin 11 deficient NK cells. This could explain the later onset and less severe disease progression observed in FHL caused by nonsense mutations in STX11, relative to mutations in PRF1 or UNC13D. In accord, an UNC13D mutation allowing residual degranulation and cytotoxicity was also associated with later disease onset. Our data suggest that the observed defect in NK cell degranulation may contribute to the pathophysiology of FHL, that evaluation of NK cell degranulation in suspected FHL patients may facilitate diagnosis, and that these new insights may offer novel therapeutic possibilities. Our findings provide detailed insight into the molecular triggering and regulation of human NK cell function. Appreciation of the contribution of individual genetic elements to immune function promises increased understanding of disease. Of clinical relevance, new techniques facilitate improved diagnosis, whereas fundamental understanding may assist in development of better treatment.
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| 2. |
- Cichocki, Frank, et al.
(author)
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NK cell development and function - Plasticity and redundancy unleashed.
- 2014
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In: Seminars in Immunology. - : Elsevier BV. - 1096-3618 .- 1044-5323. ; 26:2, s. 114-126
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Research review (peer-reviewed)abstract
- Bone marrow-derived natural killer (NK) cells constitute the major subset of cytotoxic lymphocytes in peripheral blood. They provide innate defense against intracellular infection or malignancy and contribute to immune homeostasis. Large numbers of NK cells are also present in tissues, including the liver and uterus, where they can mediate immunosurveillance but also play important roles in tissue remodeling and vascularization. Here, we review the pathways involved in NK cell lineage commitment and differentiation, discussing relationships to other lymphocyte populations and highlighting genetic determinants. Characterizing NK cells from distinct tissues and during infections have revealed subset specializations, reflecting inherent cellular plasticity. In this context, we discuss how different environmental and inflammatory stimuli may shape NK cells. Particular emphasis is placed on genes identified as being critical for NK cell development, differentiation, and function from studies of model organisms or associations with disease. Such studies are also revealing important cellular redundancies. Here, we provide a view of the genetic framework constraining NK cell development and function, pinpointing molecules required for these processes but also underscoring plasticity and redundancy that may underlie robust immunological function. With this view, built in redundancy may highlight the importance of NK cells to immunity.
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| 3. |
- Consiglio, Camila Rosat, et al.
(author)
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The Immunology of Multisystem Inflammatory Syndrome in Children with COVID-19
- 2020
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In: Cell. - : CELL PRESS. - 0092-8674 .- 1097-4172. ; 183:4, s. 968-981
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Journal article (peer-reviewed)abstract
- Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is typically very mild and often asymptomatic in children. A complication is the rare multisystem inflammatory syndrome in children (MIS-C) associated with COVID-19, presenting 4-6 weeks after infection as high fever, organ dysfunction, and strongly elevated markers of inflammation. The pathogenesis is unclear but has overlapping features with Kawasaki disease suggestive of vasculitis and a likely autoimmune etiology. Weapply systems-level analyses of blood immune cells, cytokines, and autoantibodies in healthy children, children with Kawasaki disease enrolled prior to COVID-19, children infected with SARS-CoV-2, and children presenting with MIS-C. We find that the inflammatory response in MIS-C differs from the cytokine storm of severe acute COVID-19, shares several features with Kawasaki disease, but also differs from this condition with respect to T cell subsets, interleukin (IL)-17A, and biomarkers associated with arterial damage. Finally, autoantibody profiling suggests multiple autoantibodies that could be involved in the pathogenesis of MIS-C.
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| 4. |
- Greenwood, Tatiana von Bahr, et al.
(author)
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Clinical and laboratory signs of haemophagocytic lymphohistiocytosis associated with pandemic influenza A (H1N1) infection in patients needing extracorporeal membrane oxygenation A retrospective observational study
- 2021
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In: European Journal of Anaesthesiology. - : Lippincott Williams & Wilkins. - 0265-0215 .- 1365-2346. ; 38:7, s. 692-701
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Journal article (peer-reviewed)abstract
- BACKGROUND: Severe pandemic influenza has been associated with the hyperinflammatory condition secondary haemophagocytic lymphohistiocytosis (HLH).OBJECTIVES: To determine the frequency, degree, character and possible cause of influenza-associated HLH in critically ill patients with severe acute respiratory distress syndrome due to influenza A (H1N1) infection requiring extracorporeal membrane oxygenation (ECMO) support at our hospital.DESIGN: A retrospective observational study.PATIENTS AND SETTING: Medical data were retrieved retrospectively from 11 consenting patients of thirteen adults infected with pandemic influenza A (H1N1) 2009 requiring ECMO between July 2009 and January 2010 at the ECMO Centre of Karolinska University Hospital, Stockholm, Sweden. All patients were evaluated for HLH using HLH-2004 criteria and HScore.RESULTS: Eleven patients (median age 31 years) were included in the study and all survived. All patients showed signs of multiple organ dysfunction and pronounced inflammation, more severe in the four patients with HLH who had significantly higher peak serum concentrations of ferritin (P = 0.024), alkaline phosphatase (P = 0.012) and gamma-glutamyl transferase (P = 0.024), lower concentration of albumin (P = 0.0086) and more frequently hepatomegaly (P = 0.048). Abnormal lymphocyte cytotoxicity (lytic units <10) and a low proportion of natural killer (NK) cells were observed in three of four patients with HLH. Notably, we found a significant inverse correlation between serum ferritin concentration and NK cell and cytotoxic T lymphocyte percentages (r(s) = -0.74, P = 0.0013 and r(s) = -0.79, P = 0.0025, respectively). One HLH patient received HLH-directed cytotoxic therapy, another intravenous immunoglobulin and the other two no specific HLH-directed therapy.CONCLUSION: Critically ill patients, including healthy young adults, with pandemic influenza may develop HLH and should be monitored for signs of hyperinflammation and increasing organ dysfunction, and evaluated promptly for HLH because HLH-directed therapy may then be beneficial. The association of low NK percentages with hyperferritinaemia may suggest a role for reduced NK cell numbers, possibly also cytotoxic T lymphocytes, and subsequently reduced lymphocyte cytotoxicity, in the pathogenesis of hyperinflammation and secondary HLH.
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| 5. |
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| 6. |
- Hagberg, Niklas, et al.
(author)
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Anti-NKG2A autoantibodies in a patient with systemic lupus erythematosus
- 2013
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In: Rheumatology. - : Oxford University Press (OUP). - 1462-0324 .- 1462-0332. ; 52:10, s. 1818-1823
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Journal article (peer-reviewed)abstract
- ObjectivesTo 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).MethodsSerum 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.ResultsAnti-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.ConclusionThe 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.
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| 7. |
- Hagberg, Niklas, 1977-, et al.
(author)
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Autoantibodies to the CD94/NKG2A and CD94/NKG2C receptors in patients with systemic lupus erythematosus
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Other publication (other academic/artistic)abstract
- 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.
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| 8. |
- Hagberg, Niklas, et al.
(author)
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Functional Anti-CD94/NKG2A and Anti-CD94/NKG2C Autoantibodies in Patients With Systemic Lupus Erythematosus
- 2015
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In: ARTHRITIS & RHEUMATOLOGY. - : Wiley. - 2326-5191 .- 2326-5205. ; 67:4, s. 1000-1011
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Journal article (peer-reviewed)abstract
- Objective. Recently we serendipitously identified a patient with systemic lupus erythematosus (SLE) who was positive for autoantibodies to CD94/natural killer receptor group 2A (NKG2A). The present study was undertaken to investigate the occurrence and function of autoantibodies targeting lectin-like NK cell receptors in SLE. Methods. Sera from 203 SLE patients and 90 healthy individuals were analyzed, by flow cytometry, for Ig binding to Ba/F3 cells transfected with CD94/NKG2A, CD94/NKG2C, or NKG2D. Autoantibodies identified were characterized with regard to interference with HLA-E binding, effect on NK cell activation in response to HLA-E-transfected K562 cells, and capacity to facilitate antibody-dependent cell-mediated cytotoxicity (ADCC). Levels of autoantibodies were determined in longitudinally sampled sera, and correlations with disease activity (SLE Disease Activity Index 2000) and severity (Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index) were investigated. Results. Anti-CD94/NKG2A autoantibodies were identified in 7 SLE patients. The autoantibodies from 6 patients inhibited binding of HLA-E to CD94/NKG2A, whereas those from the seventh patient augmented this binding. Autoantibodies from 2 patients also reacted with the activating receptor CD94/NKG2C, with inhibition of the binding of HLA-E to CD94/NKG2C observed in 1 case and enhancement of this binding in the other. None of the sera contained anti-NKG2D autoantibodies. The levels of anti-CD94/NKG2A and anti-CD94/NKG2C autoantibodies correlated with disease activity and with a more severe SLE phenotype. Mechanistically, anti-CD94/NKG2A and anti-CD94/NKG2C autoantibodies both interfered with HLA-E-mediated regulation of NK cell activation and facilitated the elimination of target cells expressing CD94/NKG2A or CD94/NKG2C through ADCC. Conclusion. Anti-CD94/NKG2A and anti-CD94/NKG2C autoantibodies occur in a subset of patients with clinically active SLE. Given their capacity to deplete certain NK cell subsets and interfere with particular NK cell function, such autoantibodies may promote the pathogenesis of SLE.
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| 9. |
- Hagberg, Niklas, et al.
(author)
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IFN-α Production by Plasmacytoid Dendritic Cells Stimulated with RNA-Containing Immune Complexes Is Promoted by NK Cells via MIP-1β and LFA-1
- 2011
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In: Journal of Immunology. - : The American Association of Immunologists. - 0022-1767 .- 1550-6606. ; 186:9, s. 5085-5094
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Journal article (peer-reviewed)abstract
- 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.
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