A complexidade do sistema imunológico

Natural Killer Cell Signal Integration Balances Synapse Symmetry and Migration

Fiona J. Culley1¤a, Matthew Johnson1, J. Henry Evans1, Sunil Kumar1, Rupert Crilly1, Juan Casasbuenas1, Tim Schnyder1, Maryam Mehrabi1, Mahendra P. Deonarain1, Dmitry S. Ushakov2, Veronique Braud3, Günter Roth4, Roland Brock5¤b, Karsten Köhler1, Daniel M. Davis1*

1 Division of Cell and Molecular Biology, Imperial College London, London, United Kingdom, 2 National Heart and Lung Institute, Imperial College London, London, United Kingdom, 3 Institut de Pharmacologie Moleculaire et Cellulaire, Centre National de la Recherche Scientifique/Université de Nice-Sophia Antipolis, UMR6097, Valbonne, France, 4 Department of Molecular Biology, Interfacultary Institute for Cell Biology, University of Tübingen, Tübingen, Germany, 5 Department of Biochemistry, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands

Abstract Top

Natural killer (NK) cells discern the health of other cells by recognising the balance of activating and inhibitory ligands expressed by each target cell. However, how the integration of activating and inhibitory signals relates to formation of the NK cell immune synapse remains a central question in our understanding of NK cell recognition. Here we report that ligation of LFA-1 on NK cells induced asymmetrical cell spreading and migration. In contrast, ligation of the activating receptor NKG2D induced symmetrical spreading of ruffled lamellipodia encompassing a dynamic ring of f-actin, concurrent with polarization towards a target cell and a “stop” signal. Ligation of both LFA-1 and NKG2D together resulted in symmetrical spreading but co-ligation of inhibitory receptors reverted NK cells to an asymmetrical migratory configuration leading to inhibitory synapses being smaller and more rapidly disassembled. Using micropatterned activating and inhibitory ligands, signals were found to be continuously and locally integrated during spreading. Together, these data demonstrate that NK cells spread to form large, stable, symmetrical synapses if activating signals dominate, whereas asymmetrical migratory “kinapses” are favoured if inhibitory signals dominate. This clarifies how the integration of activating and inhibitory receptor signals is translated to an appropriate NK cell response.

Author Summary Top

Immune cells survey their local environment and an immunological response can be activated when an appropriate target cell or antigen-presenting cell is recognised by key cell surface molecules. Just how the multitude of protein–protein interactions work to regulate this decision is an ongoing question. Imaging technology has provided key insights, demonstrating that immune cell activation is often accompanied by the segregation of proteins at immune synapses. Natural killer (NK) cells are lymphocytes that can recognise and kill virally infected or tumour-transformed cells via the formation of a synapse that facilitates secretion of cytotoxic granules directed at the target cells. Key to understanding target cell recognition by NK cells is to establish how the balance of activating and inhibitory signals at the synapse leads to an appropriate response, e.g., to kill or spare a target cell. We found that when activating ligands are dominant on a target cell, NK cells stop migrating and spread lamellipodia across the target cell to form a large symmetrical synapse. If inhibitory signals dominate, the symmetry of the NK cell spreading response is broken and the stop signal is reversed, which reduces the time spent in contact with the target cell. Thus, NK cell activating and inhibitory signals regulate NK cell synapse symmetry and migration to determine whether an NK cell will kill or move on.

Citation: Culley FJ, Johnson M, Evans JH, Kumar S, Crilly R, et al. (2009) Natural Killer Cell Signal Integration Balances Synapse Symmetry and Migration. PLoS Biol 7(7): e1000159. doi:10.1371/journal.pbio.1000159

Academic Editor: Philippa Marrack, National Jewish Medical and Research Center/Howard Hughes Medical Institute, United States of America

Received: March 5, 2009; Accepted: June 12, 2009; Published: July 28, 2009

Copyright: © 2009 Culley et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: This work was funded by a Lister Institute Research Prize for Preventive Medicine (www.lister-institute.org.uk), The Royal Society (royalsociety.org), the Medical Research Council (www.mrc.ac.uk; G0500563), the Biotechnology and Biological Sciences Research Council (www.bbsrc.ac.uk; BB/D011663/1), and a Wolfson Royal Society Research Merit Award (royalsociety.org) to DMD. RB acknowledges support from the Volkswagen-Foundation (www.volkswagenstiftung.de; “Nachwuchsgruppen an Universitäten” I/77 472) and the German Ministry for Education and Research (www.bmbf.de; Technical applications of self organization, 13N9127). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

Abbreviations: IFNγ, interferon gamma; IRM, interference reflection microscopy; KIR, killer-cell immunoglobulin-like receptor; LILR, leukocyte Ig-like receptor; MTOC, microtubule organizing centre; NK cell, natural killer cell; PDMS, polydimethylsiloxane; SD, standard deviation; TIRF, total internal reflection fluorescence; YFP, yellow fluorescent protein

* E-mail: d.davis@imperial.ac.uk

¤a Current address: Department of Respiratory Medicine, National Heart and Lung Institute, Faculty of Medicine, Imperial College London, Norfolk Place, London, United Kingdom

¤b Current address: Department of Microsystems Engineering (IMTEK), University of Freiburg, Freiburg, Germany

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