We thank Dr. U. Ashery for the gift of NPY-mRFP cDNA. We thank Drs. M. J. Kofron, L. Mittleman, M. Shaharbani, and Y. Zilberstein for invaluable assistance with microscopy and image analyses. We also thank Dr. Joseph Orly for critical reading of this manuscript. &#160;This work was supported by a grant from the Israel Science Foundation, founded by&#160;the Israel Academy for Sciences (1139/12 to R.S-E.).

1. Preparation of RBL Cell Culture Media
<ol>
	<li>Mix 500 ml of low glucose Dulbecco&#39;s modified Eagle&#39;s medium (DMEM) with 56&#160;ml of fetal bovine serum (this makes 10% FBS), and then add 5.5 ml of penicillin streptomycin (this makes ~1% PEST).</li>
	<li>Filter the media by using 500-1,000 ml Bottle-Top Vacuum Filters with 0.22 &#956;m pore size and store at 4 &#176;C.</li>
</ol>
2. Culture of RBL Cells
<ol>
	<li>Grow RBL cells in a humidified atmosphere of 5% CO2 at 37 &#176;C in either plates or flasks. RBL cells that are growing in 10 cm plates should be supplemented with 10 ml medium and form confluent monolayer of ~107 cells/plate.</li>
	<li>When the cell layer is approaching confluence, replate&#160;the culture at a lower density.
	<ol>
		<li>Remove the culture medium from the plate/flask using a sterile pasteur pipette connected to vacuum.</li>
		<li>Rinse the cell monolayer with prewarmed (37 &#176;C) 0.25% trypsin/EDTA that covers the whole monolayer (the volume depends on the size of culture plate/flask; 2 ml for 10 cm plate). This will detach the cells.</li>
		<li>Alternatively, rinse the cell monolayer with Phosphate buffered saline (PBS), remove the PBS and add prewarmed (37 &#176;C) trypsin/EDTA. This step detaches the cells faster.</li>
		<li>Place the plate/flask in an incubator at 37 &#176;C (no more than 10 min).</li>
		<li>Inspect the cells under the optical microscope to check if they have detached. If the cells did not detach after 10 min, gently tap on the plate/flask.</li>
		<li>Add medium to the culture plate/flask to suspend the cells (the volume of the medium should be at least 2-fold larger than the volume of the trypsin solution).</li>
		<li>Pellet the cells by centrifugation for 3 min at 200 g at 25 &#176;C.</li>
		<li>Resuspend the cells in medium. Dilute the cells by 1:10 and seed in a new culture dish. Incubate the cells for 48-72 hr, until they reach approximately 90% confluence.</li>
		<li>Repeat the same procedure (section 2.2.1-2.2.8) for up to 3 months (30 passages).</li>
	</ol>
	</li>
</ol>
3. Preparation of Transfection Media.
<ol>
	<li>Prepare a 100 mM solution of K-Pipes pH 7, 1 mM solution of Ca2+ acetate and 100 mM solution of Mg2+ acetate.</li>
	<li>Dilute the 100 mM solution of K-Pipes pH 7 into 20 mM using DMEM media, add the 1 mM solution of Ca2+ acetate to a final concentration of 10 &#956;M and 100 mM solution of Mg2+ acetate to a final concentration of 2 mM.</li>
	<li>Weigh&#160;Potassium glutamate and add to the solution to a final concentration of 128 mM, mix well and keep at 4 &#176;C until use. Keep the remaining solutions (i.e., K-Pipes, Ca2+ acetate, Mg2+ acetate) at -20 &#176;C.</li>
</ol>
4. Transfection of RBL Cells
<ol>
	<li>Remove the culture medium from the plate/flask using a sterile pasteur pipette connected to vacuum.</li>
	<li>Rinse the cell monolayer with prewarmed (37 &#176;C) trypsin/EDTA that should cover the whole monolayer. Place the plate/flask in an incubator at 37 &#176;C (no more than 10 min). Check if the cells have detached using the optical microscope.</li>
	<li>Add medium to the culture plate/flask to suspend the cells (the volume of the media should be at least 2-larger more than the volume of the trypsin solution).</li>
	<li>Count the cell number using hemocytometer.</li>
	<li>Pellet 1.5 &#215; 107 cells by centrifugation for 3 min at 200 x g at 25 &#176;C. Discard the supernatants and add 280 &#181;l of transfection medium. Transfer the reaction mix into 4 mm cuvette.</li>
	<li>Add 20 &#956;g of NPY-mRFP plasmid and either 30 &#956;g of control empty plasmid or a tested plasmid. The final volume of the reaction mix should be 300 &#956;l.</li>
	<li>Immediately place on ice for 10 min. Wipe the cuvette from residual water and proceed to electroporation at 300 V for 9 msec.</li>
	<li>For measurements of exocytosis, replate the cells immediately in 24 well tissue culture dishes containing 300 &#956;l medium. Add 8 &#956;l of the reaction mix (4 &#215; 105 cells) to each well. Add 4 &#215; 105 non transfected cells to additional wells for control. Prepare enough wells for to have at least duplicate wells for each treatment for every transfection.</li>
	<li>For time lapse microscopy, replate the cells immediately in an 8-well chamber borosilicate coverglass system containing 80 &#956;l medium. Add 1.5 &#956;l of the reaction mix (7.5 &#215; 104 cells) to each chamber. (Try to avoid using the chambers at the edge of the coverglass, the chambers at the center of the coverglass are easier to image). 
	NOTE: Importantly, not all the cells response to a trigger and occasionally the time-lapse microscopy is abrogated due to loss of focus and drift&#160;of the 8-well chamber borosilicate coverglass system. Therefore, prepare at least 8 chambers for each treatment for each transfection.</li>
	<li>For sensitizing the cells for Fc&#949;RI mediated activation, add 1 &#181;g/ml of mouse DNP specific monoclonal IgE to the media (incubate the cells with IgE for at least 2 hr).</li>
	<li>After 18-24 hr use a fluorescent microscope to confirm that the cells express the plasmids. The excitation and emission wavelengths of mRFP fluorescence are: &#955;Ex 584, &#955;Em 607 nm. NPY-mRFP should appear in vesicular structures which correspond to the SGs.&#160;If the second gene of interest is fused to a fluorescent tag use a fluorescent microscope to confirm the co-expression of both plasmids at the same cells. For example, if the tested gene is fused to GFP, The excitation and emission wavelengths of GFP fluorescence are: &#955;Ex 488, &#955;Em 507 nm. The GFP tagged protein should appear at the same cells that express NPY-mRFP.</li>
	<li>For exocytosis measurements proceed to step 5 and for time lapse microscopy, proceed to step 6.</li>
</ol>
5. Measuring NPY-mRFP Exocytosis
<ol>
	<li>Preparation of Tyrode buffer:
	<ol>
		<li>Prepare a solution of 54 mM KCl, 20 mM MgCl2, 2.74 M NaCl and 8 mM NaH2PO4 in DDW. Mix well and store at 4 &#176;C. This step is for preparation of 20x Tyrode buffer.</li>
		<li>Prepare a solution of 20 mM Hepes pH 7, 1.8 mM CaCl2, 1 mg/ml BSA, 5.6 mM glucose and 1 to 20 dilution of Tyrode 20x in DDW and mix well. This step is for preparation of 1x Tyrode buffer.</li>
		<li>Aliquot the 1x Tyrode buffer and store at -20 &#176;C. Avoid repeated freezing and thawing.</li>
	</ol>
	</li>
	<li>Remove the culture medium from the 24 well plate and wash 3 times with Tyrode buffer. Prepare unstimulated cells by adding 200 &#956;l Tyrode buffer to control wells.</li>
	<li>Prepare 10 &#956;l/well of 20X concentrated activating reagent [(e.g. 1,000 ng/ml DNP-BSA or DNP-HSA (Ag), 200 &#181;M Ca2+ionophore (e.g. A23187), and a combination of 20 &#181;M Ca2+&#160;ionophore and 1,000 nM 12-O-&#160; tetradecanoylphorbol-13-acetate (TPA)]. If the reagents are stored in DMSO, dilute the reagents into 20x concentration in Tyrode buffer containing 1% DMSO.&#160;Incubate at 37 &#176;C for 30 min.</li>
	<li>Remove the supernatants of each well carefully to a 96 well plate, place on ice and avoid from light. (The supernatants contain the chimeric peptide NPY-mRFP that was released from the cells).</li>
	<li>Add 200 &#956;l Tyrode buffer containing 0.5% Triton X-100 to each well and incubate at 37 &#176;C for 10 min. (This step is important for preparation of cell lysates that contain the remaining of NPY-mRFP that was not released from the cells). Collect the cell lysates and transfer to a 96 well plate, place on ice and avoid from light.</li>
	<li>Measure the fluorescence of the cell supernatants and cell lysates using a fluorescence plate reader, using a 590-, 20 nm bandwidth excitation filter and 635-, 35 nm bandwidth emission filter.</li>
	<li>Calculate the percentage of NPY-mRFP released: 
	NOTE: The fluorescence reader measure arbitrary fluorescence units (AFU). AFU values depend on the machine and its sensitivity and the transfection efficiency.
	<ol>
		<li>Set the autofluorescence of nontransfected RBL cells as blank. Divide the AFU of each supernatant to the total fluorescence (AFU of the supernatants + AFU of the corresponding lysate) and multiply by 100.</li>
	</ol>
	</li>
</ol>
6. Time-lapse Microscopy of Exocytosis
<ol>
	<li>Seed 7.5 &#215; 104 of the transfected cells/chamber in an 8-well chamber borosilicate coverglass system. After 18-24 hr, remove the culture medium from the chambers and wash 3 times with Tyrode buffer</li>
	<li>Add 72 &#956;l of Tyrode buffer to each chamber. Dilute the activating reagents in Tyrode buffer to 10x concentration.</li>
	<li>Use a confocal fluorescence microscope equipped with a heated chamber (37 &#176;C) and CO2 controller (4.8%) and a 40X or 63X objective. Turn on the microscope systems: mercury lamp, computer, and lasers. Make sure that the heated chamber is at the right temperature before starting the experiment.</li>
	<li>Place the chamber in the heated chamber and make sure that the chamber is installed correctly and stable.</li>
	<li>Turn on the fluorescence light according to the relevant fluorophore and visualize transfected cells. Turn off fluorescence once a cell of interest is in the field in order to minimize bleaching and cytotoxicity. It is important that this field will contain about 2-3 transfected cells. The transfected cells should be well spread but not touching each other.</li>
	<li>Adjust the laser power (depending on the microscope) to minimize noise and oversaturation as well as toxicity, and set the gain and offset to modify the signal to noise ratio. Scan fast in order to minimize the duration of laser exposition (average 2).</li>
	<li>Adjust the pinhole size to a maximum, this enables decreasing the laser power and to maintain images focused for a long period of time. If desired, set the parameters for the Z stack to reconstruct the image in three dimensional, adjust the pinhole size to 1 airy unit (AU) that gives the best signal to noise ratio and acquire successive scanning of two-dimensional confocal optical slices in the z-axes with optical slices &#8804;0.7 &#956;m.</li>
	<li>Set the interval time between each acquisition to 15-30 sec and the duration of total acquisition to 15&#160;min and start acquiring images. After 5&#160;min of acquisition pause the time series. Add 8 &#956;l of the 10x trigger and continue the acquisition immediately.</li>
	<li>Save the pictures, perform deconvolution using a deconvolution software and reconstruct the stacks to three dimensional images and to a movie using Imaris software.</li>
</ol>
7. Image Analyses
<ol>
	<li>Import the data from the deconvoluted time series images that were obtained by the confocal fluorescence microscope to Imaris software. This software reads more than 40 microscopy files. If the software cannot read the files; convert the files to tif files and import.</li>
	<li>To add time points to the end of an open data set press edit -&#62; Add Time Points and import the new data set.</li>
	<li>Create surface of the mRFP channel using surface wizard option. Choose the default algorithm. Choose the channel of NPY-mRFP. Mark the smoothing option to reduce noise. To avoid loss of small details reduce the area detail level to 0.05 &#956;m.</li>
	<li>Set the intensity threshold. New gray surface will be displayed. Go to &#8220;Settings&#8221; and switch the style from &#8220;Center point&#8221; to &#8220;Surface&#8221;.</li>
	<li>Go to the statistic tab in the properties of selected object, select the detailed tab and the specific value such as fluorescence intensity, volume etc.</li>
	<li>Review the data and confirm that the values are compatible with the images. For example, two or more adjacent granules might be measured as one bigger granule. For quantifying the average granule size divide the size of the merged granules to the actual number of granules.</li>
	<li>Export the desired data sets to Excel files and analyze the data.</li>
</ol>f

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The authors have no financial conflicts of interest.

We describe an innovative strategy that combines quantification of MCs exocytosis and four (x, y, z, t) dimension quantifications by time-lapsed three-dimensional imaging of the SGs in living cells using a reporter gene for exocytosis. This technique enables screening of families of proteins for their impact on MC function such as monitoring SGs starting as early as their exit from the Golgi through their maturation, acquisition of exocytosis competence and degranulation. The combination of&#160;measurements of exocytosi...

Mast Cells (MC) are immune cells that are best known for their involvement in allergic and inflammatory reactions such as arthritis, asthma, eosinophilic esophagitis, chronic dermatitis and anaphylactic shock 1,2 as well as other pathologies including coronary artery disease 3,5 and cancer 3,4. In addition, MCs play important roles in innate and adaptive immunity, both in host defense against bacteria and parasites and by suppression of immune responses, for example inducing allograft tolerance 5,6 .
MCs originate from the bone marrow, developing from CD34+/CD117+ pluripotent progenitor cells 7. Committed bone marrow MC&#160;progenitors are released into the bloodstream and migrate into the peripheral tissues localizing predominantly within connective tissues and epithelial surfaces 8. Maturation and terminal differentiation are eventually achieved under the influence of cytokines within the surrounding milieu 8,9 .
MCs can be activated by an allergen (antigen, Ag), whose encounter resulted in the generation of immunoglobulin E (IgE) type antibodies. Binding of such IgE to the MC&#8217;s Fc&#949;RI receptors, followed by cross-linking of cell bound IgE upon re-exposure to the same Ag, results in Fc&#949;RI aggregation and initiation of a signaling cascade that culminates in cell degranulation [reviewed in 10,11]. MCs are also activated, independently of IgE, by neuropeptides 5,12, toxins 13 , bacterial and viral antigens 14,15, a number of positively charged peptides collectively referred to as basic secretagogues, immune cells and cytokines 5,13,12,16,17. MCs are also activated by many of their own released mediators, which further amplify the inflammatory response.
MCs are packed with secretory granules (SGs) that contain immunoregulatory mediators, including vasoactive amines, such as histamine and serotonin (in rodents), proteoglycans, proteases, such as chymase and tryptase, vascular endothelial growth factor and several cytokines and chemokines 8,9. These mediators are &#8220;ready to go&#8221; and once MCs are activated by an appropriate stimulus, these mediators are released from the cells by regulated exocytosis (degranulation) in a matter of seconds to minutes 18,19. This initial event is followed by the de novo synthesis and release of a large array of biologically potent substances, including arachidonic acid metabolites, multiple cytokines and chemokines 20,21,22. Release of newly synthesized products occurs independently of SG release. Collectively, these mediators initiate early and late phase inflammatory and allergic responses. Therefore, understanding the mechanisms accounting for MC activation and degranulation are both of theoretical and clinical importance.
The difficulty to genetically manipulate primary and cultured MCs has hampered the attempts to elucidate the mechanisms underlying MC degranulation, which remained poorly resolved. To overcome this problem we developed a reporter based assay by co-transfecting the mucosal mast cell line, rat basophilic leukemia (RBL)-2H3 (herein referred to as RBL) or bone marrow derived MCs&#160;(BMMCs) 30 with a gene of interest and Neuropeptide Y (NPY) fused to monomeric RFP (mRFP), as a SG reporter.
NPY was previously shown to recapitulate the behavior of endogenous SG markers in other systems. Moreover, because mRFP fluorescence is pH insensitive, expression of NPY-mRFP allows visualization of the acidic SGs as well as quantitative assessment of exocytosis by using 96-well plates and a fluorescence plate reader. We have shown that NPY-mRFP is delivered to the acidic SGs of RBL cells and BMMCs and is released from the cells in a regulated fashion alongside the endogenous SG&#160;cargo (i.e., &#946;-hexosaminidase and serotonin) 30,32 . This protocol provides a high-resolution imaging-based methodology that allows screening genes of interest for their phenotypic and functional impact on SG characteristics and degranulation in RBL cells 32. Specifically, this protocol allows real time tracking of MC SGs and quantification of their area or volume size, their number, kinetics of assembly, their movement along the cell cytoskeleton and their ultimate fusion with the plasma membrane under different conditions. For example, sensitizing the cells with DNP-specific IgE and triggering the cells with a multivalent Ag (DNP conjugated serum albumin) under different perturbations (i.e., knockdown of genes of interest, over expression of wt or mutant genes, or pharmacological manipulations) and comparing to control cells.

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	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:421px;">Name of Material/ Equipment</td>
			<td style="width:128px;">Company</td>
			<td style="width:139px;">Catalog Number</td>
			<td style="width:156px;">Comments/Description</td>
		</tr>
		<tr height="35">
			<td height="35" style="height:35px;width:421px;">DMEM</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td>D6046-500ML</td>
			<td style="width:156px;">Warm in 37 &#176;C water bath before use</td>
		</tr>
		<tr height="35">
			<td height="35" style="height:35px;">Fetal Bovine Serum</td>
			<td style="width:128px;">GE health care Life sciences</td>
			<td>SH30071.01</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Penicillin-Streptomycin</td>
			<td style="width:128px;">Life technologies</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:421px;">Cellulose acetate membrane, pore size 0.22&#160;&#956;m</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td height="20" style="height:20px;width:139px;">CLS430769-1EA</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Corning tissue-culture treated culture dishes</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td height="20" style="height:20px;width:139px;">CLS430167</td>
			<td></td>
		</tr>
		<tr height="35">
			<td height="35" style="height:35px;">Trypsin/EDTA Solution (TE)</td>
			<td style="width:128px;">Life technologies</td>
			<td>R001100</td>
			<td style="width:156px;">Warm in 37 &#176;C water bath before use</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:421px;">PIPES dipotassium salt</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td height="20" style="height:20px;width:139px;">108321-27-3&#160;</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:421px;">Calcium acetate hydrate</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td>114460-21-8</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:421px;">Magnesium acetate tetrahydrate</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td height="20" style="height:20px;width:139px;">M5661&#160;</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:421px;">L-Glutamic acid potassium salt monohydrate (Potassium glutamate)</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td height="20" style="height:20px;width:139px;">G1501</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">4 mm electroporation cuvettes</td>
			<td style="width:128px;">cell projects</td>
			<td style="width:139px;">EP-104</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">GENE PULSER WITH PULSE CONTROLLER &#38; CAPACITANCE</td>
			<td style="width:128px;">Bio rad</td>
			<td style="width:139px;"></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Chambered coverglass</td>
			<td style="width:128px;">Thermo scientific</td>
			<td align="right" style="width:139px;">155411</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:421px;">24 well, flat bottom</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td height="20" style="height:20px;width:139px;">CLS3524</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:421px;">Corning 96 well plates</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td height="20" style="height:20px;width:139px;">CLS3367 or CLS390</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">96 well plate fluorescence reader- Infinite 200</td>
			<td style="width:128px;">Tecan</td>
			<td style="width:139px;"></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Calcium ionophore A23187</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td height="20" style="height:20px;width:139px;">C7522</td>
			<td>Avoid from direct light exposure</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">12-O-tetradecanoyl-13-acetate (TPA)</td>
			<td>Calbiochem</td>
			<td height="20" style="height:20px;width:139px;">P3766</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">anti-DNP monoclonal IgE</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td>D8406&#160;</td>
			<td height="20" style="height:20px;width:156px;"></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">DNP-BSA/ DNP-HAS</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td style="width:139px;">A6661</td>
			<td>Avoid from direct light exposure</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:421px;">Triton-x-100</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td style="width:139px;">T8787</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:421px;">Confocal fluorescent microscope:</td>
			<td style="width:128px;"></td>
			<td style="width:139px;"></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:421px;">Zeiss LSM 510</td>
			<td style="width:128px;"></td>
			<td style="width:139px;"></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:421px;">Leica</td>
			<td style="width:128px;">SP5</td>
			<td style="width:139px;"></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Nikon A1 inverted</td>
			<td style="width:128px;"></td>
			<td style="width:139px;"></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:421px;">Imaris software</td>
			<td style="width:128px;">BITLANE</td>
			<td style="width:139px;"></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:421px;">Microsoft exel or Prism or other analyses software</td>
			<td style="width:128px;"></td>
			<td style="width:139px;"></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:421px;">Other reagent:</td>
			<td style="width:128px;"></td>
			<td style="width:139px;"></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:421px;">Magnesium Chloride</td>
			<td style="width:128px;">MERK</td>
			<td style="width:139px;">5833</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:421px;">Sodium chloride</td>
			<td style="width:128px;">MERK</td>
			<td style="width:139px;">6404</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:421px;">Calcium chloride&#160;</td>
			<td style="width:128px;">MERK</td>
			<td style="width:139px;">2382</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Bovine serum albumin&#160;</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td style="width:139px;">A4503</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:421px;">Glucose</td>
			<td style="width:128px;">BDH Laboratories</td>
			<td style="width:139px;">284515V</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Monosodium phosphate&#160;</td>
			<td style="width:128px;">MERK</td>
			<td style="width:139px;">5345</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:421px;">Sterile water</td>
			<td style="width:128px;"></td>
			<td style="width:139px;"></td>
			<td></td>
		</tr>
	</tbody>
</table>

investigating mast cell secretory granules; from biosynthesis to exocytosis

Mast Cells (MC) are secretory cells of the immune system that accomplish their physiological and pathological functions by releasing pre-formed and newly synthesized allergic, inflammatory and immunoregulatory mediators. MCs&#8217; mediators affect multiple tissues and organs culminating in allergic and immune responses. The synthesis, storage and release of the MC mediators are highly regulated. The pre-formed mediators are packed in cytoplasmic secretory granules&#160;(SG) that fuse with the plasma membrane and release their content by regulated exocytosis. We present a protocol, based on the co-expression of a gene of interest with a reporter gene that is targeted to the SGs and is released in a regulated fashion alongside the endogenous SG mediators. The protocol enables high resolution four dimensional confocal analyses of the MC SGs and monitoring their timeline from biogenesis to triggered exocytosis. Thus, using this protocol for screening genes of interest for their phenotypic and functional impact allows deciphering the molecular mechanisms that govern the biogenesis and exocytosis of the MC SGs and identifying the regulators involved. Thereby, further insights into the cellular mechanisms that account for MCs function in health and disease should be provided.

Because of the low transfection efficiency of MCs, genetic manipulations are unlikely to leave an impact on readouts of average secretion measured by endogenous SGs mediators. Nevertheless, by establishing complete co-expression of the reporter gene NPY-mRFP and the co-transfected plasmid at the same cells, monitoring of NPY-mRFP results in monitoring exclusively the cell population that expresses the gene of interest. Therefore, the advantage of this assay compared to conventional methods is the ability to selectively m...

Watch this Scientific Journal Video about Investigating Mast Cell Secretory Granules; from Biosynthesis to Exocytosis at JoVE.com

Investigating Mast Cell Secretory Granules; from Biosynthesis to Exocytosis

The goal of the present&#160;protocol was to develop a method that will allow functional genomic analyses of mast cell secretion. The protocol is based on quantitative assessment of the release of a fluorescent reporter gene cotrasfected with the gene of interest and real time&#160;analyses of the secretory granule&#39;s morphology.

Mast Cells (MC) are secretory cells of the immune system that accomplish their physiological and pathological functions by releasing pre-formed and newly ...

investigating-mast-cell-secretory-granules-from-biosynthesis-to

Research

JoVE Journal

Immunology and Infection

13.0K Views.  Sackler Faculty of Medicine, Tel Aviv University. The goal of the present protocol was to develop a method that will allow functional genomic analyses of mast cell secretion. The protocol is based on quantitative assessment of the release of a fluorescent reporter gene cotrasfected with the gene of interest and real time analyses of the secretory granule's morphology.

Video: Investigating Mast Cell Secretory Granules; from Biosynthesis to Exocytosis

Clinical Application of Sleeping Beauty and Artificial Antigen Presenting Cells to Genetically Modify T Cells from Peripheral and Umbilical Cord Blood

The potency of clinical-grade T cells can be improved by combining gene therapy with immunotherapy to engineer a biologic product with the potential for superior (i) recognition of tumor-associated antigens (TAAs), (ii) persistence after infusion, (iii) potential for migration to tumor sites, and (iv) ability to recycle effector functions within the tumor microenvironment. Most approaches to genetic manipulation of T cells engineered for human application have used retrovirus and lentivirus for the stable expression of CAR1-3. This approach, although compliant with current good manufacturing practice (GMP), can be expensive as it relies on the manufacture and release of clinical-grade recombinant virus from a limited number of production facilities. The electro-transfer of nonviral plasmids is an appealing alternative to transduction since DNA species can be produced to clinical grade at approximately 1/10th the cost of recombinant GMP-grade virus. To improve the efficiency of integration we adapted Sleeping Beauty (SB) transposon and transposase for human application4-8. Our SB system uses two DNA plasmids that consist of a transposon coding for a gene of interest (e.g. 2nd generation CD19-specific CAR transgene, designated CD19RCD28) and a transposase (e.g. SB11) which inserts the transgene into TA dinucleotide repeats9-11. To generate clinically-sufficient numbers of genetically modified T cells we use K562-derived artificial antigen presenting cells (aAPC) (clone #4) modified to express a TAA (e.g. CD19) as well as the T cell costimulatory molecules CD86, CD137L, a membrane-bound version of interleukin (IL)-15 (peptide fused to modified IgG4 Fc region) and CD64 (Fc-&gamma; receptor 1) for the loading of monoclonal antibodies (mAb)12. In this report, we demonstrate the procedures that can be undertaken in compliance with cGMP to generate CD19-specific CAR+ T cells suitable for human application. This was achieved by the synchronous electro-transfer of two DNA plasmids, a SB transposon (CD19RCD28) and a SB transposase (SB11) followed by retrieval of stable integrants by the every-7-day additions (stimulation cycle) of &gamma;-irradiated aAPC (clone #4) in the presence of soluble recombinant human IL-2 and IL-2113. Typically 4 cycles (28 days of continuous culture) are undertaken to generate clinically-appealing numbers of T cells that stably express the CAR. This methodology to manufacturing clinical-grade CD19-specific T cells can be applied to T cells derived from peripheral blood (PB) or umbilical cord blood (UCB). Furthermore, this approach can be harnessed to generate T cells to diverse tumor types by pairing the specificity of the introduced CAR with expression of the TAA, recognized by the CAR, on the aAPC.

Clinical Application of Sleeping Beauty and Artificial Antigen Presenting Cells to Genetically Modify T Cells from Peripheral and Umbilical Cord Blood

T cells expressing a CD19-specific chimeric antigen receptor (CAR) are infused as investigational treatment of B-cell malignancies in our first-in-human gene therapy trials. We describe genetic modification of T cells using the Sleeping Beauty (SB) system to introduce CD19-specific CAR and selective propagation on designer CD19+ artificial antigen presenting cells.

The potency of clinical-grade T cells can be improved by combining gene therapy with immunotherapy to engineer  a biologic product with the potential for ...

Isolation of Precursor B-cell Subsets from Umbilical Cord Blood

Umbilical cord blood is highly enriched for hematopoietic progenitor cells at different lineage commitment stages. We have developed a protocol for isolating precursor B-cells at four different stages of differentiation. Because genes are expressed and epigenetic modifications occur in a tissue specific manner, it is vital to discriminate between tissues and cell types in order to be able to identify alterations in the genome and the epigenome that may lead to the development of disease. This method can be adapted to any type of cell present in umbilical cord blood at any stage of differentiation.	
This method comprises 4 main steps. First, mononuclear cells are separated by density centrifugation. Second, B-cells are enriched using biotin conjugated antibodies that recognize and remove non B-cells from the mononuclear cells. Third the B-cells are fluorescently labeled with cell surface protein antibodies specific to individual stages of B-cell development. Finally, the fluorescently labeled cells are sorted and individual populations are recovered. The recovered cells are of sufficient quantity and quality to be utilized in downstream nucleic acid assays.

Here we describe a protocol for isolating subsets of precursor B-cells from umbilical cord blood. A sufficient quantity and quality of nucleic acids may be extracted from the cells and used in subsequent assays utilizing DNA or RNA.

Umbilical cord blood is highly enriched for hematopoietic progenitor cells at different lineage commitment stages. We have developed a protocol for ...

A Microplate Assay to Assess Chemical Effects on RBL-2H3 Mast Cell Degranulation: Effects of Triclosan without Use of an Organic Solvent

Mast cells play important roles in allergic disease and immune defense against parasites. Once activated (e.g. by an allergen), they degranulate, a process that results in the exocytosis of allergic mediators. Modulation of mast cell degranulation by drugs and toxicants may have positive or adverse effects on human health. Mast cell function has been dissected in detail with the use of rat basophilic leukemia mast cells (RBL-2H3), a widely accepted model of human mucosal mast cells3-5. Mast cell granule component and the allergic mediator &#946;-hexosaminidase, which is released linearly in tandem with histamine from mast cells6, can easily and reliably be measured through reaction with a fluorogenic substrate, yielding measurable fluorescence intensity in a microplate assay that is amenable to high-throughput studies1. Originally published by Naal et al.1, we have adapted this degranulation assay for the screening of drugs and toxicants and demonstrate its use here.
Triclosan is a broad-spectrum antibacterial agent that is present in many consumer products and has been found to be a therapeutic aid in human allergic skin disease7-11, although the mechanism for this effect is unknown. Here we demonstrate an assay for the effect of triclosan on mast cell degranulation. We recently showed that triclosan strongly affects mast cell function2. In an effort to avoid use of an organic solvent, triclosan is dissolved directly into aqueous buffer with heat and stirring, and resultant concentration is confirmed using UV-Vis spectrophotometry (using &#949;280 = 4,200 L/M/cm)12. This protocol has the potential to be used with a variety of chemicals to determine their effects on mast cell degranulation, and more broadly, their allergic potential.

Mast cell degranulation, the release of allergic mediators, is important in allergy, asthma, and parasite defense. Here we demonstrate techniques1 for assessing effects of drugs and toxicants on degranulation, methodology recently utilized to exhibit the powerful inhibitory effect of antibacterial agent triclosan2.

Mast cells play important roles in allergic disease and immune defense against parasites. Once activated (e.g. by an allergen), they degranulate, a ...

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 ...

Analyzing the Functions of Mast Cells In Vivo Using 'Mast Cell Knock-in' Mice

Mast cells (MCs) are hematopoietic cells which reside in various tissues, and are especially abundant at sites exposed to the external environment, such as skin, airways and gastrointestinal tract. Best known for their detrimental role in IgE-dependent allergic reactions, MCs have also emerged as important players in host defense against venom and invading bacteria and parasites. MC phenotype and function can be influenced by microenvironmental factors that may differ according to anatomic location and/or based on the type or stage of development of immune responses. For this reason, we and others have favored in vivo approaches over in vitro methods to gain insight into MC functions. Here, we describe methods for the generation of mouse bone marrow-derived cultured MCs (BMCMCs), their adoptive transfer into genetically MC-deficient mice, and the analysis of the numbers and distribution of adoptively transferred MCs at different anatomical sites. This method, named the &#8216;mast cell knock-in&#8217; approach, has been extensively used over the past 30 years to assess the functions of MCs and MC-derived products in vivo. We discuss the advantages and limitations of this method, in light of alternative approaches that have been developed in recent years.

Analyzing the Functions of Mast Cells In Vivo Using &#039;Mast Cell Knock-in&#039; Mice

We describe a method for the generation of in vitro derived mast cells, their engraftment into mast cell-deficient mice, and the analysis of the phenotype, numbers and distribution of engrafted mast cells at different anatomical sites. This protocol can be used to assess the functions of mast cells in vivo.

Mast cells (MCs) are hematopoietic cells which reside in various tissues, and are especially abundant at sites exposed to the external environment, such ...

Overexpression and Purification of Human Cis-prenyltransferase in Escherichia coli

Prenyltransferases (PT) are a group of enzymes that catalyze chain elongation of allylic diphosphate using isopentenyl diphosphate (IPP) via multiple condensation reactions. DHDDS (dehydrodolichyl diphosphate synthase) is a eukaryotic long-chain cis-PT (forming cis double bonds from the condensation reaction) that catalyzes chain elongation of farnesyl diphosphate (FPP, an allylic diphosphate) via multiple condensations with isopentenyl diphosphate (IPP). DHDDS is of biomedical importance, as a non-conservative mutation (K42E) in the enzyme results in retinitis pigmentosa, ultimately leading to blindness. Therefore, the present protocol was developed in order to acquire large quantities of purified DHDDS, suitable for mechanistic studies. Here, the usage of protein fusion, optimized culture conditions and codon-optimization were used to allow the overexpression and purification of functionally active human DHDDS in E. coli. The described protocol is simple, cost-effective and time sparing. The homology of cis-PT among different species suggests that this protocol may be applied for other eukaryotic cis-PT as well, such as those involved in natural rubber synthesis.

Overexpression and Purification of Human Cis-prenyltransferase in Escherichia coli

A simple protocol for overexpression and purification of codon-optimized, human cis-prenyltransferase, under non-denaturing conditions, from Escherichia coli, is described, along with an enzymatic activity assay. This protocol can be generalized for production of other cis- prenyltransferase proteins in quantity and quality suitable for mechanistic studies.

Prenyltransferases (PT) are a group of enzymes that catalyze chain elongation of allylic diphosphate using isopentenyl diphosphate (IPP) via multiple ...

Isolation of Peritoneum-derived Mast Cells and Their Functional Characterization with Ca2+-imaging and Degranulation Assays

Mast cells (MCs), as a part of the immune system, play a key role in defending the host against several pathogens and in the initiation of the allergic immune response. The activation of MCs via the cross-linking of surface IgE bound to high affinity IgE receptor (Fc&#949;RI), as well as through the stimulation of several other receptors, initiates the rise of the free intracellular Ca2+ level ([Ca2+]i) that promotes the release of inflammatory and allergic mediators. The identification of molecular constituents involved in these signaling pathways is crucial for understanding the regulation of MC function. In this article, we describe a protocol for the isolation of murine connective tissue type MCs by peritoneal lavage and cultivation of peritoneal MCs (PMCs). Cultures of MCs from various knockout mouse models by this methodology represent a useful approach to the identification of proteins involved in MC signaling pathways. In addition, we also describe a protocol for single cell Fura-2 imaging as an important technique for the quantification of Ca2+ signaling in MCs. Fluorescence-based monitoring of [Ca2+]i is a reliable and commonly used approach to study Ca2+ signaling events, including store-operated calcium entry, which is of utmost importance for MC activation. For the analysis of MC degranulation, we describe a &#946;-hexosaminidase release assay. The amount of &#946;-hexosaminidase released into the culture medium is considered as a degranulation marker for all three different secretory subsets described in MCs. &#946;-hexosaminidase can easily be quantified by its reaction with a colorigenic substrate in a microtiter plate colorimetric assay. This highly reproducible technique is cost-effective and requires no specialized equipment. Overall, the provided protocol demonstrates a high yield of MCs expressing typical MC surface markers, displaying typical morphological and phenotypic features of MCs, and demonstrating highly reproducible responses to secretagogues in Ca2+-imaging and degranulation assays.

Isolation of Peritoneum-derived Mast Cells and Their Functional Characterization with Ca2+-imaging and Degranulation Assays

Here, we present a protocol to isolate and cultivate murine peritoneal mast cells. We also describe two protocols for their functional characterization: a fluorescent imaging of intracellular free Ca2+ concentration and a degranulation assay based on colorimetric quantification of the released &#946;-hexosaminidase.

Mast cells (MCs), as a part of the immune system, play a key role in defending the host against several pathogens and in the initiation of the allergic ...

Investigating Aortic Valve Calcification via Isolation and Culture of T Lymphocytes using Feeder Cells from Irradiated Buffy Coat

Calcific aortic valve disease (CAVD), an active disease process ranging from mild thickening of the valve to severe calcification, is associated with high mortality, despite new therapeutic options such as transcatheter aortic valve replacement (TAVR). 
The complete pathways that start with valve calcification and lead to severe aortic stenosis remain only partly understood. By providing a close representation of the aortic valve cells in vivo, the assaying of T lymphocytes from stenotic valve tissue could be an efficient way to clarify their role in the development of calcification. After surgical excision, the fresh aortic valve sample is dissected in small pieces and the T lymphocytes are cultured, cloned then analyzed using fluorescence activated cell sorting (FACS).
The staining procedure is simple and the stained tubes can also be fixed using 0.5% of paraformaldehyde and analyzed up to 15 days later. The results generated from the staining panel can be used to track changes in T cell concentrations over time in relation to intervention and could easily be further developed to assess activation states of specific T cell subtypes of interest. In this study, we show the isolation of T cells, performed on fresh calcified aortic valve samples and the steps of analyzing T cell clones using flow cytometry to further understand the role of adaptive immunity in CAVD pathophysiology.

In this study, we describe the process of T lymphocyte isolation from fresh samples of calcified aortic valves and the analytical steps of T cell-cloning for the characterization of the adaptive leukocyte subsets by using flow cytometry analysis.

Calcific aortic valve disease (CAVD), an active disease process ranging from mild thickening of the valve to severe calcification, is associated with high ...

Double Labeling Immunofluorescence using Antibodies from the Same Species to Study Host-Pathogen Interactions

Nowadays, it is possible to find a wide range of molecular tools available to study parasite-host cell interactions. However, some limitations exist to obtain commercial monoclonal or polyclonal antibodies that recognize specific cell structures and proteins in parasites. Besides, there are few commercial antibodies available to label trypanosomatids. Usually, polyclonal antibodies against parasites are prepared in-house and could be more challenging to use in combination with other antibodies produced in the same species. Here, the protocol demonstrates how to use polyclonal and monoclonal antibodies raised in the same species to perform double labeling immunofluorescence to study host cell and pathogen interactions. To achieve the double labeling immunofluorescence, it is crucial to incubate first the mouse polyclonal antibody and then follow the incubation with the secondary mouse IgG antibody conjugated to any fluorochrome. After that, an additional blocking step is necessary to prevent any trace of the primary antibody from being recognized by the next secondary antibody. Then, a mouse monoclonal antibody and its specific IgG subclass secondary antibody conjugated to a different fluorochrome are added to the sample at the appropriate times. Additionally, it is possible to perform triple labeling immunofluorescence using a third antibody raised in a different species. Also, structures such as nuclei and actin can be stained subsequently with their specific compounds or labels. Thus, these approaches presented here can be adjusted for any cell whose sources of primary antibodies are limited.

Here, the protocol describes how to perform double labeling immunofluorescence using primary antibodies raised in the same species to study host-pathogen interactions. Also, it can include the third antibody from a different host in this protocol. This approach can be made in any cell type and pathogens.

Nowadays, it is possible to find a wide range of molecular tools available to study parasite-host cell interactions. However, some limitations exist to ...

Investigating the Phagocytosis of Leishmania using Confocal Microscopy

Phagocytosis is an orchestrated process that involves distinct steps: recognition, binding, and internalization. Professional phagocytes take up Leishmania parasites by phagocytosis, consisting of recognizing ligands on parasite surfaces by multiple host cell receptors. Binding of Leishmania to macrophage membranes occurs through complement receptor type 1 (CR1) and complement receptor type 3 (CR3) and Pattern Recognition Receptors. Lipophosphoglycan (LPG) and 63 kDa glycoprotein (gp63) are the main ligands involved in macrophage-Leishmania interactions. Following the initial recognition of parasite ligands by host cell receptors, parasites become internalized, survive, and multiply within parasitophorous vacuoles. The maturation process of Leishmania-induced vacuoles involves the acquisition of molecules from intracellular vesicles, including monomeric G protein Rab 5 and Rab 7, lysosomal associated membrane protein 1 (LAMP-1), lysosomal associated membrane protein 2 (LAMP-2), and microtubule-associated protein 1A/1B-light chain 3 (LC3).
Here, we describe methods to evaluate the early events occurring during Leishmania interaction with the host cells using confocal microscopy, including (i) binding (ii) internalization, and (iii) phagosome maturation. By adding to the body of knowledge surrounding these determinants of infection outcome, we hope to improve the understanding of the pathogenesis of Leishmania infection and support the eventual search for novel chemotherapeutic targets.

Investigating the Phagocytosis of Leishmania using Confocal Microscopy

The mechanism associated with phagocytosis in Leishmania infection remains poorly understood. Here, we describe methods to evaluate the early events occurring during Leishmania interaction with the host cells.