D.M.O. acknowledges European Research Council grant No. 337187 and the Marie-Curie Career Integration Grant No. 334303. P.W.W. acknowledges the Natural Sciences and Engineering Research Council of Canada's Discovery Grant program.

Note: Stages 1 and 2 take place before the day of imaging; ensure all media and supplements to be used before or on the day of imaging are equilibrated. Equilibration is achieved through warming of media and supplements to 37 &#176;C in an incubator set to 5% CO2. All cell culture work and coverslip plating steps take place in sterile conditions under a laminar flow hood.
1. Cell Transfection
<ol>
	<li>Transfect the T cells to be imaged 24 hr before the experiment with a plasmid e...

<ol>
	<li>Monks, C., Freiberg, B., Kupfer, H., Sciaky, N., Kupfer, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-dimensional+segregation+of+supramolecular+activation+clusters+in+T+cells.">Three-dimensional segregation of supramolecular activation clusters in T cells.</a> Nature. 395, 82-86 (1998).</li><li>Lanzavecchia, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Antigen-specific+interaction+between+T+and+B+cells.">Antigen-specific interaction between T and B cells.</a> Nature. 314, 537-539 (1985).</li><li>Grakoui, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+immunological+synapse:+a+molecular+machine+controlling+T+cell+activation.">The immunological synapse: a molecular machine controlling T cell activation.</a> Science. 285 (5425), 221-227 (1999).</li><li>Delon, J., Bercovici, N., Liblau, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imaging+antigen+recognition+by+naive+CD4++T+cells:+compulsory+cytoskeletal+alterations+for+the+triggering+of+an+intracellular+calcium+response.">Imaging antigen recognition by naive CD4+ T cells: compulsory cytoskeletal alterations for the triggering of an intracellular calcium response.</a> European journal of Immunology. 28 (2), 716-729 (1998).</li><li>Varma, R., Campi, G., Yokosuka, T., Saito, T., Dustin, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=T+Cell+Receptor-Proximal+Signals+Are+Sustained+in+Peripheral+Microclusters+and+Terminated+in+the+Central+Supramolecular+Activation+Cluster.">T Cell Receptor-Proximal Signals Are Sustained in Peripheral Microclusters and Terminated in the Central Supramolecular Activation Cluster.</a> Immunity. 25 (1), 117-127 (2006).</li><li>Rust, M. J., Bates, M., Zhuang, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sub-diffraction-limit+imaging+by+stochastic+optical+reconstruction+microscopy+(STORM).">Sub-diffraction-limit imaging by stochastic optical reconstruction microscopy (STORM).</a> Nature methods. 3, 793-796 (2006).</li><li>Betzig, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imaging+intracellular+fluorescent+proteins+at+nanometer+resolution.">Imaging intracellular fluorescent proteins at nanometer resolution.</a> Science. 313 (5793), 1642-1645 (2006).</li><li>Klar, T. A., Jakobs, S., Dyba, M., Egner, A., Hell, S. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fluorescence+microscopy+with+diffraction+resolution+barrier+broken+by+stimulated+emission.">Fluorescence microscopy with diffraction resolution barrier broken by stimulated emission.</a> Proceedings of the National Academy of Sciences. 97 (15), 8206-8210 (2000).</li><li>Gustafsson, M. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surpassing+the+lateral+resolution+limit+by+a+factor+of+two+using+structured+illumination+microscopy.">Surpassing the lateral resolution limit by a factor of two using structured illumination microscopy.</a> Journal of Microscopy. 198 (2), 82-87 (2000).</li><li>Hebert, B., Costantino, S., Wiseman, P. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spatiotemporal+image+correlation+spectroscopy+(STICS)+theory,+verification,+and+application+to+protein+velocity+mapping+in+living+CHO+cells.">Spatiotemporal image correlation spectroscopy (STICS) theory, verification, and application to protein velocity mapping in living CHO cells.</a> Biophysical Journal. 88 (5), 3601-3614 (2005).</li><li>Ashdown, G. W., Cope, A., Wiseman, P. W., Owen, D. 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The authors declare that they have no competing financial interests.

This technique will allow researchers to image and quantify previously unresolvable details in cells expressing fluorescence. In our results we show that F-actin flows in a symmetrical fashion from the cell periphery towards the cell center in the T cell IS. These findings are consistent with previous results from 1D line profile kymograph data13 and extend the capacity of analysis to 2D and super-resolution data.
The presented technique is a progression from kymograph imaging which...

The goal of the experiment is to image and characterize the molecular flow of filamentous- (F-) actin in living T cells, beyond the diffraction limit in order to establish flow direction and magnitude during immunological synapse (IS) formation. This technique will be carried out using a structured illumination microscope (SIM) in total internal reflection fluorescence (TIRF) mode, imaging Jurkat T-cells forming an artificial synapse on activating coverslips coated with anti-CD3- and anti-CD28 antibodies. The IS forms between a T cell and its target; an antigen presenting cell (APC) upon T cell receptor (TCR) activation1,2. As this is the first step in determining whether the adaptive immune system generates an immune response to an infection, the consequences of incorrect responsiveness to stimuli can cause a number of diseases. The importance of the T cell-APC interaction is well documented, however, the role(s) of the mature IS after initial TCR signal internalization are yet to be fully understood.
As the cytoskeleton is thought to aid two processes linked to TCR activation (the movement of molecules at the plasma membrane and the control of signaling molecules dependent on the actin cytoskeleton3,4 ), understanding how the cytoskeleton rearranges spatially and temporally will elucidate the steps of molecular reorganization during synapse formation. The retrograde flow of F-actin is thought to corral TCR clusters towards the center of the immunological synapse, this translocation is believed to be vital for signal cessation and recycling; aiding the fine balance of T cell activation5.
While standard fluorescence microscopy is a flexible tool that continues to provide insight about many biological events including cell-cell interactions, it is limited by the system&#39;s ability to accurately resolve multiple fluorophores residing closer than the diffraction limit (&#8776;200 nm) of each other. As many molecular events within cells involve dense populations of molecules and exhibit dynamic rearrangement either in quiescence or upon specific stimulation, conventional light microscopy does not provide the full picture.
The use of super resolution imaging has allowed researchers to circumvent the diffraction limit using a variety of techniques. Single molecule localization microscopy (SMLM) such as PALM and STORM6,7 has the ability to resolve the location of molecules up to a precision of around 20 nm, however, these techniques rely on long acquisition times, building up an image over many frames. Generally this requires samples to be fixed or for structures to exhibit low mobility so single fluorophores are not misinterpreted as multiple points. While stimulated emission depletion (STED) imaging allows super-resolution through very selective confocal excitation8, the required scanning approach can be slow over whole cell fields of view. STED also demonstrates significant phototoxicity for higher resolutions due to the increase in power of the depletion beam.
Structured illumination microscopy (SIM9) provides an alternative to these methods, capable of doubling the resolution of a standard fluorescence microscope and is more compatible with live cell imaging than current SMLM techniques. It uses lower laser powers, on a wide-field system for whole-cell fields of view; providing increased acquisition speeds, and is compatible with standard fluorophore labelling. The wide-field nature of SIM also permits the utilization of total internal reflection fluorescence (TIRF) for highly selective excitation, with penetration depths in the axial dimension of &#60;100 nm.
Image correlation spectroscopy (ICS) is a method of correlating fluctuations in fluorescence intensity. An evolution of ICS; Spatio-temporal image correlation spectroscopy (STICS10) correlates intracellular fluorescent signals in time and space. By correlating pixel intensities with surrounding pixels in lagging frames via a correlation function, information is gained regarding flow speeds and directionality. To ensure static objects do not interfere with the STICS analysis, an immobile object filter is implemented, which works by subtracting a moving average of the pixel intensities.
The technique presented here is believed to be the first demonstration of image correlation spectroscopy being applied to super-resolution microscopy data to quantify the molecular flow in live cells11. This method improves on diffraction-limited imaging of F-actin flow via STICS analysis12 and would suit researchers who wish to determine two-dimensional molecular flow in live cells, from data acquired at spatial resolutions beyond the diffraction limit of light.

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	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:271px;">Consumables:</td>
			<td style="width:245px;"></td>
			<td style="width:123px;"></td>
			<td style="width:160px;"></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Jurkat E6.1 cells</td>
			<td>APCC</td>
			<td>ATTC TIB-152</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">RPMI</td>
			<td>Life Technologies</td>
			<td>21875-091</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">FBS</td>
			<td>Sigma</td>
			<td>F7524-500ML</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Penicillin-Strepromycin&#160;</td>
			<td>Life Technologies</td>
			<td>15140-122</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">HBSS</td>
			<td>&#160;Life Technologies</td>
			<td>14025-050</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">HEPES</td>
			<td>Life Technologies</td>
			<td>15630-056</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">#1.5 8-well Labtek coverslips</td>
			<td>NUNC, Labtek</td>
			<td>155409</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">LifeAct GFP construct</td>
			<td>Ibidi</td>
			<td>60101</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">OptiMem</td>
			<td>Life Technologies</td>
			<td>51985-042</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">anti-CD3</td>
			<td>Cambridge Bioscience</td>
			<td>317315</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">anti-CD28</td>
			<td>BD Bioscience / Insight Biotechnology</td>
			<td>555725</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">PBS</td>
			<td>Life Technologies</td>
			<td>20012-019</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Lens oil</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Name</td>
			<td>Company</td>
			<td>Catalog number</td>
			<td>Comments</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Equipment:</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Gene Pulsar Xcell System</td>
			<td>BioRad</td>
			<td>165-2660</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Cuvette (0.4cm)</td>
			<td>BioRad</td>
			<td>165-2088</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Centrifuge (5810R)</td>
			<td>Eppendorf&#160;</td>
			<td>5805 000.327</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Centrifuge (Heraeus)</td>
			<td>Biofuge pico</td>
			<td>75003235</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">6 well plate</td>
			<td>Corning</td>
			<td>3516</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Stage-top incubator</td>
			<td>Tokai Hit</td>
			<td>INUH-TIZSH</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Nikon N-SIM microscope</td>
			<td>Nikon</td>
			<td>Contact company</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Nikon Analyse software</td>
			<td>Nikon</td>
			<td>Contact company</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Incubator (190D)</td>
			<td>LEEC</td>
			<td>Contact company</td>
			<td></td>
		</tr>
	</tbody>
</table>

cortical actin flow in t cells quantified by spatio-temporal image correlation spectroscopy of structured illumination microscopy data

Filamentous-actin plays a crucial role in a majority of cell processes including motility and, in immune cells, the formation of a key cell-cell interaction known as the immunological synapse. F-actin is also speculated to play a role in regulating molecular distributions at the membrane of cells including sub-membranous vesicle dynamics and protein clustering. While standard light microscope techniques allow generalized and diffraction-limited observations to be made, many cellular and molecular events including clustering and molecular flow occur in populations at length-scales far below the resolving power of standard light microscopy. By combining total internal reflection fluorescence with the super resolution imaging method structured illumination microscopy, the two-dimensional molecular flow of F-actin at the immune synapse of T cells was recorded. Spatio-temporal image correlation spectroscopy (STICS) was then applied, which generates quantifiable results in the form of velocity histograms and vector maps representing flow directionality and magnitude. This protocol describes the combination of super-resolution imaging and STICS techniques to generate flow vectors at sub-diffraction levels of detail. This technique was used to confirm an actin flow that is symmetrically retrograde and centripetal throughout the periphery of T cells upon synapse formation.

Microscope settings
After successfully achieving all steps the researcher will have accomplished structured illumination (SIM) imaging of F-actin flow in a T cell synapse (Video 1), and quantified this molecular flow by spatio-temporal image correlation spectroscopy (Figure 411). Before recording images, ensure the sample illumination is uniform across the nine raw images and that structured illuminat...

Watch this Scientific Journal Video about Cortical Actin Flow in T Cells Quantified by Spatio-temporal Image Correlation Spectroscopy of Structured Illumination Microscopy Data at JoVE.com

Cortical Actin Flow in T Cells Quantified by Spatio-temporal Image Correlation Spectroscopy of Structured Illumination Microscopy Data

To investigate flow velocities and directionality of filamentous-actin at the T cell immunological synapse, live-cell super-resolution imaging is combined with total internal reflection fluorescence and quantified with spatio-temporal image correlation spectroscopy.

Filamentous-actin plays a crucial role in a majority of cell processes including motility and, in immune cells, the formation of a key cell-cell ...

cortical-actin-flow-t-cells-quantified-spatio-temporal-image

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Immunology and Infection

9.6K Views.  King's College London. To investigate flow velocities and directionality of filamentous-actin at the T cell immunological synapse, live-cell super-resolution imaging is combined with total internal reflection fluorescence and quantified with spatio-temporal image correlation spectroscopy. 