Cette recherche a été financée par la Division de la recherche intra-muros de l&#39;Institut national pour l&#39;allergie et des maladies infectieuses, les National Institutes of Health. Nous sommes reconnaissants à Johannes Huppa et Mark Davis pour nous fournir le scFv de H57 utilisé dans ces études. RV tiens à remercier M. Keir Neumann de discussion utile au cours du développement de cette technique.

<ol>
	<li>Call, M. E., Wucherpfennig, K. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+T+cell+receptor:+critical+role+of+the+membrane+environment+in+receptor+assembly+and+function.">The T cell receptor: critical role of the membrane environment in receptor assembly and function.</a> Annu. Rev. Immunol. 23, 101-125 (2005).</li><li>Smith-Garvin, J. E., Koretzky, G. A., Jordan, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=S.T+cell+activation.">S.T cell activation.</a> Annu. Rev. Immunol. 27, 591-619 (2009).</li><li>Bezbradica, J. 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L. <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, 117-127 (2006).</li><li>Yokosuka, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Newly+generated+T+cell+receptor+microclusters+initiate+and+sustain+T+cell+activation+by+recruitment+of+Zap70+and+SLP-76.">Newly generated T cell receptor microclusters initiate and sustain T cell activation by recruitment of Zap70 and SLP-76.</a> Nat. Immunol. 6, 1253-1262 (2005).</li><li>Huppa, J. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=TCR-peptide-MHC+interactions+in+situ+show+accelerated+kinetics+and+increased+affinity.">TCR-peptide-MHC interactions in situ show accelerated kinetics and increased affinity.</a> Nature. 463, 963-967 (2010).</li><li>Tolar, P., Pierce, S. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+conformation-induced+oligomerization+model+for+B+cell+receptor+microclustering+and+signaling.">A conformation-induced oligomerization model for B cell receptor microclustering and signaling.</a> Curr. Top. Microbiol. Immunol. 340, 155-169 (2010).</li><li>Treanor, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+membrane+skeleton+controls+diffusion+dynamics+and+signaling+through+the+B+cell+receptor.">The membrane skeleton controls diffusion dynamics and signaling through the B cell receptor.</a> Immunity. 32, 187-199 (2010).</li><li>Treanor, B., Batista, F. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanistic+insight+into+lymphocyte+activation+through+quantitative+imaging+and+theoretical+modelling.">Mechanistic insight into lymphocyte activation through quantitative imaging and theoretical modelling.</a> Curr. Opin. Immunol. 19, 476-483 (2007).</li><li>Sylvain, N. R., Nguyen, K., Bunnell, S. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vav1-mediated+scaffolding+interactions+stabilize+SLP-76+microclusters+and+contribute+to+antigen-dependent+T+cell+responses.">Vav1-mediated scaffolding interactions stabilize SLP-76 microclusters and contribute to antigen-dependent T cell responses.</a> Sci. Signal. 4, ra14-ra14 (2011).</li><li>Purbhoo, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamics+of+subsynaptic+vesicles+and+surface+microclusters+at+the+immunological+synapse.">Dynamics of subsynaptic vesicles and surface microclusters at the immunological synapse.</a> Sci. Signal. 3, ra36-ra36 (2010).</li><li>Lasserre, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ezrin+tunes+T-cell+activation+by+controlling+Dlg1+and+microtubule+positioning+at+the+immunological+synapse.">Ezrin tunes T-cell activation by controlling Dlg1 and microtubule positioning at the immunological synapse.</a> EMBO. J. 29, 2301-2314 (2010).</li><li>Balagopalan, L., Sherman, E., Barr, V. A., Samelson, L. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imaging+techniques+for+assaying+lymphocyte+activation+in+action.">Imaging techniques for assaying lymphocyte activation in action.</a> Nat. Rev. Immunol. 11, 21-33 (2011).</li><li>Axelrod, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chapter+7:+Total+internal+reflection+fluorescence+microscopy.">Chapter 7: Total internal reflection fluorescence microscopy.</a> Methods Cell. Biol. 89, 169-221 (2008).</li><li>Williamson, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pre-existing+clusters+of+the+adaptor+Lat+do+not+participate+in+early+T+cell+signaling+events.">Pre-existing clusters of the adaptor Lat do not participate in early T cell signaling events.</a> Nat. Immunol. 12, 655-662 (2011).</li></ol>

Tous les animaux utilisés dans ces expériences ont été maintenues dans un agent pathogène spécifique sans l&#39;environnement, et les expériences ont été approuvés par le National Institutes of soins de la santé animale et le Comité utilisation.

Nous décrivons ici un système à étudier de signalisation spécifiques de l&#39;antigène dans les cellules primaires de souris en utilisant T TIRFM et bicouches lipidiques supportées en verre comme les APC artificielles. La technique repose sur l&#39;expression de protéines GFP succès marqués dans ces cellules. La transfection de cellules T est toujours une tâche difficile. En règle générale, la livraison ou l&#39;électroporation des gènes en utilisant des rétrovirus ou lentivirus sont utilisés. Une technique n&#39;est pas supérieure sur l&#39;autre, les deux ont leurs limites et leurs avantages. Nous constatons que l&#39;électroporation a les avantages suivants: 1) Il n&#39;est pas nécessaire que les cellules soient en division active, comme l&#39;exige pour les rétrovirus, mais pas les lentivirus, et 2) Le niveau d&#39;expression peut être contrôlée en faisant varier le temps les cellules sont incubées avant l&#39;imagerie. Le plus grand inconvénient est que l&#39;on trouve qu&#39;il est très difficile d&#39;exprimer des protéines qui sont de grande taille dans les cellules primaires. Nous avons présenté une méthode qui nous donne la viabilité des cellules très bonne après l&#39;électroporation. En conséquence, il est applicable à l&#39;utiliser pour atteindre gene silencing siRNA médiation. Nous décrivons également ici une mesure à deux canaux microscope TIRF simultanée d&#39;acquisition qui est chromatiquement corrigé et ne nécessite pas d&#39;alignement séparé pour différentes longueurs d&#39;onde. Ces capacités, mais sont disponibles dans le commerce. Notre système est basé sur les principes de microscopie TIRF publiées par des experts dans le domaine et est moins cher que les alternatives commerciales. Une critique possible de notre conception est que nous utilisons le même angle d&#39;incidence pour les longueurs d&#39;onde d&#39;excitation différentes. Cela se traduirait par une profondeur de pénétration différente pour la FRBR longueurs d&#39;onde d&#39;excitation différentes. Nous pensons que ces effets sont faibles, car l&#39;onde évanescente est un champ décroissance exponentielle et la profondeur du champ FRBR est une fonction linéaire de longueur d&#39;onde. Fluorophores proches de la surface de verre connaîtra aucune différence d&#39;intensité laser entre les deux longueurs d&#39;onde. Pour fluorophores près de la peprofondeur netration, la différence d&#39;intensité sera de 1,3 fois pour les deux longueurs d&#39;onde 488 nm et 640 et 1,15 fois pour les deux longueurs d&#39;onde 488 et 561 nm. Le même système peut être utilisé en conjonction avec des techniques de résolution de super qui font usage de l&#39;éclairage TIRF. Nous avons également décrit un système à deux caméra qui est intégrée personnalisée. Comme le système TIRF, appareils similaires sont également disponibles dans le commerce. Notre système offre une flexibilité de changer les filtres et dichroïques, permettant son utilisation avec différentes combinaisons de longueurs d&#39;onde. L&#39;inconvénient de notre système est le premier degré de rotation nécessaire pour aligner les deux images. Ce problème peut être résolu en utilisant la caméra peuplements qui sont parcourus et piézo offrent des degrés de rotation de l&#39;alignement. On a également mis en oeuvre avec succès un système à deux caméras sur ce microscope, dans lequel les caméras sont différents et ont des tailles de pixel différentes. Un tel système serait utile si on avait besoin de sensibilité dans un canal et une grande dyplage dynamique dans une autre, qui tous deux sont rarement disponibles dans le même appareil. Nous avons utilisé le Photometrics HQ-2 à huis clos à binning 2x2 qui nous donne une taille de pixels effectifs de 12,9 um avec l&#39;Photometrics Quant-EM caméra qui a une taille de pixel de 16 microns. A 180 mm de longueur focale de l&#39;objectif du tube a été utilisé pour la Quant-EM et un 145 mm de longueur focale de l&#39;objectif du tube a été utilisé pour l&#39;appareil photo HQ-2. Le HQ-2 a été contrôlé à l&#39;aide de logiciels et de la Metamorph Quant-EM a été contrôlé par micro-gestionnaire de logiciels sur un ordinateur séparé en mode de déclenchement externe. Le déclenchement externe a été fournie à la caméra Quant-EM en utilisant une sortie numérique de la carte DAC de mesure informatique, qui a été mis en œuvre un volet supplémentaire dans les réglages de l&#39;éclairage configure de Metamorph. Le rapport des longueurs focales des lentilles de tube correspond au rapport entre les tailles de pixel efficace. Un alignement représentant est montré dans la figure 5.

<table border="1"><tbody><tr><td> Nom du réactif </td><td> Entreprise </td><td> Numéro de catalogue </td><td> Commentaires </td></tr><tr><td> Amaxa Nucleofector Kit pour les cellules T de souris </td><td> Lonza Inc </td><td> APV-1006 </td><td></td></tr><tr><td> Purelink HiPure plasmide Midiprep Kit </td><td> Life Technologies </td><td> K2100-05 </td><td> Pour preps d&#39;ADN d&#39;endotoxines libres </td></tr><tr><td> Amaxa Nucleofector périphérique </td><td> Lonza Inc </td><td> AAD-1001 </td><td></td></tr><tr><td> Recombinant murin d&#39;IL-2 </td><td> Peprotech Inc </td><td> 212-12 </td><td></td></tr><tr><td> Fluoresbrite Multifluorescent microsphères 0.20μm </td><td> Polysciences, Inc </td><td> 24050-5 </td><td></td></tr><tr><td> Lab-Tek II 8-bien chambré lamelle </td><td> Thermo Scientific, Nunc </td><td> 155409 </td><td></td></tr></tbody></table>

a tirf microscopy technique for real-time, simultaneous imaging of the tcr and its associated signaling proteins

Signalisation est initiée à travers le récepteur de cellule T (TCR) lorsqu&#39;il est engagé par des fragments peptidiques antigéniques liés par Complexe Majeur d&#39;Histocompatibilité (pMHC) des protéines exprimées à la surface des cellules présentatrices d&#39;antigènes (APC). Le complexe TCR est composé de l&#39;hétérodimère de liaison du ligand TCRαβ qui associe de manière non covalente avec les dimères (CD3 εδ et εγ hétérodimères et l&#39;homodimère ζζ) 1. Lors de l&#39;engagement du récepteur, les chaînes CD3 Ç sont phosphorylées par la kinase de la famille Src, Lck. Cela conduit au recrutement de la famille Syk kinase, ZAP70, qui est ensuite phosphorylée et activée par Lck. Après cela, ZAP70 phosphoryle l&#39;adaptateur protéines LAT et SLP76, l&#39;ouverture de la formation du complexe de signalisation proximale contenant un grand nombre de molécules de signalisation différents 2. La formation de ce complexe entraîne par la suite en calcium et en Ras-dépendante traactivation du facteur nscription et l&#39;initiation par conséquent d&#39;une série complexe de programmes d&#39;expression génique qui donnent lieu à la différenciation des cellules T 2. Les signaux du TCR (et l&#39;état résultant de la différenciation) sont modulés par de nombreux autres facteurs, y compris la puissance d&#39;antigène et la diaphonie avec co-stimulatory/co-inhibitory, chimiokine, et les récepteurs de cytokines 3-4. L&#39;étude de l&#39;organisation spatiale et temporelle du complexe de signalisation dans des conditions de stimulation proximale divers est, par conséquent, essentiel pour comprendre la voie de signalisation du TCR, ainsi que sa régulation par d&#39;autres voies de signalisation. Un système modèle très utile pour étudier de signalisation initiée par le TCR à la membrane plasmique dans les cellules T est bicouches lipidiques de verre soutenus par, comme décrit précédemment 5-6. Ils peuvent être utilisés pour présenter des complexes antigéniques PMHC, l&#39;adhésion et de co-stimulation des molécules pour les cellules T-servant APC artificielles. Par imagerie des cellules T en interaction avec labicouche lipidique en utilisant la microscopie totale interne fluorescence à réflexion (TIRFM), nous pouvons restreindre l&#39;excitation à 100 nm au sein de l&#39;espace entre le verre et la surface de la cellule 7-8. Cela nous permet de l&#39;image surtout les événements de signalisation se produisant à la membrane plasmique. Comme nous nous intéressons à l&#39;imagerie du recrutement de protéines de signalisation au complexe TCR, nous décrivons une à deux caméras d&#39;imagerie TIRF système dans lequel le TCR, marqué par Fab fluorescente (fragment de liaison antigène) des fragments de l&#39;anticorps H57 (purifiée à partir d&#39;hybridomes H57-597 , ATCC, numéro ATCC: HB-218) qui est spécifique pour TCRβ, et les protéines de signalisation, marqué avec la GFP, peut être imagée et simultanément en temps réel. Cette stratégie est nécessaire en raison de la nature hautement dynamique à la fois des cellules T et des événements de signalisation qui se produisent à la TCR. Cette modalité d&#39;imagerie a permis aux chercheurs de ligands seule image 9-11 ainsi que le recrutement de molécules de signalisation des récepteurs activés etest un excellent système pour étudier la biochimie in situ 12-16.

Watch this Scientific Journal Video about A TIRF Microscopy Technique for Real-time, Simultaneous Imaging of the TCR and its Associated Signaling Proteins at JoVE.com

A TIRF Microscopy Technique for Real-time, Simultaneous Imaging of the TCR and its Associated Signaling Proteins

Le cloisonnement des protéines soit au sein de la membrane plasmique ou dans des endroits intracellulaires est un mécanisme de régulation qui peuvent grandement influencer les résultats de signalisation, d&#39;où, à comprendre la signalisation, il est important d&#39;étudier le comportement spatial et temporel des protéines impliquées. Nous décrivons ici un système de microscopie TIRF base pour étudier la transduction du signal dans les cellules T, mais est largement applicable.

Une technique de microscopie TIRF en temps réel, imagerie simultanée du TCR et de ses associés protéines de signalisation

Signaling is initiated through the T Cell Receptor (TCR) when it is engaged by antigenic peptide fragments bound by Major Histocompatibility Complex ...

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Research

JoVE Journal

Immunology and Infection

23.7K vues.  National Institute of Allergy and Infectious Diseases, National Institutes of Health. Le cloisonnement des protéines soit au sein de la membrane plasmique ou dans des endroits intracellulaires est un mécanisme de régulation qui peuvent grandement influencer les résultats de signalisation, d'où, à comprendre la signalisation, il est important d'étudier le comportement spatial et temporel des protéines impliquées. Nous décrivons ici un système de microscopie TIRF base pour étudier la transduction du signal dans les cellules T, mais est la...

Vidéo: A TIRF Microscopy Technique for Real-time, Simultaneous Imaging of the TCR and its Associated Signaling Proteins

Real-time Imaging of Leukotriene B4 Mediated Cell Migration and BLT1 Interactions with &beta;-arrestin

G-protein coupled receptors (GPCRs) belong to the seven transmembrane protein family and mediate the transduction of extracellular signals to intracellular responses. GPCRs control diverse biological functions such as chemotaxis, intracellular calcium release, gene regulation in a ligand dependent manner via heterotrimeric G-proteins1-2. Ligand binding induces a series of conformational changes leading to activation of heterotrimeric G-proteins that modulate levels of second messengers such as cyclic adenosine monophosphate (cAMP), inositol triphosphate (IP3) and diacyl glycerol (DG). Concomitant with activation of the receptor ligand binding also initiates a series of events to attenuate the receptor signaling via desensitization, sequestration and/or internalization. The desensitization process of GPCRs occurs via receptor phosphorylation by G-protein receptor kinases (GRKs) and subsequent binding of &beta;-arrestins3. &beta;-arrestins are cytosolic proteins and translocate to membrane upon GPCR activation, binding to phosphorylated receptors (most cases) there by facilitating receptor internalization 4-6.
Leukotriene B4 (LTB4) is a pro-inflammatory lipid molecule derived from arachidonic acid pathway and mediates its actions via GPCRs, LTB4 receptor 1 (BLT1; a high affinity receptor) and LTB4 receptor 2 (BLT2; a low affinity receptor)7-9. The LTB4-BLT1 pathway has been shown to be critical in several inflammatory diseases including, asthma, arthritis and atherosclerosis10-17. The current paper describes the methodologies developed to monitor LTB4-induced leukocyte migration and the interactions of BLT1 with &beta;-arrestin and , receptor translocation in live cells using microscopy imaging techniques18-19.
Bone marrow derived dendritic cells from C57BL/6 mice were isolated and cultured as previously described 20-21. These cells were tested in live cell imaging methods to demonstrate LTB4 induced cell migration. The human BLT1 was tagged with red fluorescent protein (BLT1-RFP) at C-terminus and &beta;-arrestin1 tagged with green fluorescent protein (&beta;-arr-GFP) and transfected the both plasmids into Rat Basophilic Leukomia (RBL-2H3) cell lines18-19. The kinetics of interaction between these proteins and localization were monitored using live cell video microscopy. The methodologies in the current paper describe the use of microscopic techniques to investigate the functional responses of G-protein coupled receptors in live cells. The current paper also describes the use of Metamorph software to quantify the fluorescence intensities to determine the kinetics of receptor and cytosolic protein interactions.

Real-time Imaging of Leukotriene B4 Mediated Cell Migration and BLT1 Interactions with &amp;#946;-arrestin

This paper describes the methodology to determine the chemotactic response of leukocytes to specific ligands and identify interactions between the cell surface receptors and cytosolic proteins using live cell imaging techniques.

Imagerie en temps réel des leucotriènes B 4</subMigration> Cell Mediated et BLT1 Interactions avec β-arrestine

G-protein coupled receptors (GPCRs) belong to the seven transmembrane protein family and mediate the transduction of extracellular signals to ...

Recherche

Immunologie et infection

Real-time Live Imaging of T-cell Signaling Complex Formation

Protection against infectious diseases is mediated by the immune system 1,2. T lymphocytes are the master coordinators of the immune system, regulating the activation and responses of multiple immune cells 3,4. T-cell activation is dependent on the recognition of specific antigens displayed by antigen presenting cells (APCs). The T-cell antigen receptor (TCR) is specific to each T-cell clone and determines antigen specificity 5. The binding of the TCR to the antigen induces the phosphorylation of components of the TCR complex. In order to promote T-cell activation, this signal must be transduced from the membrane to the cytoplasm and the nucleus, initiating various crucial responses such as recruitment of signaling proteins to the TCR;APC site (the immune synapse), their molecular activation, cytoskeletal rearrangement, elevation of intracellular calcium concentration, and changes in gene expression 6,7. The correct initiation and termination of activating signals is crucial for appropriate T-cell responses. The activity of signaling proteins is dependent on the formation and termination of protein-protein interactions, post translational modifications such as protein phosphorylation, formation of protein complexes, protein ubiquitylation and the recruitment of proteins to various cellular sites 8. Understanding the inner workings of the T-cell activation process is crucial for both immunological research and clinical applications.
Various assays have been developed in order to investigate protein-protein interactions; however, biochemical assays, such as the widely used co-immunoprecipitation method, do not allow protein location to be discerned, thus precluding the observation of valuable insights into the dynamics of cellular mechanisms. Additionally, these bulk assays usually combine proteins from many different cells that might be at different stages of the investigated cellular process. This can have a detrimental effect on temporal resolution. The use of real-time imaging of live cells allows both the spatial tracking of proteins and the ability to temporally distinguish between signaling events, thus shedding light on the dynamics of the process 9,10. We present a method of real-time imaging of signaling-complex formation during T-cell activation. Primary T-cells or T-cell lines, such as Jurkat, are transfected with plasmids encoding for proteins of interest fused to monomeric fluorescent proteins, preventing non-physiological oligomerization 11. Live T cells are dropped over a coverslip pre-coated with T-cell activating antibody 8,9, which binds to the CD3/TCR complex, inducing T-cell activation while overcoming the need for specific activating antigens. Activated cells are constantly imaged with the use of confocal microscopy. Imaging data are analyzed to yield quantitative results, such as the colocalization coefficient of the signaling proteins.

We describe a live-cell imaging method that provides insight into protein dynamics during the T-cell activation process. We demonstrate the combined usage of the T-cell spreading assay, confocal microscopy and imaging analysis to yield quantitative results to follow signaling complex formation throughout T-cell activation.

En temps réel l&#39;imagerie en direct de T-signalisation cellulaire Formation Complex

Protection against infectious diseases is mediated by the immune system 1,2. T lymphocytes are the master coordinators of the immune system, regulating ...

Real-time Imaging of Endothelial Cell-cell Junctions During Neutrophil Transmigration Under Physiological Flow

During inflammation, leukocytes leave the circulation and cross the endothelium to fight invading pathogens in underlying tissues. This process is known as leukocyte transendothelial migration. Two routes for leukocytes to cross the endothelial monolayer have been described: the paracellular route, i.e., through the cell-cell junctions and the transcellular route, i.e., through the endothelial cell body. However, it has been technically difficult to discriminate between the para- and transcellular route. We developed a simple in vitro assay to study the distribution of endogenous VE-cadherin and PECAM-1 during neutrophil transendothelial migration under physiological flow conditions. Prior to neutrophil perfusion, endothelial cells were briefly treated with fluorescently-labeled antibodies against VE-cadherin and PECAM-1. These antibodies did not interfere with the function of both proteins, as was determined by electrical cell-substrate impedance sensing and FRAP measurements. Using this assay, we were able to follow the distribution of endogenous VE-cadherin and PECAM-1 during transendothelial migration under flow conditions and discriminate between the para- and transcellular migration routes of the leukocytes across the endothelium.

Leukocytes cross the endothelial monolayer using the paracellular or the transcellular route. We developed a simple assay to follow the distribution of endogenous junctional VE-cadherin and PECAM-1 during leukocyte transendothelial migration under physiological flow to discriminate between the two transmigration routes.

Imagerie en temps réel des jonctions endothéliales cellule-cellule Pendant neutrophiles Transmigration Sous physiologique débit

During inflammation, leukocytes leave the circulation and cross the endothelium to fight invading pathogens in underlying tissues. This process is known ...

Real-time Imaging of Myeloid Cells Dynamics in ApcMin/+ Intestinal Tumors by Spinning Disk Confocal Microscopy

Myeloid cells are the most abundant immune cells within tumors and have been shown to promote tumor progression. Modern intravital imaging techniques enable the observation of live cellular behavior inside the organ but can be challenging in some types of cancer due to organ and tumor accessibility such as intestine. Direct observation of intestinal tumors has not been previously reported. A surgical procedure described here allows direct observation of myeloid cell dynamics within the intestinal tumors in live mice by using transgenic fluorescent reporter mice and injectable tracers or antibodies. For this purpose, a four-color, multi-region, micro-lensed spinning disk confocal microscope that allows long-term continuous imaging with rapid image acquisition has been used. ApcMin/+ mice that develop multiple adenomas in the small intestine are crossed with c-fms-EGFP mice to visualize myeloid cells and with ACTB-ECFP mice to visualize intestinal epithelial cells of the crypts. Procedures for labeling different tumor components, such as blood vessels and neutrophils, and the procedure for positioning the tumor for imaging through the serosal surface are also described. Time-lapse movies compiled from several hours of imaging allow the analysis of myeloid cell behavior in situ in the intestinal microenvironment.

Real-time Imaging of Myeloid Cells Dynamics in ApcMin/+ Intestinal Tumors by Spinning Disk Confocal Microscopy

By using transgenic reporter mice and injectable fluorescent labels, long-term intravital spinning disk confocal microscopy enables direct visualization of myeloid cell behavior into intestinal adenoma in the ApcMin/+ colorectal cancer model.

Imagerie en temps réel des cellules myéloïdes Dynamique<em&gt; Apc<sup&gt; Min / +</sup</em&gt; Intestinale tumeurs par Spinning Disk microscopie confocale

Myeloid cells are the most abundant immune cells within tumors and have been shown to promote tumor progression. Modern intravital imaging techniques ...

Simultaneous Quantification of T-Cell Receptor Excision Circles (TRECs) and K-Deleting Recombination Excision Circles (KRECs) by Real-time PCR

T-cell receptor excision circles (TRECs) and K-deleting recombination excision circles (KRECs) are circularized DNA elements formed during recombination process that creates T- and B-cell receptors. Because TRECs and KRECs are unable to replicate, they are diluted after each cell division, and therefore persist in the cell. Their quantity in peripheral blood can be considered as an estimation of thymic and bone marrow output. By combining well established and commonly used TREC assay with a modified version of KREC assay, we have developed a duplex quantitative real-time PCR that allows quantification of both newly-produced T and B lymphocytes in a single assay. The number of TRECs and KRECs are obtained using a standard curve prepared by serially diluting TREC and KREC signal joints cloned in a bacterial plasmid, together with a fragment of T-cell receptor alpha constant gene that serves as reference gene. Results are reported as number of TRECs and KRECs/106 cells or per ml of blood. The quantification of these DNA fragments have been proven useful for monitoring immune reconstitution following bone marrow transplantation in both children and adults, for improved characterization of immune deficiencies, or for better understanding of certain immunomodulating drug activity.

Simultaneous Quantification of T-Cell Receptor Excision Circles TRECs and K-Deleting Recombination Excision Circles KRECs by Real-time PCR

Here, we describe a method for simultaneous quantification of T-cell receptor excision circles (TRECs) and K-deleting recombination excision circles (KRECs). The TREC/KREC assay can be used as marker of thymic and bone marrow output.

Quantification simultanée de T-Cell Receptor Cercles excision (TREC) et cercles K-Suppression recombinaison Excision (KRECs) par PCR en temps réel

T-cell receptor excision circles (TRECs) and K-deleting recombination excision circles (KRECs) are circularized DNA elements formed during recombination ...

Analysis of Yersinia enterocolitica Effector Translocation into Host Cells Using Beta-lactamase Effector Fusions

Many gram-negative bacteria including pathogenic Yersinia spp. employ type III secretion systems to translocate effector proteins into eukaryotic target cells. Inside the host cell the effector proteins manipulate cellular functions to the benefit of the bacteria. To better understand the control of type III secretion during host cell interaction, sensitive and accurate assays to measure translocation are required. We here describe the application of an assay based on the fusion of a Yersinia enterocolitica effector protein fragment (Yersinia outer protein; YopE) with TEM-1 beta-lactamase for quantitative analysis of translocation. The assay relies on cleavage of a cell permeant FRET dye (CCF4/AM) by translocated beta-lactamase fusion. After cleavage of the cephalosporin core of CCF4 by the beta-lactamase, FRET from coumarin to fluorescein is disrupted and excitation of the coumarin moiety leads to blue fluorescence emission. Different applications of this method have been described in the literature highlighting its versatility. The method allows for analysis of translocation in vitro and also in in vivo, e.g., in a mouse model. Detection of the fluorescence signals can be performed using plate readers, FACS analysis or fluorescence microscopy. In the setup described here, in vitro translocation of effector fusions into HeLa cells by different Yersinia mutants is monitored by laser scanning microscopy. Recording intracellular conversion of the FRET reporter by the beta-lactamase effector fusion in real-time provides robust quantitative results. We here show exemplary data, demonstrating increased translocation by a Y. enterocolitica YopE mutant compared to the wild type strain.

Analysis of Yersinia enterocolitica Effector Translocation into Host Cells Using Beta-lactamase Effector Fusions

Effector translocation into host cells via a type III secretion system is a common virulence strategy among gram-negative bacteria. A beta-lactamase effector fusion based assay for quantitative analysis of translocation was applied. In Yersinia infected cells, conversion of a FRET reporter by the beta-lactamase is monitored using laser scanning microscopy.

Analyse de<em&gt; Yersinia enterocolitica</em&gt; Effecteur translocation dans les cellules hôtes à l&#39;aide de bêta-lactamase effecteur Fusions

Many gram-negative bacteria including pathogenic Yersinia spp. employ type III secretion systems to translocate effector proteins into eukaryotic target ...

Imaging Neutrophils and Monocytes in Mesenteric Veins by Intravital Microscopy on Anaesthetized Mice in Real Time

Efficient immune response is dependent on rapid mobilization of blood leukocytes to the site of infection or injury. Investigating leukocyte migration in vivo is crucial for understanding the molecular basis of leukocyte transendothelial migration and interaction with vascular endothelium. One powerful approach involves intravital microscopy on transgenic mice expressing fluorescent proteins in cells of interest.
Here we present a protocol for imaging monocytes and neutrophils in the CX3CR1gfp/wt mouse i.v. injected with orange dye-labeled neutrophils with an inverted confocal microscope. Time-lapse movies gathered from 30 min&#160;to several hours of imaging allow the analysis of leukocyte behavior in mesenteric veins under both steady state and inflammatory conditions. We also describe the steps to locally induce blood vessel inflammation with TLR2/TLR1 agonist Pam3SK4 and monitor the subsequent recruitment of neutrophils and monocytes.
The presented technique can also be used to monitor other populations of leukocytes and investigate molecules implicated in leukocyte recruitment or trafficking using other stimuli or transgenic mice.

We detail a protocol to monitor the behavior of neutrophils and monocytes in mesenteric veins under steady state and inflammatory conditions using intravital confocal microscopy on anaesthetized mice.

Imagerie neutrophiles et des monocytes dans les veines mésentérique par Microscopie intravitale sur des souris anesthésiées en temps réel

Efficient immune response is dependent on rapid mobilization of blood leukocytes to the site of infection or injury. Investigating leukocyte migration in ...

Purification of Viral DNA for the Identification of Associated Viral and Cellular Proteins

The goal of this protocol is to isolate herpes simplex virus type 1 (HSV-1) DNA from infected cells for the identification of associated viral and cellular proteins by mass spectrometry. Although proteins that interact with viral genomes play major roles in determining the outcome of infection, a comprehensive analysis of viral genome associated proteins was not previously feasible. Here we demonstrate a method that enables the direct purification of HSV-1 genomes from infected cells. Replicating viral DNA is selectively labeled with modified nucleotides that contain an alkyne functional group. Labeled DNA is then specifically and irreversibly tagged via the covalent attachment of biotin azide via a copper(I)-catalyzed azide-alkyne cycloaddition or click reaction. Biotin-tagged DNA is purified on streptavidin-coated beads and associated proteins are eluted and identified by mass spectrometry. This method enables the selective targeting and isolation of HSV-1 replication forks or whole genomes from complex biological environments. Furthermore, adaptation of this approach will allow for the investigation of various aspects of herpesviral infection, as well as the examination of the genomes of other DNA viruses.

The goal of this protocol is to specifically tag and selectively isolate viral DNA from infected cells for the characterization of viral genome associated proteins.

Purification de l’ADN Viral pour l’Identification des protéines virus et cellulaires associées

The goal of this protocol is to isolate herpes simplex virus type 1 (HSV-1) DNA from infected cells for the identification of associated viral and ...

Real-time Imaging and Quantification of Fungal Biofilm Development Using a Two-Phase Recirculating Flow System

In oropharyngeal candidiasis, members of the genus Candida must adhere to and grow on the oral mucosal surface while under the effects of salivary flow. While models for the growth under flow have been developed, many of these systems are expensive, or do not allow imaging while the cells are under flow. We have developed a novel apparatus that allows us to image the growth and development of Candida albicans cells under flow and in real-time. Here, we detail the protocol for the assembly and use of this flow apparatus, as well as the quantification of data that are generated. We are able to quantify the rates that the cells attach to and detach from the slide, as well as to determine a measure of the biomass on the slide over time. This system is both economical and versatile, working with many types of light microscopes, including inexpensive benchtop microscopes, and is capable of extended imaging times compared to other flow systems. Overall, this is a low-throughput system that can provide highly detailed real-time information on the biofilm growth of fungal species under flow.

We describe the assembly, operation, and cleaning of a flow apparatus designed to image fungal biofilm formation in real time while under flow. We also provide and discuss quantitative algorithms to be used on the acquired images.

Imagerie en temps réel et la Quantification du développement de biofilms fongiques en utilisant un système de flux de recirculation en deux phases

In oropharyngeal candidiasis, members of the genus Candida must adhere to and grow on the oral mucosal surface while under the effects of salivary flow. ...

Image Processing Protocol for the Analysis of the Diffusion and Cluster Size of Membrane Receptors by Fluorescence Microscopy

Particle tracking on a video sequence and the posterior analysis of their trajectories is nowadays a common operation in many biological studies. Using the analysis of cell membrane receptor clusters as a model, we present a detailed protocol for this image analysis task using Fiji (ImageJ) and Matlab routines to: 1) define regions of interest and design masks adapted to these regions; 2) track the particles in fluorescence microscopy videos; 3) analyze the diffusion and intensity characteristics of selected tracks. The quantitative analysis of the diffusion coefficients, types of motion, and cluster size obtained by fluorescence microscopy and image processing provides a valuable tool to objectively determine particle dynamics and the consequences of modifying environmental conditions. In this article we present detailed protocols for the analysis of these features. The method described here not only allows single-molecule tracking detection, but also automates the estimation of lateral diffusion parameters at the cell membrane, classifies the type of trajectory and allows complete analysis thus overcoming the difficulties in quantifying spot size over its entire trajectory at the cell membrane.

Here, we present a protocol for single particle tracking image analysis that allows quantitative evaluation of diffusion coefficients, types of motion and cluster sizes of single particles detected by fluorescence microscopy.

Traitement d’image protocole pour l’analyse de la Diffusion et la taille de Cluster de récepteurs membranaires par microscopie de Fluorescence

Particle tracking on a video sequence and the posterior analysis of their trajectories is nowadays a common operation in many biological studies. Using ...