| 1. |
- Enqvist, Monika
(author)
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Mechanisms influencing natural killer cell recognition of tumour cells
- 2016
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Doctoral thesis (other academic/artistic)abstract
- Natural killer (NK) cells are part of our innate immune defence against virus-infected and transformed cells. Through a yet undefined mechanism, expression of inhibitory receptors for self-HLA class I molecules endow NK cells with increased functionality. The process leading to gain of function through inhibition is known as NK cell education. In the first part of this thesis the cellular mechanisms behind this phenomenon were studied. We found that the expression levels of the activation/adhesion molecule DNAM-1 correlated with the education state in NK cells. Our results suggest that DNAM-1 together with coordinated conformational changes in the adhesion molecule LFA-1 may contribute to the heightened effector functions in educated NK cells. A decreased NK cell function has been previously associated with impaired immune surveillance and a higher risk for developing cancer. By studying samples from patients diagnosed with myelodysplastic syndromes (MDS), we found that NK cells in the bone marrow were phenotypically altered and functionally impaired. Two activating receptors, DNAM-1 and NKG2D were decreased, and the ability to recognise and kill MDS blast cells compromised. The phenotypic alterations correlated with the frequency of leukemic blast cells suggesting that the immune dysfunction progress with the severity of the disease. In one part of this thesis possibilities to improve tumour cell recognition by NK cells were examined. Oxidative stress induced by selenite in a tumour cell line lowered the surface expression of HLA-E, which is a ligand for inhibitory NKG2A receptors expressed by a large proportion of human NK cells. The downregulation of HLA-E led to increased NK cell detection and killing of the tumour cells by NKG2A+ NK cells. Therapeutic antibodies have led to a paradigm shift in the care of patients with malignant lymphoma. Yet the mechanisms of action and the contribution of discrete immune subsets to the clinical efficacy are largely unknown. One suggested mechanism is NK cell mediated antibody-dependent cellular cytotoxicity. We studied NK cell repertoires in sequential lymph node biopsies from follicular lymphoma patients undergoing treatment with anti-CD20 antibodies. After treatment there was a decrease in peripheral NK cells, and the remaining NK cells from both peripheral blood and tumour-associated lymph nodes were activated. Furthermore, the NK cells showed an altered ability to produce cytokines after in vitro restimulation. In conclusion, the data presented here provide new insights into how NK cells recognise and respond to tumour cells at steady state and in malignant diseases.
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| 2. |
- Enqvist, Monika, et al.
(author)
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Systemic and Intra-Nodal Activation of NK Cells After Rituximab Monotherapy for Follicular Lymphoma.
- 2019
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In: Frontiers in Immunology. - : Frontiers Media SA. - 1664-3224. ; 10
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Journal article (peer-reviewed)abstract
- Monotherapy with the anti-CD20 monoclonal antibody rituximab can induce complete responses (CR) in patients with follicular lymphoma (FL). Resting FcRγIII+ (CD16+) natural killer (NK) cells respond strongly to rituximab-coated target cells in vitro. Yet, the contribution of NK cells in the therapeutic effect in vivo remains unknown. Here, we followed the NK cell repertoire dynamics in the lymph node and systemically during rituximab monotherapy in patients with FL. At baseline, NK cells in the tumor lymph node had a naïve phenotype albeit they were more differentiated than NK cells derived from control tonsils as determined by the frequency of CD56dim NK cells and the expression of killer cell immunoglobulin-like receptors (KIR), CD57 and CD16. Rituximab therapy induced a rapid drop in NK cell numbers coinciding with a relative increase in the frequency of Ki67+ NK cells both in the lymph node and peripheral blood. The Ki67+ NK cells had slightly increased expression of CD16, CD57 and higher levels of granzyme A and perforin. The in vivo activation of NK cells was paralleled by a temporary loss of in vitro functionality, primarily manifested as decreased IFNγ production in response to rituximab-coated targets. However, patients with pre-existing NKG2C+ adaptive NK cell subsets showed less Ki67 upregulation and were refractory to the loss of functionality. These data reveal variable imprints of rituximab monotherapy on the NK cell repertoire, which may depend on pre-existing repertoire diversity.
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| 3. |
- Forslund, Elin, et al.
(author)
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Microchip-Based Single-Cell Imaging Reveals That CD56(dim) CD57(-)KIR(-)NKG2A(+) NK Cells Have More Dynamic Migration Associated with Increased Target Cell Conjugation and Probability of Killing Compared to CD56(dim)CD57(-)KIR(-)NKG2A(-) NK Cells
- 2015
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In: Journal of Immunology. - : The American Association of Immunologists. - 0022-1767 .- 1550-6606. ; 195:7, s. 3374-3381
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Journal article (peer-reviewed)abstract
- NK cells are functionally educated by self-MHC specific receptors, including the inhibitory killer cell Ig-like receptors (KIRs) and the lectin-like CD94/NKG2A heterodimer. Little is known about how NK cell education influences qualitative aspects of cytotoxicity such as migration behavior and efficacy of activation and killing at the single-cell level. In this study, we have compared the behavior of FACS-sorted CD56(dim)CD57(-)KIR(-)NKG2A(+) (NKG2A(+)) and CD56(dim)CD57(-)KIR(-)NKG2A(+) (lacking inhibitory receptors; IR-) human NK cells by quantifying migration, cytotoxicity, and contact dynamics using microchip-based live cell imaging. NKG2A(+) NK cells displayed a more dynamic migration behavior and made more contacts with target cells than IR-NK cells. NKG2A(+) NK cells also more frequently killed the target cells once a conjugate had been formed. NK cells with serial killing capacity were primarily found among NKG2A(+) NK cells. Conjugates involving IR- NK cells were generally more short-lived and IR- NK cells did not become activated to the same extent as NKG2A(+) NK cells when in contact with target cells, as evident by their reduced spreading response. In contrast, NKG2A(+) and IR- NK cells showed similar dynamics in terms of duration of conjugation periods and NK cell spreading response in conjugates that led to killing. Taken together, these observations suggest that the high killing capacity of NKG2A(+) NK cells is linked to processes regulating events in the recognition phase of NK-target cell contact rather than events after cytotoxicity has been triggered.
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| 4. |
- Vanherberghen, Bruno, et al.
(author)
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Classification of human natural killer cells based on migration behavior and cytotoxic response
- 2013
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In: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 121:8, s. 1326-1334
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Journal article (peer-reviewed)abstract
- Despite intense scrutiny of the molecular interactions between natural killer (NK) and target cells, few studies have been devoted to dissection of the basic functional heterogeneity in individual NK cell behavior. Using a microchip-based, time-lapse imaging approach allowing the entire contact history of each NK cell to be recorded, in the present study, we were able to quantify how the cytotoxic response varied between individual NK cells. Strikingly, approximately half of the NK cells did not kill any target cells at all, whereas a minority of NK cells was responsible for a majority of the target cell deaths. These dynamic cytotoxicity data allowed categorization of NK cells into 5 distinct classes. A small but particularly active subclass of NK cells killed several target cells in a consecutive fashion. These "serial killers" delivered their lytic hits faster and induced faster target cell death than other NK cells. Fast, necrotic target cell death was correlated with the amount of perforin released by the NK cells. Our data are consistent with a model in which a small fraction of NK cells drives tumor elimination and inflammation.
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