We thank Dr. Shahid Mukhtar for critiquing the manuscript and Dr. Xinnian Dong for the sample data analysis file. This work is supported by a NSF-CAREER award (IOS-1350244) to KPM and the UAB Biology Department.

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Mit abnehmender verfügbaren Ackerland und wachsende Bevölkerung, sind die Forscher auf der ganzen Welt mit der dringendsten Bedürfnisse für die Verbesserung von Kulturpflanzen in Frage gestellt. Die Ausbeute kann stark durch verschiedene biotische und abiotische Stressfaktoren beeinflusst werden. Unter ihnen ist Pathogeninfektion eine der führenden Ursachen für Ernteertragsreduktion, für ca. 12% Verluste allein in den USA 45 verantwortlich. Um dieses Problem zu beheben, hat massive Forschung im Modell ...

Aufgrund ihrer sessilen Natur werden Pflanzen ständig von einer Vielzahl von Krankheitserregern, die verschiedene Lebensweisen und Ernährungsstrategien 1 bedroht. In erster Näherung, biotrophen Erreger behalten ihre Gastgeber, am Leben zu Nährstoffen abzurufen, während nekrotrophe Krankheitserreger aktiv geheime Giftstoffe und Enzyme, um Wirtsgewebe töten und ernähren sich von den toten Zellen 1. Eine weitere Gruppe von Krankheitserregern, bezeichnet hemibiotrophs beginnt ihre Infektion natürlich mit der biotrophen Bühne und verschiebt sich nach nekrotrophe Stufe bei Erreichen einer bestimmten Schwelle von pathogenen Ansammlung 2. Um sich gegen diese Mikroorganismen wirksam zu verteidigen, haben Pflanzen einen komplizierten angeborenen Immunsystems mit mehreren Überwachungsmechanismen ausgestattet, um den Erreger Angriff zu erkennen und auslösen entwickelt lokalisiert programmierten Zelltod 3 sowie Systemische Akquirierte Resistenz (SAR) 4. Die aktuelle Forschung auf die Charakterisierung der wesentlichen sig konzentriertnaling Komponenten und Quer Gespräche innerhalb der Anlage Immunsystem 5. Wie in der &quot;Zig-Zag&quot; Modell 5 vorgeschlagen, die erste Schicht der Anlage angeborenen Immunantwort erfordert die Anwesenheit von Plasmamembran lokalisierte pattern recognition receptors (PRR), um die Invasion einer Mikrobe zu erkennen. PRRs können Microbe-associated molecular patterns (mAmps) zu erkennen und zu etablieren MAMP-Triggered Immunity (MTI) 6. Neben Induktion eines Transkriptions-Hochregulierung von Genen antimikrobielle PR-Proteinen 7 kodiert, führt MTI auf eine Vielzahl von Ereignissen, die das Wachstum des Pathogens, einschließlich der Produktion von reaktiven Sauerstoffspezies (ROS) und reaktive Stickstoffspezies (RNS), Abscheiden Callose an die Zellwand zu verhaften sowie die Aktivierung von mehreren Kinase Signalwege 8. Bis jetzt wurden mehrere MAMPS identifiziert MTI in Arabidopsis auslösen, einschließlich bakterieller flg22 9 </sup&gt; (Ein 22 Aminosäurefragment von Flagellin abgeleitet) elf18 10 (18 Aminosäuren aus dem bakteriellen Elongationsfaktor Tu Übersetzung) und einem strukturellen Zellwandkomponente Peptidoglykane 11. Um eine erfolgreiche Infektion zu etablieren, haben einige spezielle Krankheitserreger die Möglichkeit, geheime Virulenz Effektor-Proteine ​​in die intrazelluläre oder interzellulären Räumen entwickelt und damit zu unter MTI und lösen Effektor-Triggered Anfälligkeit (ETS) 12,13. Zum Beispiel können die Virulenz Effektoren Mitogen-aktivierte Proteinkinase (MAPK) Phosphorylierungskaskaden MTI zu inaktivieren, um die Entwicklung der Erkrankung in dem infizierten Gewebe 14-16 induzieren. Während der dynamischen Koevolution zwischen Hosts und Krankheitserreger, Pflanzen entwickelte auch die Gegenstrategie, die Effektor-Proteine ​​erkennen und dämpfen das Pathogen Virulenz Moleküle 17. Diese direkte oder indirekte Effektor Erkennung durch Krankheitsresistenz (R) 18-Proteine ​​vermittelt wird. Meiste tSaum sind Mitglieder der NB-LRR (Nukleotid-Bindungs ​​und Leucin-reichen Wiederholungen) Familie 19. Die Wahrnehmung eines avirulenten Effektorzellen durch ein R-Protein löst eine stärkere und breitere Immunantwort charakterisiert als Effektor-Triggered Immunity (ETI) 20. Neben der Induktion der Expression von Abwehrgene 21 und die Produktion von Verteidigungsmetaboliten 22, ETI führt oft zu einer raschen lokalisierten programmierten Zelltod als hypersensible Reaktion (HR) bekannt, die Pathogen-Ausbreitung in das benachbarte Gewebe 3 zu beschränken. Neben der lokalisierten programmierten Zelltods 23, sind Pflanzen der Lage, eine langfristige und systemweiten Immunantwort bezeichnet Systemische Akquirierte Resistenz (SAR) 4. Bei Provokation mit einem biotrophe Erreger, Pflanzenzellen auszulösen, die Biosynthese und Akkumulation eines endogenen Phytohormon Salicylsäure (SA) und PR-Proteinen sowohl in lokalen und systemischen Geweben 24. Durch tsein Verfahren ein gesteigertes Zustand der Bereitschaft in den nicht-infizierten Blättern, die für die Montage schneller Abwehrreaktionen bei einer nachfolgenden Infektion durch ein breites Spektrum von Erregern 24 ermöglicht erreicht. SA und ihre synthetischen Analoga, wie Benzo (1,2,3) thiadiazol-7-thiocarbonsäure-S-methyl ester (BTH) und 2,6-Dichlorisonicotinsäure (INA) in der Lage sind, chemisch zu induzieren Salicylsäure (SA) -Triggered Immunity (STI) bei der externen Anwendung 24. Nonexpressor der Pathogenese-Assoziierte Gene 1 (NPR1) wird vorgeschlagen, einer der SA-Rezeptoren und wirkt als Haupttranskriptionsregulator während SA-vermittelte Abwehrreaktion sowohl in lokalen und systemischen Geweben 21,25,26 sein. Es hat sich eindeutig gezeigt, dass NPR1 für SAR Einrichtung erforderlich ist, und der Verlust von NPR1 führt zu dramatischen Anfälligkeit gegenüber Pseudomonas syringae 25. Um umfassend charakterisieren die molekularen Beitrag der PflanzenKomponenten in den Pflanzen-Pathogen-Interaktionen, mehrere Biotests wurden entwickelt, um spezifische Abwehr Veranstaltungen zu messen, einschließlich ROS Burst 27, Kallose-Abscheidung 28, Verteidigung Gene Expression und Anhäufung von ihrer Proteinprodukte 21. Während diese Einzeltests können Einblicke in eine spezifische Form der Pflanze Immunantwort bereitzustellen, keiner von ihnen ist jedoch in der Lage sind, das komplette Abwehrreaktion an der gesamten Pflanze Ebene darstellen. Umgekehrt ist die Quantifizierung der Pathogen Wachstum nach der Infektion bietet eine Gesamtschätzung der Immunantwort auf der organismischen Ebene. Daher ist die Entwicklung und Optimierung von einem präzisen und hoch standardisierte Erreger Inokulation Assay kritischen Kraftstoff den Forschungen und Entdeckungen auf den Arabidopsis Immunantworten. Pseudomonas syringae, ein Gram-negatives Bakterium, wurde als Phytopathogen Lage verursacht Krankheit in einem Bereich von Wirten, einschließlich Pflanzen Arabidops identifiziertenist 29. Als Modellpflanze-Pathogen-System, das Arabidopsis - P. syringae Interaktion wurde in großem Umfang angewendet, um die molekularen Mechanismen zugrunde liegenden Pflanzenabwehrreaktionen 29 zu verstehen. Bisher über 50 P. syringae Pathovare wurden basierend auf ihrer Fähigkeit, verschiedene Pflanzenarten infizieren 30 identifizierten . P. syringae pv. tomato DC3000 (Pst DC3000) 31 und P. syringae pv. maculicola ES4326 (PSM ES4326) 32 sind die beiden am weitesten verbreitete und umfassend charakterisiert virulenten Stämmen. Abgesehen davon, dass durch die Pflanze erkannt und Auslösen des MTI Reaktion Pst DC3000 und PSM ES4326 sind zur Sekretion virulenten Effektorproteine ​​MTI drücken und lösen ETS, das Wachstum des Pathogens 31,33 begünstigen. Funktionell sezieren die Interaktion zwischen Arabidopsis und P. syringae, multiple0; Pathogeninfektion Methoden wurden auf der Grundlage des Erregers Liefer Ansatz entwickelt. Für Bodenkultur Pflanzen, können Krankheitserreger mit einer Spritze Infiltration, Vakuuminfiltration, Tauch Inokulation und Sprühinokulation 29,34 geliefert werden. Vor kurzem wurde Sämling Flut Inokulation Assay entwickelt, um große Bildschirme auf Gewebekulturplatten durchführen wachsenen jungen Arabidopsis-Pflanzen 35. Syringe Infiltration, als einer der am häufigsten verwendeten Ansatz, manuell liefert die Erreger in den Apoplasten durch die natürlichen Blattöffnungen bezeichnet Spaltöffnungen 29. Durch diesen Ansatz, gleiche Mengen von P. syringae in die befallenen Blatt infiltriert werden und die Stärke der pflanzlichen Immunantwort ist umgekehrt an die das Wachstum des Pathogens Niveaus korreliert. Daher dient die Quantifizierung der Pathogen Wachstum als eine optimale Vorgehensweise, um die Immunfunktion im gesamten Werksebene zu bewerten. Darüber hinaus können Spritzen Infiltration der lokalen und systemischen Gewebe zu unterscheiden, worin B kanne in der Charakterisierung der molekularen Mechanismen SAR 36 erhoben. In dem folgenden Protokoll beschreiben wir eine optimierte Spritze Infiltration Assay mit Psm ES4326 um Arabidopsis-Mutanten für erhöhte Krankheitsanfälligkeit (EDS) zu screenen. Dieses Protokoll wird zwei Arabidopsis-Genotypen zu beschäftigen: ein Wildtyp-Ökotyp Columbia-0 (Col-0), Pflanzen (Kontrolle) und npr1-1 loss-of-function-Mutanten (hypersusceptible) das wird mit virulenten Bakterienstamm Psm ES4326 37 infiziert werden. Die npr1-1 Mutante trägt eine Punktmutation in der Ankyrin-Repeat-Consensussequenz des NPR1 Molekül, das die hoch konservierten Histidin zu Tyrosin verändert und macht das Protein nicht-funktionellen 25. Darüber hinaus ist eine Anzahl von Modifikationen der Spritze Infiltration Assay beschrieben, die die Quantifizierung von Fehlern in den spezifischen Schichten aus Immunantwort, einschließlich MTI und STI ermöglichen.

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bacterial leaf infiltration assay for fine characterization of plant defense responses using the arabidopsis thaliana-pseudomonas syringae pathosystem

In Abwesenheit von spezialisierten mobilen Immunzellen, Pflanzen nutzen ihre lokalisierten programmierten Zelltod und Systemische Akquirierte Resistenz, sich gegen Pathogenbefall verteidigen. Der Beitrag einer speziellen Arabidopsis Gens an der Gesamtanlage Immunantwort spezifisch und quantitativ durch Bestimmung des Wachstum des Pathogens im infizierten Gewebe bewertet. Seit über drei Jahrzehnten, die hemibiotrophe Bakterium Pseudomonas syringae pv. Maculicola ES4326 (PSM ES4326) wurde weithin als Modell Erreger, die molekularen Mechanismen der Arabidopsis Immunantwort zugrunde liegenden Untersuchung angewendet. Um Krankheitserreger in das Blattgewebe zu liefern, haben mehrfache Impfung Verfahren festgelegt, beispielsweise Spritzen Infiltration, dip Inokulation, Spray, Vakuuminfiltration, und Hochwasser Inokulation. Das folgende Protokoll beschreibt eine optimierte Spritze Infiltrationsverfahren zu virulenten Psm ES4326 in Blätter von erwachsenen liefernBodenkultur Arabidopsis-Pflanzen und genau Bildschirm für erhöhte Krankheitsanfälligkeit (EDS) gegenüber diesem Erreger. Zusätzlich kann dieses Protokoll mit mehreren Vorbehandlungen, ergänzt werden, um spezifische Immundefekten weiter zerlegen innerhalb unterschiedlicher Schichten des pflanzlichen Abwehr einschließlich Salicylsäure (SA) -Triggered Immunity (STI) und MAMP-Triggered Immunity (MTI).

Das Protokoll beschreiben wir hier stellt eine optimierte P. syringae Spritze Infiltration Assay eine quantitative Bewertung der Immunantwort in Arabidopsis-Pflanzen. Wie in Figur 1 dargestellt ist, ist die Spritze Infiltration Psm ES4326 von Pathogen-Extraktion und Quantifizierung über serielle Verdünnungen und Kolonien Aufzählung folgt. Wie in Schritt 3 im Protokolltext beschrieben, kann Verbesserte Krankheitsanfälligkeit (EDS) gegen Psm<...

Watch this Scientific Journal Video about Bacterial Leaf Infiltration Assay for Fine Characterization of Plant Defense Responses using the Arabidopsis thaliana-Pseudomonas syringae Pathosystem at JoVE

Bacterial Leaf Infiltration Assay for Fine Characterization of Plant Defense Responses using the Arabidopsis thaliana-Pseudomonas syringae Pathosystem | Immunology and Infection | Video

Bacterial Leaf Infiltration Assay for Fine Characterization of Plant Defense Responses using the Arabidopsis thaliana-Pseudomonas syringae Pathosystem

Quantification of pathogen growth is a powerful tool to characterize various Arabidopsis thaliana (hereafter: Arabidopsis) immune responses. The method described here presents an optimized syringe infiltration assay to quantify the Pseudomonas syringae pv. maculicola ES4326 growth in adult Arabidopsis leaves.

Bakterielle Blatt Infiltration Assay für Bildende Charakterisierung pflanzlicher Abwehrreaktionen mit Hilfe der<em&gt; Arabidopsis thaliana-Pseudomonas syringae</em&gt; Pathosystem

In the absence of specialized mobile immune cells, plants utilize their localized programmed cell death and Systemic Acquired Resistance to defend ...

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Bacterial Leaf Infiltration Assay for Fine Characterization of Plant Defense Responses using the Arabidopsis thaliana-Pseudomonas syringae Pathosystem

Plant Biology

Plant Responses to the Environment

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21.5K Aufrufe.  University of Alabama at Birmingham. Quantification of pathogen growth is a powerful tool to characterize various Arabidopsis thaliana (hereafter: Arabidopsis) immune responses. The method described here presents an optimized syringe infiltration assay to quantify the Pseudomonas syringae pv. maculicola ES4326 growth in adult Arabidopsis leaves.

Serie: Bacterial Leaf Infiltration Assay for Fine Characterization of Plant Defense Responses using the Arabidopsis thaliana-Pseudomonas syringae Pathosystem

Assay for Pathogen-Associated Molecular Pattern (PAMP)-Triggered Immunity (PTI) in Plants

To perceive potential pathogens in their environment, plants use pattern recognition receptors (PRRs) present on their plasma membranes. PRRs recognize conserved microbial features called pathogen-associated molecular patterns (PAMPs) and this detection leads to PAMP-triggered immunity (PTI), which effectively prevents colonization of plant tissues by non-pathogens1,2. The most well studied system in PTI is the FLS2-dependent pathway3. FLS2 recognizes the PAMP flg22 that is a component of bacterial flagellin. 
Successful pathogens possess virulence factors or effectors that can suppress PTI and allow the pathogen to cause disease1. Some plants in turn possess resistance genes that detect effectors or their activity, which leads to effector-triggered immunity (ETI)2.
We describe a cell death-based assay for PTI modified from Oh and Collmer4. The assay was standardized in N. benthamiana, which is being used increasingly as a model system for the study of plant-pathogen interactions5. PTI is induced by infiltration of a non-pathogenic bacterial strain into leaves. Seven hours later, a bacterial strain that either causes disease or which activates ETI is infiltrated into an area overlapping the original infiltration zone. PTI induced by the first infiltration is able to delay or prevent the appearance of cell death due to the second challenge infiltration. Conversely, the appearance of cell death in the overlapping area of inoculation indicates a breakdown of PTI. 
Four different combinations of inducers of PTI and challenge inoculations were standardized (Table 1). The assay was tested on non-silenced N. benthamiana plants that served as the control and plants silenced for FLS2 that were predicted to be compromised in their ability to develop PTI.

Assay for Pathogen-Associated Molecular Pattern PAMP-Triggered Immunity PTI in Plants

A cell death-based assay for PTI in Nicotiana benthamiana plants is described.

Assay für Pathogen-Associated Molecular Pattern (PAMP)-Triggered Immunity (PTI) in Pflanzen

To perceive potential pathogens in their environment, plants use pattern recognition receptors (PRRs) present on their plasma membranes. PRRs recognize ...

Forschung

Immunologie und Infektion

Assessing Stomatal Response to Live Bacterial Cells using Whole Leaf Imaging

Stomata are natural openings in the plant epidermis responsible for gas exchange between plant interior and environment. They are formed by a pair of guard cells, which are able to close the stomatal pore in response to a number of external factors including light intensity, carbon dioxide concentration, and relative humidity (RH). The stomatal pore is also the main route for pathogen entry into leaves, a crucial step for disease development. Recent studies have unveiled that closure of the pore is effective in minimizing bacterial disease development in Arabidopsis plants; an integral part of plant innate immunity. Previously, we have used epidermal peels to assess stomatal response to live bacteria (Melotto et al. 2006); however maintaining favorable environmental conditions for both plant epidermal peels and bacterial cells has been challenging. Leaf epidermis can be kept alive and healthy with MES buffer (10 mM KCl, 25 mM MES-KOH, pH 6.15) for electrophysiological experiments of guard cells. However, this buffer is not appropriate for obtaining bacterial suspension. On the other hand, bacterial cells can be kept alive in water which is not proper to maintain epidermal peels for long period of times. When an epidermal peel floats on water, the cells in the peel that are exposed to air dry within 4 hours limiting the timing to conduct the experiment. An ideal method for assessing the effect of a particular stimulus on guard cells should present minimal interference to stomatal physiology and to the natural environment of the plant as much as possible. We, therefore, developed a new method to assess stomatal response to live bacteria in which leaf wounding and manipulation is greatly minimized aiming to provide an easily reproducible and reliable stomatal assay. The protocol is based on staining of intact leaf with propidium iodide (PI), incubation of staining leaf with bacterial suspension, and observation of leaves under laser scanning confocal microscope. Finally, this method allows for the observation of the same live leaf sample over extended periods of time using conditions that closely mimic the natural conditions under which plants are attacked by pathogens.

We have developed a simple and reproducible protocol to access stomatal response to live bacteria. This method minimizes wounding and manipulation of the leaf as compared to the use of epidermal peels reported previously.

Die Beurteilung stomatäre Response to Bakterienzellen Live mit Whole Leaf Imaging

Stomata are natural openings in the plant epidermis responsible for gas exchange between plant interior and environment. They are formed by a pair of ...

Microwave Assisted Rapid Diagnosis of Plant Virus Diseases by Transmission Electron Microscopy

Investigations of ultrastructural changes induced by viruses are often necessary to clearly identify viral diseases in plants. With conventional sample preparation for transmission electron microscopy (TEM) such investigations can take several days1,2 and are therefore not suited for a rapid diagnosis of plant virus diseases. Microwave fixation can be used to drastically reduce sample preparation time for TEM investigations with similar ultrastructural results as observed after conventionally sample preparation3-5. Many different custom made microwave devices are currently available which can be used for the successful fixation and embedding of biological samples for TEM investigations5-8. In this study we demonstrate on Tobacco Mosaic Virus (TMV) infected Nicotiana tabacum plants that it is possible to diagnose ultrastructural alterations in leaves in about half a day by using microwave assisted sample preparation for TEM. We have chosen to perform this study with a commercially available microwave device as it performs sample preparation almost fully automatically5 in contrast to the other available devices where many steps still have to be performed manually6-8 and are therefore more time and labor consuming. As sample preparation is performed fully automatically negative staining of viral particles in the sap of the remaining TMV-infected leaves and the following examination of ultrastructure and size can be performed during fixation and embedding.

This study describes a method that allows the rapid and clear diagnosis of plant virus diseases in about half a day by using a combination of microwave assisted plant sample preparation for transmission electron microscopy and negative staining methods.

Mikrowelle Assisted Schnelle Diagnose von Plant Virus Erkrankungen durch Transmission Electron Microscopy

Investigations of ultrastructural changes induced by viruses are often necessary to clearly identify viral diseases in plants. With conventional sample ...

Measuring Bacterial Load and Immune Responses in Mice Infected with Listeria monocytogenes

Listeria monocytogenes (Listeria) is a Gram-positive facultative intracellular pathogen1. Mouse studies typically employ intravenous injection of Listeria, which results in systemic infection2. After injection, Listeria quickly disseminates to the spleen and liver due to uptake by CD8&alpha;+ dendritic cells and Kupffer cells3,4. Once phagocytosed, various bacterial proteins enable Listeria to escape the phagosome, survive within the cytosol, and infect neighboring cells5. During the first three days of infection, different innate immune cells (e.g. monocytes, neutrophils, NK cells, dendritic cells) mediate bactericidal mechanisms that minimize Listeria proliferation. CD8+ T cells are subsequently recruited and responsible for the eventual clearance of Listeria from the host, typically within 10 days of infection6.
Successful clearance of Listeria from infected mice depends on the appropriate onset of host immune responses6	. There is a broad range of sensitivities amongst inbred mouse strains7,8. Generally, mice with increased susceptibility to Listeria infection are less able to control bacterial proliferation, demonstrating increased bacterial load and/or delayed clearance compared to resistant mice. Genetic studies, including linkage analyses and knockout mouse strains, have identified various genes for which sequence variation affects host responses to Listeria infection6,8-14. Determination and comparison of infection kinetics between different mouse strains is therefore an important method for identifying host genetic factors that contribute to immune responses against Listeria. Comparison of host responses to different Listeria strains is also an effective way to identify bacterial virulence factors that may serve as potential targets for antibiotic therapy or vaccine design.
We describe here a straightforward method for measuring bacterial load (colony forming units [CFU] per tissue) and preparing single-cell suspensions of the liver and spleen for FACS analysis of immune responses in Listeria-infected mice. This method is particularly useful for initial characterization of Listeria infection in novel mouse strains, as well as comparison of immune responses between different mouse strains infected with Listeria. We use the Listeria monocytogenes EGD strain15 that, when cultured on blood agar, exhibits a characteristic halo zone around each colony due to &beta;-hemolysis1 (Figure 1). Bacterial load and immune responses can be determined at any time-point after infection by culturing tissue homogenate on blood agar plates and preparing tissue cell suspensions for FACS analysis using the protocols described below. We would note that individuals who are immunocompromised or pregnant should not handle Listeria, and the relevant institutional biosafety committee and animal facility management should be consulted before work commences.

Measuring Bacterial Load and Immune Responses in Mice Infected with Listeria monocytogenes

Listeria monocytogenes is a model organism for studying immune responses and genetic susceptibility to intracellular bacteria in mice. This method enables one to measure bacterial load and generate single-cell suspensions of the liver and spleen from mice for FACS analysis to determine changes in immune cells due to Listeria infection.

Mess-bakterielle Belastung und Immunreaktionen in Mäuse Infizierte mit Listeria monocytogenes</em

Listeria monocytogenes (Listeria) is a Gram-positive facultative intracellular pathogen1. Mouse studies typically employ intravenous injection of ...

Visualization of Bacterial Toxin Induced Responses Using Live Cell Fluorescence Microscopy

Bacterial toxins bind to cholesterol in membranes, forming pores that allow for leakage of cellular contents and influx of materials from the external environment. The cell can either recover from this insult, which requires active membrane repair processes, or else die depending on the amount of toxin exposure and cell type1. In addition, these toxins induce strong inflammatory responses in infected hosts through activation of immune cells, including macrophages, which produce an array of pro-inflammatory cytokines2. Many Gram positive bacteria produce cholesterol binding toxins which have been shown to contribute to their virulence through largely uncharacterized mechanisms.
Morphologic changes in the plasma membrane of cells exposed to these toxins include their sequestration into cholesterol-enriched surface protrusions, which can be shed into the extracellular space, suggesting an intrinsic cellular defense mechanism3,4. This process occurs on all cells in the absence of metabolic activity, and can be visualized using EM after chemical fixation4. In immune cells such as macrophages that mediate inflammation in response to toxin exposure, induced membrane vesicles are suggested to contain cytokines of the IL-1 family and may be responsible both for shedding toxin and disseminating these pro-inflammatory cytokines5,6,7. A link between IL-1&beta; release and a specific type of cell death, termed pyroptosis has been suggested, as both are caspase-1 dependent processes8. To sort out the complexities of this macrophage response, which includes toxin binding, shedding of membrane vesicles, cytokine release, and potentially cell death, we have developed labeling techniques and fluorescence microscopy methods that allow for real time visualization of toxin-cell interactions, including measurements of dysfunction and death (Figure 1). Use of live cell imaging is necessary due to limitations in other techniques. Biochemical approaches cannot resolve effects occurring in individual cells, while flow cytometry does not offer high resolution, real-time visualization of individual cells. The methods described here can be applied to kinetic analysis of responses induced by other stimuli involving complex phenotypic changes in cells.

Methods for purifying the cholesterol binding toxin streptolysin O from recombinant E. coli and visualization of toxin binding to live eukaryotic cells are described. Localized delivery of toxin induces rapid and complex changes in targeted cells revealing novel aspects of toxin biology.

Visualisierung der bakteriellen Toxin induzierten Reaktionen mit Live Cell Fluoreszenzmikroskopie

Bacterial toxins bind to cholesterol in membranes, forming pores that allow for leakage of cellular contents and influx of materials from the external ...

Systemic Bacterial Infection and Immune Defense Phenotypes in Drosophila Melanogaster

The fruit fly Drosophila melanogaster is one of the premier model organisms for studying the function and evolution of immune defense. Many aspects of innate immunity are conserved between insects and mammals, and since Drosophila can readily be genetically and experimentally manipulated, they are powerful for studying immune system function and the physiological consequences of disease. The procedure demonstrated here allows infection of flies by introduction of bacteria directly into the body cavity, bypassing epithelial barriers and more passive forms of defense and allowing focus on systemic infection. The procedure includes protocols for the measuring rates of host mortality, systemic pathogen load, and degree of induction of the host immune system. This infection procedure is inexpensive, robust and quantitatively repeatable, and can be used in studies of functional genetics, evolutionary life history, and physiology.

Systemic Bacterial Infection and Immune Defense Phenotypes in Drosophila Melanogaster

Drosophila melanogaster is an outstanding model organism for studying innate immune systems and the physiological consequences of infection and disease. This protocol describes how to deliver robust and quantitatively repeatable bacterial infections to D. melanogaster, and how to subsequently measure infection severity and quantify the host immune response.

Systemische bakterielle Infektion und Immunabwehr Phänotypen in<em&gt; Drosophila melanogaster</em

The fruit fly Drosophila melanogaster is one of the premier model organisms for studying the function and evolution of immune defense. Many aspects of ...

Application of Long-term cultured Interferon-&#947; Enzyme-linked Immunospot Assay for Assessing Effector and Memory T Cell Responses in Cattle

Effector and memory T cells are generated through developmental programing of na&#239;ve cells following antigen recognition. If the infection is controlled up to 95 % of the T cells generated during the expansion phase are eliminated (i.e., contraction phase) and memory T cells remain, sometimes for a lifetime. In humans, two functionally distinct subsets of memory T cells have been described based on the expression of lymph node homing receptors. Central memory T cells express C-C chemokine receptor 7 and CD45RO and are mainly located in T-cell areas of secondary lymphoid organs. Effector memory T cells express CD45RO, lack CCR7 and display receptors associated with lymphocyte homing to peripheral or inflamed tissues. Effector T cells do not express either CCR7 or CD45RO but upon encounter with antigen produce effector cytokines, such as interferon-&#947;. Interferon-&#947; release assays are used for the diagnosis of bovine and human tuberculosis and detect primarily effector and effector memory T cell responses. Central memory T cell responses by CD4+ T cells to vaccination, on the other hand, may be used to predict vaccine efficacy, as demonstrated with simian immunodeficiency virus infection of non-human primates, tuberculosis in mice, and malaria in humans. Several studies with mice and humans as well as unpublished data on cattle, have demonstrated that interferon-&#947; ELISPOT assays measure central memory T cell responses. With this assay, peripheral blood mononuclear cells are cultured in decreasing concentration of antigen for 10 to 14 days (long-term culture), allowing effector responses to peak and wane; facilitating central memory T cells to differentiate and expand within the culture.

Application of Long-term cultured Interferon-&amp;#947; Enzyme-linked Immunospot Assay for Assessing Effector and Memory T Cell Responses in Cattle

Long-term cultured interferon-&#947; enzyme-linked immunospot assay is used as a measure of central memory responses and correlates with protective anti-mycobacterial vaccine responses. With this assay, peripheral blood mononuclear cells are stimulated with mycobacterial antigens and interleukin-2 for 14 days, enabling differentiation and expansion of central memory T cells.

Anwendung von Langzeit kultiviert Interferon-γ Enzyme-linked Immunospot Assay zur Beurteilung Effektor und Gedächtnis-T-Zell-Antworten in Cattle

Effector and memory T cells are generated through developmental programing of na&#239;ve cells following antigen recognition. If the infection is ...

Characterization of Thymus-dependent and Thymus-independent Immunoglobulin Isotype Responses in Mice Using Enzyme-linked Immunosorbent Assay

Antibodies, also termed as immunoglobulins (Ig), secreted by differentiated B lymphocytes, plasmablasts/plasma cells, in humoral immunity provide a formidable defense against invading pathogens via diverse mechanisms. One major goal of vaccination is to induce protective antigen-specific antibodies to prevent life-threatening infections. Both thymus-dependent (TD) and thymus-independent (TI) antigens can elicit robust antigen-specific IgM responses and can also induce the production of isotype-switched antibodies (IgG, IgA and IgE) as well as the generation of memory B cells with the help provided by antigen presenting cells (APCs). Here, we describe a protocol to characterize TD and TI Ig isotype responses in mice using enzyme-linked immunosorbent assay (ELISA). In this protocol, TD and TI Ig responses are elicited in mice by intraperitoneal (i.p.) immunization with hapten-conjugated model antigens TNP-KLH (in alum) and TNP-polysaccharide (in PBS), respectively. To induce TD memory response, a booster immunization of TNP-KLH in alum is given at 3 weeks after the first immunization with the same antigen/adjuvant. Mouse sera are harvested at different time points before and after immunization. Total serum Ig levels and TNP-specific antibodies are subsequently quantified using Ig isotype-specific Sandwich and indirect ELISA, respectively. In order to correctly quantify the serum concentration of each Ig isotype, the samples need to be appropriately diluted to fit within the linear range of the standard curves. Using this protocol, we have consistently obtained reliable results with high specificity and sensitivity. When used in combination with other complementary methods such as flow cytometry, in vitro culture of splenic B cells and immunohistochemical staining (IHC), this protocol will allow researchers to gain a comprehensive understanding of antibody responses in a given experimental setting.

In this paper, we describe a protocol to characterize T-dependent and T-independent immunoglobulin (Ig) isotype responses in mice using ELISA. This method used alone or in combination with flow cytometry will allow researchers to identify differences in B cell-mediated Ig isotype responses in mice following T-dependent and T-independent antigen immunization.

Charakterisierung der Thymus-abhängig und Thymus-unabhängige Immunglobulin Isotype Antworten bei Mäusen mit Enzym-linked Immunosorbentprobe Assay

Antibodies, also termed as immunoglobulins (Ig), secreted by differentiated B lymphocytes, plasmablasts/plasma cells, in humoral immunity provide a ...

Using a Bacterial Pathogen to Probe for Cellular and Organismic-level Host Responses

There are a variety of strategies bacterial pathogens employ to survive and proliferate once inside the eukaryotic cell. The so-called 'cytosolic' pathogens (Listeria monocytogenes, Shigella flexneri, Burkholderia pseudomallei, Francisella tularensis, and Rickettsia spp.) gain access to the infected cell cytosol by physically and enzymatically degrading the primary vacuolar membrane. Once in the cytosol, these pathogens both proliferate as well as generate sufficient mechanical forces to penetrate the plasma membrane of the host cell in order to infect new cells. Here, we show how this terminal step of the cellular infection cycle of L. monocytogenes (Lm) can be quantified by both colony-forming unit assays and flow cytometry and give examples of how both pathogen- and host-encoded factors impact this process. We also show a close correspondence of Lm infection dynamics of cultured cells infected in vitro and those of hepatic cells derived from mice infected in vivo. These function-based assays are relatively simple and can be readily scaled up for discovery-based high-throughput screens for modulators of eukaryotic cell function.

We describe both in vitro and in vivo infection assays that can be used to analyze the activities of host-encoding factors.

Verwenden eine bakterielle Erreger, Sonde für zelluläre und organismische Ebene Host Antworten

There are a variety of strategies bacterial pathogens employ to survive and proliferate once inside the eukaryotic cell. The so-called 'cytosolic' ...

Opsonophagocytic Killing Assay to Assess Immunological Responses Against Bacterial Pathogens

A key aspect of the immune response to bacterial colonization of the host is phagocytosis. An opsonophagocytic killing assay (OPKA) is an experimental procedure in which phagocytic cells are co-cultured with bacterial units. The immune cells will phagocytose and kill the bacterial cultures in a complement-dependent manner. The efficiency of the immune-mediated cell killing is dependent on a number of factors and can be used to determine how different bacterial cultures compare with regard to resistance to cell death. In this way, the efficacy of potential immune-based therapeutics can be assessed against specific bacterial strains and/or serotypes. In this protocol, we describe a simplified OPKA that utilizes basic culture conditions and cell counting to determine bacterial cell viability after co-culture with treatment conditions and HL-60 immune cells. This method has been successfully utilized with a number of different pneumococcal serotypes, capsular and acapsular strains, and other bacterial species. The advantages of this OPKA protocol are its simplicity, versatility (as this assay is not limited to antibody treatments as opsonins), and minimization of time and reagents to assess basic experimental groups.

This opsonophagocytic killing assay is used to compare the ability of phagocytic immune cells to respond to and kill bacteria based on different treatments and/or conditions. Classically, this assay serves as the gold&#160;standard for assessing effector functions of antibodies raised against a bacterium as opsonin.

Opsonophagocytic Tötung Assay Immunreaktionen gegen bakterielle Krankheitserreger zu bewerten

A key aspect of the immune response to bacterial colonization of the host is phagocytosis. An opsonophagocytic killing assay (OPKA) is an experimental ...