Name: visualization of macrophage lytic cell death during mycobacterial infection in zebrafish embryos via intravital microscopy
Uploaded: 2019-01-09T15:00:00
Description: Watch this Scientific Journal Video about Visualization of Macrophage Lytic Cell Death During Mycobacterial Infection in Zebrafish Embryos via Intravital Microscopy at JoVE.com

We thank Dr. Zilong Wen for sharing zebrafish strains, Dr. Stefan Oehlers and Dr. David Tobin for sharing M. marinum related resources, Yuepeng He for assistance in figure preparation. This work was supported by the National Natural Science Foundation of China (81801977) (B.Y.), the Outstanding Youth Training Program of Shanghai Municipal Health Commission (2018YQ54) (B.Y.), Shanghai Sailing Program (18YF1420400) (B.Y.), and Open Fund of Shanghai Key Laboratory of Tuberculosis (2018KF02) (B.Y.).

Zebrafish were raised under standard conditions in compliance with laboratory animal guidelines for ethical review of animal welfare (GB/T 35823-2018). All zebrafish experiments in this study were approved (2019-A016-01) and conducted at Shanghai Public Health Clinical Center, Fudan University.
1. M. marinum Single Cell Inoculum Preparation (Figure 1)
<ol>
	<li>Thaw Cerulean-fluorescent M. marinum glycerol stock from -80 &#176;C and inoculate a...

<ol>
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This protocol describes the visualization of macrophage death during mycobacterial infection. Based on factors such as the integrity of the cell membrane, infection driven cell death can be divided into apoptosis and lytic cell death24,25. Lytic cell death is more stressful for the organism than apoptosis, because it triggers a strong inflammatory response 24,25. Observation of lytic cell death in vivo is...

Mycobacterial infection has been demonstrated to cause host immune cell death1. For example, an attenuated strain will trigger apoptosis in macrophages and contain the infection. However, a virulent strain will trigger lytic cell death, causing bacterial dissemination1,2. Considering the impact these different types of cell death have on host anti-mycobacterial response, a detailed observation of macrophage cell death during mycobacterial infection in vivo is needed.
The conventional methods for measuring cell death are to use dead cell stains, such as Annnexin V, TUNEL, or acridine orange/propidium iodide staining3,4,5. However, these methods are unable to shed light on the dynamic process of cell death in vivo. The observation of cell death in vitro has already been facilitated by live imaging6. However, whether the results accurately mimic physiological conditions remains unclear.
Zebrafish have been an excellent model for studying host anti-mycobacterium responses. It has a highly conserved immune system similar to that of humans, an easily manipulated genome, and the early embryos are transparent, which allows for live imaging7,8,9. After infection with M. marinum, adult zebrafish form typical mature granuloma structures, and embryonic zebrafish form early granuloma like structures9,10. The dynamic process of innate immune cell-bacteria interaction has been explored previously in the zebrafish M. marinum infection model11,12. However, due to high spatial-temporal resolution requirement, the details surrounding the death of the innate immune cells remain largely undefined.
Here we describe how to visualize the process of macrophage lytic cell death triggered by mycobacterial infection in vivo. This protocol may also be applied to visualizing cellular behavior in vivo during development and inflammation.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>0.05% Tween-80</td>
			<td>Sigma</td>
			<td>P1379</td>
			<td></td>
		</tr>
		<tr>
			<td>10 mL syringe</td>
			<td>Solarbio</td>
			<td>YA0552</td>
			<td></td>
		</tr>
		<tr>
			<td>10% OADC</td>
			<td>BD</td>
			<td>211886</td>
			<td></td>
		</tr>
		<tr>
			<td>3-aminobenzoic acid</td>
			<td>Sigma</td>
			<td>E10521</td>
			<td></td>
		</tr>
		<tr>
			<td>5 &#956;m filter</td>
			<td>Mille X</td>
			<td>SLSV025LS</td>
			<td></td>
		</tr>
		<tr>
			<td>50 &#956;l/ml hygromycin</td>
			<td>Sangon Biotech</td>
			<td>A600230</td>
			<td></td>
		</tr>
		<tr>
			<td>7H10</td>
			<td>BD</td>
			<td>262710</td>
			<td></td>
		</tr>
		<tr>
			<td>7H9</td>
			<td>BD</td>
			<td>262310</td>
			<td></td>
		</tr>
		<tr>
			<td>A glass bottom 35 mm dish</td>
			<td>In Vitro Scientific</td>
			<td>D35-10-0-N</td>
			<td></td>
		</tr>
		<tr>
			<td>Agarose</td>
			<td>Sangon Biotech</td>
			<td>A60015</td>
			<td></td>
		</tr>
		<tr>
			<td>Confocal microscope</td>
			<td>Leica</td>
			<td>TCS SP5 II</td>
			<td></td>
		</tr>
		<tr>
			<td>Enviromental Chamber</td>
			<td>Pecon</td>
			<td>temp control 37-2 digital</td>
			<td></td>
		</tr>
		<tr>
			<td>Eppendorf microloader</td>
			<td>Eppendorf</td>
			<td>No.5242956003</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass microscope slide</td>
			<td>Bioland Scientific LLC</td>
			<td>7105P</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycerol</td>
			<td>Sangon Biotech</td>
			<td>A100854</td>
			<td></td>
		</tr>
		<tr>
			<td>Incubator</td>
			<td>Keelrein</td>
			<td>PH-140(A)</td>
			<td></td>
		</tr>
		<tr>
			<td>M.marinum</td>
			<td></td>
			<td></td>
			<td>ATCC BAA-535</td>
		</tr>
		<tr>
			<td>Microinjection needle</td>
			<td>World Precision Instruments</td>
			<td>IB100F-4</td>
			<td></td>
		</tr>
		<tr>
			<td>Microinjector</td>
			<td>Eppendorf</td>
			<td>Femtojet</td>
			<td></td>
		</tr>
		<tr>
			<td>Micromanipulator</td>
			<td>NARISHIGE</td>
			<td>MN-151</td>
			<td></td>
		</tr>
		<tr>
			<td>msp12:cerulean</td>
			<td></td>
			<td></td>
			<td>Ref.: PMID 25470057; 27760340</td>
		</tr>
		<tr>
			<td>Phenol red</td>
			<td>Sigma</td>
			<td>P3532</td>
			<td></td>
		</tr>
		<tr>
			<td>PTU</td>
			<td>Sigma</td>
			<td>P7629</td>
			<td></td>
		</tr>
		<tr>
			<td>Single concavity glass microscope slide</td>
			<td>Sail Brand</td>
			<td>7103</td>
			<td></td>
		</tr>
		<tr>
			<td>Sonicator</td>
			<td>SCICNTZ</td>
			<td>JY92-IIDN</td>
			<td></td>
		</tr>
		<tr>
			<td>Spectrophotometer (OD600)</td>
			<td>Eppendorf AG</td>
			<td>22331 Hamburg</td>
			<td></td>
		</tr>
		<tr>
			<td>Stereo Microscope</td>
			<td>OLYMPUS</td>
			<td>SZX10</td>
			<td></td>
		</tr>
		<tr>
			<td>Tg(mfap4:eGFP)</td>
			<td></td>
			<td></td>
			<td>Ref.: PMID 30742890</td>
		</tr>
		<tr>
			<td>Tg(coro1a:eGFP;lyzDsRed2)</td>
			<td></td>
			<td></td>
			<td>Ref.: PMID 31278008</td>
		</tr>
		<tr>
			<td>Tg(mpeg1:LRLG;lyz:eGFP)</td>
			<td></td>
			<td></td>
			<td>Ref.: PMID 27424497; 17477879</td>
		</tr>
	</tbody>
</table>

visualization of macrophage lytic cell death during mycobacterial infection in zebrafish embryos via intravital microscopy

Zebrafish is an excellent model organism for studying innate immune cell behavior due to its transparent nature and reliance solely on its innate immune system during early development. The Zebrafish Mycobacterium marinum (M. marinum) infection model has been well-established in studying host immune response against mycobacterial infection. It has been suggested that different macrophage cell death types will lead to the diverse outcomes of mycobacterial infection. Here we describe a protocol using intravital microscopy to observe macrophage cell death in zebrafish embryos following M. marinum infection. Zebrafish transgenic lines that specifically label macrophages and neutrophils are infected via intramuscular microinjection of fluorescently labeled M. marinum in either the midbrain or the trunk. Infected zebrafish embryos are subsequently mounted on low melting agarose and observed by confocal microscopy in X-Y-Z-T dimensions. Because long-term live imaging requires using low laser power to avoid photobleaching and phototoxicity, a strongly expressing transgenic is highly recommended. This protocol facilitates the visualization of the dynamic processes in vivo, including immune cell migration, host pathogen interaction, and cell death.

Mycobacterium infection can trigger different host responses based on the routes of infection. In this protocol, zebrafish embryos are infected by intramuscular microinjection of fluorescently labeled bacteria into the midbrain or trunk (Figure 3) and observed by confocal live imaging. Infection via these two routes will locally restrict the infection causing innate immune cell recruitment and subsequent cell death.
Visualizing the details of innate immune cell de...

Watch this Scientific Journal Video about Visualization of Macrophage Lytic Cell Death During Mycobacterial Infection in Zebrafish Embryos via Intravital Microscopy at JoVE.com

Visualization of Macrophage Lytic Cell Death During Mycobacterial Infection in Zebrafish Embryos via Intravital Microscopy

This protocol describes a technique for visualizing macrophage behavior and death in embryonic zebrafish during Mycobacterium marinum infection. Steps for the preparation of bacteria, infection of the embryos, and intravital microscopy are included. This technique may be applied to the observation of cellular behavior and death in similar scenarios involving infection or sterile inflammation.

Zebrafish is an excellent model organism for studying innate immune cell behavior due to its transparent nature and reliance solely on its innate immune ...

This protocol can clearly differentiate macrophage cell death modes during mycobacterial infection. By observing multiple embryos in parallel, it greatly increases the probability of capturing the entire macrophage lytic cell death process. This protocol may also be applied to the observation of cell death and other cellular behavior in similar scenarios involving infection or sterile inflammation.During the extended live imaging, it is very important to keep the intensity of the laser as low as possible to avoid photobleaching and toxicity. After inoculation according to the manuscript, centrifuge the culture at 3000 times G for 10 minutes to collect the Mycobacterium marinum as a pellet. Discard all but 300 microliters of the supernatant, and re-suspend the pellet.Add three milliliters of 7H9 medium with 10%glycerol to further re-suspend the pellet, and then sonicate the suspension in a water bath at 100 watts, with 15 seconds on and 15 seconds off, for a total of two minutes to achieve a single cell homogenate. Transfer the bacterial suspension to a 10 milliliter syringe, and pass through a five micron filter to remove any bacterial clumps. Using a spectrophotometer, measure the optical density of the suspension, and dilute it with 7H9 media containing 10%glycerol to OD 600 at one.Divide the suspension into 10 microliter aliquots, and store at negative 80 degrees Celsius freezer for further use. First, heat the agarose in a 95 degree Celsius heating block until it is completely melted. Maintain the agarose in liquid form by placing it in a 45 degrees Celsius heating block.To mount for intramuscular infection in the trunk region, create the bottom agarose layer by pouring 0.5 milliliters of 1%weight by volume agarose evenly onto a glass slide. Place the slide on an icebox or cold surface for three minutes to solidify. After anesthetizing the zebrafish embryos, place up to 60 zebrafish embryos on the bottom agarose layer, and lay them out carefully in two rows.Remove any remaining water on the bottom agarose layer with tissue paper, before adding 0.3 milliliters of 0.5%weight by volume agarose to create the upper layer. Ensure that the embryos are completely embedded in the agarose. Return the glass slide to the icebox again to solidify the agarose.Keep the top layer of the agarose moist by covering the surface with extra E3 egg water. Next, adjust the microinjector and micromanipulator to the proper position and setting for microinjection. Transfer three microliters of prepared bacterial culture into the prepared needle using a microloader.Pipette slowly and carefully to avoid forming air bubbles. Inject 100 CFU into the trunk region. After microinjection, carefully flush the zebra fish embryos into fresh egg water with a plastic pipette.To mount for the midbrain infection, use a plastic pipette to transfer the four to six tricaine-anesthetized embryos into the agarose. Position the head of each embryo upwards carefully with a 10-gauge needle. Once all embryos positions are fixed, transfer the glass slide to an icebox or cold surface to let the agarose solidify.Inject 500 CFU into the midbrain. After microinjection, carefully flush the zebrafish embryos into fresh egg water with a plastic pipette. Once the agarose has completely solidified, cover the agarose with a layer of egg water.After setting up the environmental chamber, place the 35 millimeter glass bottom dish with the zebrafish in the environmental chamber. Open the 405 diode, argon at 20%power, and DPSS 561 nanometer laser. Set up the appropriate laser power in spectrum settings.Choose the XYZ sequential scan acquisition mode, and set images format to 512 by 512 pixels. Switch to live data mode, target the position of the first zebrafish, and mark the begin and end Z position. Repeat this process for each of the remaining embryos.Add a pause at the end of the program. Define the loop and cycle of the program, and save the file. In this study, we utilized previously reported transgenic coro1a:eGFP;lyzDsRed2, and transgenic mpeg1loxP;DsRed:loxPeGFP;lyz:eGFP, to distinguish the macrophages and the neutrophils in vivo.A macrophage heavily engorged with bacteria became round and displayed reduced motility, with eventual cytoplasmic swelling, rupturing of the cell membrane, and quick dissemination of the cytoplasmic content. UV-irradiated macrophages showed typical apoptotic cell phenotypes such as cell shrinkage, nuclear fragmentation, and chromatin condensation. It was also observed the macrophages actively phagocytosed and disseminated M.merinum.However, neutrophils had limited phagocytic capability, and quickly underwent lytic cell death without obvious bacterial engorgement. Combined with powerful gene editing tools, this protocol can provide an effective platform for further understanding the effect of a variety of factors on host-pathogen interaction in vivo.

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Immunology and Infection

Intravital Microscopy of the Inguinal Lymph Node

Lymph nodes (LN's), located throughout the body, are an integral component of the immune system. They serve as a site for induction of adaptive immune response and therefore, the development of effector cells. As such, LNs are key to fighting invading pathogens and maintaining health. The choice of LN to study is dictated by accessibility and the desired model; the inguinal lymph node is well situated and easily supports studies of biologically relevant models of skin and genital mucosal infection.
The inguinal LN, like all LNs, has an extensive microvascular network supplying it with blood. In general, this microvascular network includes the main feed arteriole of the LN that subsequently branches and feeds high endothelial venules (HEVs). HEVs are specialized for facilitating the trafficking of immune cells into the LN during both homeostasis and infection. How HEVs regulate trafficking into the LN under both of these circumstances is an area of intense exploration. The LN feed arteriole, has direct upstream influence on the HEVs and is the main supply of nutrients and cell rich blood into the LN. Furthermore, changes in the feed arteriole are implicated in facilitating induction of adaptive immune response. The LN microvasculature has obvious importance in maintaining an optimal blood supply to the LN and regulating immune cell influx into the LN, which are crucial elements in proper LN function and subsequently immune response. 
The ability to study the LN microvasculature in vivo is key to elucidating how the immune system and the microvasculature interact and influence one another within the LN. Here, we present a method for in vivo imaging of the inguinal lymph node. We focus on imaging of the microvasculature of the LN, paying particular attention to methods that ensure the study of healthy vessels, the ability to maintain imaging of viable vessels over a number of hours, and quantification of vessel magnitude. Methods for perfusion of the microvasculature with vasoactive drugs as well as the potential to trace and quantify cellular traffic are also presented. 
Intravital microscopy of the inguinal LN allows direct evaluation of microvascular functionality and real-time interface of the direct interface between immune cells, the LN, and the microcirculation. This technique potential to be combined with many immunological techniques and fluorescent cell labelling as well as manipulated to study vasculature of other LNs.

A technique for performing intravital microscopy of the inguinal lymph node (LN) is outlined. Such technique allows for real-time, in vivo study of the lymph node microvasculature and structure both during homeostasis and infection. This technique can be adapted to cell trafficking studies and to other lymph node sites.

Lymph nodes (LN's), located throughout the body, are an integral component of the immune system. They serve as a site for induction of adaptive immune ...

Infection of Zebrafish Embryos with Intracellular Bacterial Pathogens

Zebrafish (Danio rerio) embryos are increasingly used as a model for studying the function of the vertebrate innate immune system in host-pathogen interactions 1. The major cell types of the innate immune system, macrophages and neutrophils, develop during the first days of embryogenesis prior to the maturation of lymphocytes that are required for adaptive immune responses. The ease of obtaining large numbers of embryos, their accessibility due to external development, the optical transparency of embryonic and larval stages, a wide range of genetic tools, extensive mutant resources and collections of transgenic reporter lines, all add to the versatility of the zebrafish model. Salmonella enterica serovar Typhimurium (S. typhimurium) and Mycobacterium marinum can reside intracellularly in macrophages and are frequently used to study host-pathogen interactions in zebrafish embryos. The infection processes of these two bacterial pathogens are interesting to compare because S. typhimurium infection is acute and lethal within one day, whereas M. marinum infection is chronic and can be imaged up to the larval stage 2, 3. The site of micro-injection of bacteria into the embryo (Figure 1) determines whether the infection will rapidly become systemic or will initially remain localized. A rapid systemic infection can be established by micro-injecting bacteria directly into the blood circulation via the caudal vein at the posterior blood island or via the Duct of Cuvier, a wide circulation channel on the yolk sac connecting the heart to the trunk vasculature. At 1 dpf, when embryos at this stage have phagocytically active macrophages but neutrophils have not yet matured, injecting into the blood island is preferred. For injections at 2-3 dpf, when embryos also have developed functional (myeloperoxidase-producing) neutrophils, the Duct of Cuvier is preferred as the injection site. To study directed migration of myeloid cells towards local infections, bacteria can be injected into the tail muscle, otic vesicle, or hindbrain ventricle 4-6. In addition, the notochord, a structure that appears to be normally inaccessible to myeloid cells, is highly susceptible to local infection 7. A useful alternative for high-throughput applications is the injection of bacteria into the yolk of embryos within the first hours after fertilization 8. Combining fluorescent bacteria and transgenic zebrafish lines with fluorescent macrophages or neutrophils creates ideal circumstances for multi-color imaging of host-pathogen interactions. This video article will describe detailed protocols for intravenous and local infection of zebrafish embryos with S. typhimurium or M. marinum bacteria and for subsequent fluorescence imaging of the interaction with cells of the innate immune system.

Transparent zebrafish embryos have proved useful model hosts to visualize and functionally study interactions between innate immune cells and intracellular bacterial pathogens, such as Salmonella typhimurium and Mycobacterium marinum. Micro-injection of bacteria and multi-color fluorescence imaging are essential techniques involved in the application of zebrafish embryo infection models.

Zebrafish (Danio rerio) embryos are increasingly used as a model for studying the function of the vertebrate innate immune system in host-pathogen ...

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.

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

Highly Resolved Intravital Striped-illumination Microscopy of Germinal Centers

Monitoring cellular communication by intravital deep-tissue multi-photon microscopy is the key for understanding the fate of immune cells within thick tissue samples and organs in health and disease. By controlling the scanning pattern in multi-photon microscopy and applying appropriate numerical algorithms, we developed a striped-illumination approach, which enabled us to achieve 3-fold better axial resolution and improved signal-to-noise ratio, i.e. contrast, in more than 100 &#181;m tissue depth within highly scattering tissue of lymphoid organs as compared to standard multi-photon microscopy. The acquisition speed as well as photobleaching and photodamage effects were similar to standard photo-multiplier-based technique, whereas the imaging depth was slightly lower due to the use of field detectors. By using the striped-illumination approach, we are able to observe the dynamics of immune complex deposits on secondary follicular dendritic cells &#8211; on the level of a few protein molecules in germinal centers.

High-resolution intravital imaging with enhanced contrast up to 120 &#181;m depth in lymph nodes of adult mice is achieved by spatially modulating the excitation pattern of a multi-focal two-photon microscope. In 100 &#181;m depth we measured resolutions of 487 nm (lateral) and 551 nm (axial), thus circumventing scattering and diffraction limits.

Monitoring cellular communication by intravital deep-tissue multi-photon microscopy is the key for understanding the fate of immune cells within thick ...

Study of Phagolysosome Biogenesis in Live Macrophages

Phagocytic cells play a major role in the innate immune system by removing and eliminating invading microorganisms in their phagosomes. Phagosome maturation is the complex and tightly regulated process during which a nascent phagosome undergoes drastic transformation through well-orchestrated interactions with various cellular organelles and compartments in the cytoplasm. This process, which is essential for the physiological function of phagocytic cells by endowing phagosomes with their lytic and bactericidal properties, culminates in fusion of phagosomes with lysosomes and biogenesis of phagolysosomes which is considered to be the last and critical stage of maturation for phagosomes. In this report, we describe a live cell imaging based method for qualitative and quantitative analysis of the dynamic process of lysosome to phagosome content delivery, which is a hallmark of phagolysosome biogenesis. This approach uses IgG-coated microbeads as a model for phagocytosis and fluorophore-conjugated dextran molecules as a luminal lysosomal cargo probe, in order to follow the dynamic delivery of lysosmal content to the phagosomes in real time in live macrophages using time-lapse imaging and confocal laser scanning microscopy. Here we describe in detail the background, the preparation steps and the step-by-step experimental setup to enable easy and precise deployment of this method in other labs. Our described method is simple, robust, and most importantly, can be easily adapted to study phagosomal interactions and maturation in different systems and under various experimental settings such as use of various phagocytic cells types, loss-of-function experiments, different probes, and phagocytic particles.

Phagocytic cells play a major role in the innate immune system by removing and eliminating invading microorganisms in their phagosomes. Phagosome ...

Visualizing Non-lytic Exocytosis of Cryptococcus neoformans from Macrophages Using Digital Light Microscopy

Many aspects of the infection of macrophages by Cryptococcus neoformans have been extensively studied and well defined. However, one particular interaction that is not clearly understood is non-lytic exocytosis. In this process, yeast cells are released into the extracellular space by a poorly understood mechanism that leaves both the macrophage and Cn viable. Here, we describe how to follow a large number of individually infected macrophages for a 24 hr infection period by time-lapsed microscopy. Infected macrophages are housed in a heating chamber with a CO2 atmosphere attached to a microscope that provides the same conditions as a cell-culture incubator. Live digital microscopy can provide information about the dynamic interactions between a host and pathogen that is not available from static images. Being able to visualize each infected cell can provide clues as to how macrophages handle fungal infections, and vice versa. This technique is a powerful tool in studying the dynamics that are behind a complex phenomenon.

Visualizing Non-lytic Exocytosis of Cryptococcus neoformans from Macrophages Using Digital Light Microscopy

We describe how to visualize macrophage-C. neoformans (Cn) interactions in real time, with specific emphasis on the process of non-lytic exocytosis using digital light microscopy. Using this technique individually infected macrophages can be studied to ascertain various aspects of this phenomenon.

Many aspects of the infection of macrophages by Cryptococcus neoformans have been extensively studied and well defined. However, one particular ...

Intravital Microscopy Imaging of the Liver following Leishmania Infection: An Assessment of Hepatic Hemodynamics

Intravital microscopy (IVM) is a powerful optical imaging technique that has made possible the visualization, monitoring and quantification of various biological events in real time and in live animals. This technology has greatly advanced our understanding of physiological processes and pathogen-mediated phenomena in specific organs.
In this study, IVM is applied to the mouse liver and protocols are designed to image in vivo the circulatory system of the liver and measure red blood cell (RBC) velocity in individual hepatic vessels. To visualize the different vessel subtypes that characterize the hepatic organ and perform blood flow speed measurements, C57Bl/6 mice are intravenously injected with a fluorescent plasma reagent that labels the liver-associated vasculature. IVM enables in vivo, real time, measurement of RBC velocity in a specific vessel of interest. Establishing this methodology will make it possible to investigate liver hemodynamics under physiological and pathological conditions. Ultimately, this imaging-based methodology will be important for studying the influence of L. donovani infection&#160;on hepatic hemodynamics.
This method can be applied to other infectious models and mouse organs and might be further extended to pre-clinical testing of a drug&#8217;s effect on inflammation by quantifying its effect on blood flow.

Intravital Microscopy Imaging of the Liver following Leishmania Infection: An Assessment of Hepatic Hemodynamics

This article reports on a detailed method for the dynamic measurement and quantification of blood flow velocity within individual blood vessels of the mouse liver vasculature using intravital microscopy imaging in combination with a specific methodology for image acquisition and analysis.

Intravital microscopy (IVM) is a powerful optical imaging technique that has made possible the visualization, monitoring and quantification of various ...

Flow Cytometric Analysis of Natural Killer Cell Lytic Activity in Human Whole Blood

NK cell cytotoxicity is a widely used measure to determine the effect of outside intervention on NK cell function. However, the accuracy and reproducibility of this assay can be considered unstable, either because of user&#39;s errors or because of the sensitivity of NK cells to experimental manipulation. To eliminate these issues, a workflow that reduces them to a minimum was established and is presented here. To illustrate, we obtained blood samples, at various time points, from runners (n = 4) that were submitted to an intense bout of exercise. First, NK cells are simultaneously identified and isolated through CD56 tagging and magnetic-based sorting, directly from whole blood and from as little as one milliliter. The sorted NK cells are removed of any reagent or capping antibodies. They can be counted in order to establish an accurate NK cell count per milliliter of blood. Secondly, the sorted NK cells (effectors cells or E) can be mixed with 3,3&#39;-Diotadecyloxacarbocyanine Perchlorate (DiO) tagged K562 cells (target cells or T) at an assay-optimal 1:5 T:E ratio, and analyzed using an imaging flow-cytometer that allows for the visualization of each event and the elimination of any false positive or false negatives (such as doublets or effector cells). This workflow can be completed in about 4 h, and allows for very stable results even when working with human samples. When available, research teams can test several experimental interventions in human subjects, and compare measurements across several time points without compromising the data&#39;s integrity.

This work describes an advanced workflow for the accurate and fast determination of NK (Natural Killer) cell count and NK cell cytotoxicity in human blood samples.

NK cell cytotoxicity is a widely used measure to determine the effect of outside intervention on NK cell function. However, the accuracy and ...

Visualizing Macrophage Extracellular Traps Using Confocal Microscopy

A primary method used to define the presence of neutrophil extracellular traps (NETs) is confocal microscopy. We have modified established confocal microscopy methods to visualize macrophage extracellular traps (METs). These extracellular traps are defined by the presence of extracellular chromatin with co-expression of other components such as granule proteases, citrullinated histones, and peptidyl arginase deiminase (PAD). The expression of METs is generally measured after exposure to a stimulus and compared to un-stimulated samples. Samples are also included for background and isotype control. Cells are analyzed using well-defined image analysis software. Confocal microscopy may be used to define the presence of METs both in vitro and in vivo in lung tissue.

Macrophage extracellular traps are a newly described entity. This article will concentrate on confocal microscopy methods and how they are visualized in vitro and in vivo from lung samples.

A primary method used to define the presence of neutrophil extracellular traps (NETs) is confocal microscopy. We have modified established confocal ...

Saturated Fatty Acids Induce Ceramide-associated Macrophage Cell Death

Macrophages highly express epidermal fatty acid-binding protein and adipose fatty acid-binding protein. They actively uptake saturated and unsaturated fatty acids, which might play a critical role in regulating their immune functions. Numerous studies have shown that various fatty acids, saturated or unsaturated, may possess different impacts on cell growth and function. However, the approaches used for fatty acid preparation vary, which may lead to non-physiological results. Serum albumin, a natural carrier for fatty acids in mammalian peripheral blood, is recommended for forming a conjugate complex with the sodium salt of fatty acids to study fatty acid function in mammalian cells, thus minimizing the toxicity of fatty acid soap. Thus, a simple, relatively quick heating and sonicating method is developed and presented here for BSA-fatty acid conjugate formation. We describe a protocol using saturated fatty acids, especially stearic acids to induce severe cell death in mouse bone-marrow derived macrophages. We further demonstrate that saturated fatty acid-induced cell death is positively associated with accumulated cellular ceramide levels. This method can be extended for studies of the impact of fatty acid on other mammalian cells.

We illustrate a straight-forward method to derive murine primary macrophages from bone marrow cells and a simple method to prepare BSA-fatty acid conjugates. Then we demonstrate that saturated fatty acids can induce macrophage cell death, and such cell death is positively associated with cellular accumulation of ceramide levels.

Macrophages highly express epidermal fatty acid-binding protein and adipose fatty acid-binding protein. They actively uptake saturated and unsaturated ...