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| 2. |
- Benninger, Richard K. P., et al.
(författare)
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Live Cell Linear Dichroism Imaging Reveals Extensive Membrane Ruffling within the Docking Structure of Natural Killer Cell Immune Synapses
- 2009
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Ingår i: Biophysical Journal. - : Elsevier BV. - 0006-3495 .- 1542-0086. ; 96:2, s. L13-L15
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Tidskriftsartikel (refereegranskat)abstract
- We have applied fluorescence imaging of two-photon linear dichroism to measure the subresolution organization of the cell membrane during formation of the activating (cytolytic) natural killer (NK) cell immune synapse (IS). This approach revealed that the NK cell plasma membrane is convoluted into ruffles at the periphery, but not in the center of a mature cytolytic NK cell IS. Time-lapse imaging showed that the membrane ruffles formed at the initial point of contact between NK cells and target cells and then spread radialy across the intercellular contact as the size of the IS increased, becoming absent from the center of the mature synapse. Understanding the role of such extensive membrane ruff ling in the assembly of cytolytic synapses is an intriguing new goal.
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| 3. |
- Karampatzakis, Alexandros, et al.
(författare)
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Antibody Afucosylation Augments CD16-Mediated Serial Killing and IFN gamma Secretion by Human Natural Killer Cells
- 2021
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Ingår i: Frontiers in Immunology. - : Frontiers Media SA. - 1664-3224. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- One mechanism by which monoclonal antibodies (mAb) help treat cancer or autoimmune disease is through triggering antibody-dependent cellular cytotoxicity (ADCC) via CD16 on Natural Killer (NK) cells. Afucosylation is known to increase the affinity of mAbs for CD16 on NK cells and here, we set out to assess how mAb afucosylation affects the dynamics of NK cell interactions, receptor expression and effector functions. An IgG1 version of a clinically important anti-CD20 mAb was compared to its afucosylated counterpart (anti-CD20-AF). Opsonization of CD20-expressing target cells, 721.221 or Daudi, with anti-CD20-AF increased NK cell cytotoxicity and IFN gamma secretion, compared to anti-CD20. The afucosylated mAb also caused a more rapid and greater loss of CD16 from NK cell surfaces. Loss of CD16 has recently been shown to be important for NK cell detachment and sequential engagement of multiple target cells. Here, live-cell time-lapse microscopy of individual cell-cell interactions in an aqueous environment and a three-dimensional matrix, revealed that anti-CD20-AF induced more rapid killing of opsonized target cells. In addition, NK cells detached more quickly from target cells opsonized with anti-CD20-AF compared to anti-CD20, which increased engagement of multiple targets and enabled a greater proportion of NK cells to perform serial killing. Inhibition of CD16 shedding with TAPI-0 led to reduced detachment and serial killing. Thus, disassembly of the immune synapse caused by loss of cell surface CD16 is a factor determining the efficiency of ADCC and antibody afucosylation alters the dynamics of intercellular interactions to boost serial killing.
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| 4. |
- McCann, Fiona E., et al.
(författare)
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The activating NKG2D ligand MHC class I-related chain a transfers from target cells to NK cells in a manner that allows functional consequences
- 2007
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Ingår i: Journal of Immunology. - : The American Association of Immunologists. - 0022-1767 .- 1550-6606. ; 178:6, s. 3418-3426
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Tidskriftsartikel (refereegranskat)abstract
- Recently, it has become apparent that surface proteins commonly transfer between immune cells in contact. Inhibitory receptors and ligands exchange between cells during NK cell surveillance and we report here that NK cells also acquire activating ligands from target cells. Specifically, the stress-inducible activating ligand for NKG2D, MHC class I-related chain A (MICA), transferred to NK cells upon conjugation with MICA-expressing target cells. Acquisition of MICA from target cells was dependent on cell contact and occurred after accumulation of MICA at the immunological synapse. Moreover, transfer of MICA was facilitated by specific molecular recognition via NKG2D and augmented by Src kinase signaling. Importantly, MICA associated with its new host NK cell membrane in an orientation that allowed engagement with NKG2D in trans and indeed could down-regulate NKG2D in subsequent homotypic interactions with other NK cells. MICA captured from target cells could subsequently transfer between NK cells and, more importantly, NK cell degranulation was triggered in such NK cell-NK cell interactions. Thus, NK cells can influence other NK cells with proteins acquired from target cells and our data specifically suggest that NK cells could lyse other NK cells upon recognition of activating ligands acquired from target cells. This mechanism could constitute an important function for immunoregulation of NK cell activity.
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| 5. |
- Srpan, Katja, et al.
(författare)
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Shedding of CD16 disassembles the NK cell immune synapse and boosts serial engagement of target cells
- 2018
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Ingår i: Journal of Cell Biology. - : Rockefeller University Press. - 0021-9525 .- 1540-8140. ; 217:9, s. 3267-3283
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Tidskriftsartikel (refereegranskat)abstract
- Natural Killer (NK) cells can engage multiple virally infected or tumor cells sequentially and deliver perforin for cytolytic killing of these targets. Using microscopy to visualize degranulation from individual NK cells, we found that repeated activation via the Fc receptor CD16 decreased the amount of perforin secreted. However, perforin secretion was restored upon subsequent activation via a different activating receptor, NKG2D. Repeated stimulation via NKG2D also decreased perforin secretion, but this was not rescued by stimulation via CD16. These different outcomes of sequential stimulation could be accounted for by shedding of CD16 being triggered by cellular activation. The use of pharmacological inhibitors and NK cells transfected to express a noncleavable form of CD16 revealed that CD16 shedding also increased NK cell motility and facilitated detachment of NK cells from target cells. Disassembly of the immune synapse caused by CD16 shedding aided NK cell survival and boosted serial engagement of target cells. Thus, counterintuitively, shedding of CD16 may positively impact immune responses.
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| 6. |
- Tuomela, Karoliina, et al.
(författare)
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Radiotherapy transiently reduces the sensitivity of cancer cells to lymphocyte cytotoxicity
- 2022
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 119:3, s. e2111900119-
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Tidskriftsartikel (refereegranskat)abstract
- The impact of radiotherapy on the interaction between immune cells and cancer cells is important not least because radiotherapy can be used alongside immunotherapy as a cancer treatment. Unexpectedly, we found that X-ray irradiation of cancer cells induced significant resistance to natural killer (NK) cell killing. This was true across a wide variety of cancer-cell types as well as for antibody-dependent cellular cytotoxicity. Resistance appeared 72 h postirradiation and persisted for 2 wk. Resistance could also occur independently of radiotherapy through pharmacologically induced cell-cycle arrest. Crucially, multiple steps in NK-cell engagement, synapse assembly, and activation were unaffected by target cell irradiation. Instead, radiotherapy caused profound resistance to perforin-induced calcium flux and lysis. Resistance also occurred to a structurally similar bacterial toxin, streptolysin O. Radiotherapy did not affect the binding of pore-forming proteins at the cell surface or membrane repair. Rather, irradiation instigated a defect in functional pore formation, consistent with phosphatidylserine-mediated perforin inhibition. In vivo, radiotherapy also led to a significant reduction in NK cell-mediated clearance of cancer cells. Radiotherapy-induced resistance to perforin also constrained chimeric antigen receptor T-cell cytotoxicity. Together, these data establish a treatment-induced resistance to lymphocyte cytotoxicity that is important to consider in the design of radiotherapy-immunotherapy protocols.
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| 7. |
- Walwyn-Brown, Katherine, et al.
(författare)
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Human NK Cells Lyse Th2-Polarizing Dendritic Cells via NKp30 and DNAM-1
- 2018
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Ingår i: Journal of Immunology. - : The American Association of Immunologists. - 0022-1767 .- 1550-6606. ; 201:7, s. 2028-2041
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Tidskriftsartikel (refereegranskat)abstract
- Cross-talk between NK cells and dendritic cells (DCs) is important in Th1 immune responses, including antitumor immunity and responses to infections. DCs also play a crucial role in polarizing Th2 immunity, but the impact of NK cell-DC interactions in this context remains unknown. In this study, we stimulated human monocyte-derived DCs in vitro with different pathogen-associated molecules: LPS or polyinosinic-polycytidylic acid, which polarize a Th1 response, or soluble egg Ag from the helminth worm Schistosoma mansoni, a potent Th2-inducing Ag. Th2-polarizing DCs were functionally distinguishable from Th1-polarizing DCs, and both showed distinct morphology and dynamics from immature DCs. We then assessed the outcome of autologous NK cells interacting with these differently stimulated DCs. Confocal microscopy showed polarization of the NK cell microtubule organizing center and accumulation of LFA-1 at contacts between NK cells and immature or Th2-polarizing DCs but not Th1-polarizing DCs, indicative of the assembly of an activating immune synapse. Autologous NK cells lysed immature DCs but not DCs treated with LPS or polyinosinic-polycytidylic acid as reported previously. In this study, we demonstrated that NK cells also degranulated in the presence of Th2-polarizing DCs. Moreover, time-lapse live-cell microscopy showed that DCs that had internalized fluorescently labeled soluble egg Ag were efficiently lysed. Ab blockade of NK cell-activating receptors NKp30 or DNAM-1 abrogated NK cell lysis of Th2-polarizing DCs. Thus, these data indicate a previously unrecognized role of NK cell cytotoxicity and NK cell-activating receptors NKp30 and DNAM-1 in restricting the pool of DCs involved in Th2 immune responses.
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| 8. |
- Önfelt, Björn, et al.
(författare)
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Structurally distinct membrane nanotubes between human macrophages support long-distance vesicular traffic or surfing of bacteria
- 2006
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Ingår i: Journal of Immunology. - : The American Association of Immunologists. - 0022-1767 .- 1550-6606. ; 177:12, s. 8476-8483
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Tidskriftsartikel (refereegranskat)abstract
- We report that two classes of membrane nanotubes between human monocyte-derived macrophages can be distinguished by their cytoskeletal structure and their functional properties. Thin membrane nanotubes contained only F-actin, whereas thicker nanotubes, i.e., those > similar to 0.7 mu m in diameter, contained both F-actin and microtubules. Bacteria could be trapped and surf along thin, but not thick, membrane nanotubes toward connected macrophage cell bodies. Once at the cell body, bacteria could then be phagocytosed. The movement of bacteria is aided by a constitutive flow of the nanotube surface because streptavidin-coated beads were similarly able to traffic along nanotubes between surface-biotinylated macrophages. Mitochondria. and intracellular vesicles, including late endosomes and lysosomes, could be detected within thick, but not thin, membrane nanotubes. Analysis from kymographs demonstrated that vesicles moved in a stepwise, bidirectional manner at similar to 1 mu m/s, consistent with their traffic being mediated by the microtubules found only in thick nanotubes. Vesicular traffic in thick nanotubes and surfing of beads along thin nanotubes were both stopped upon the addition of azide, demonstrating that both processes require ATP. However, microtubule destabilizing agents colchicine or nocodazole abrogated vesicular transport but not the flow of the nanotube surface, confirming that distinct cytoskeletal structures of nanotubes give rise to different functional properties. Thus, membrane nanotubes between macrophages are more complex than unvarying ubiquitous membrane tethers and facilitate several means for distal interactions between immune cells.
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