N.G. is the recipient of fellowships from the French &#8220;Fondation pour la Recherche M&#233;dicale FRM&#8221; and the Philipp Foundation; R.S. is supported by the Lucile Packard Foundation for Children&#8217;s Health and the Stanford NIH/NCRR CTSA award number UL1 RR025744; P.S. is supported by a Max Kade Fellowship of the Max Kade Foundation and the Austrian Academy of Sciences and a Schroedinger Fellowship of the Austrian Science Fund (FWF): J3399-B21; S.J.G. acknowledges support from National Institutes of Health grants U19 AI104209, NS 080062 and from Tobacco-Related Disease Research Program at University of California; L.L.R. acknowledges support from the Arthritis National Research Foundation (ANRF) and National Institutes of Health grant K99AI110645.

All animal care and experimentation were conducted in compliance with the guidelines of the National Institutes of Health and with the specific approval of the Institutional Animal Care and Use Committee of Stanford University.
1. Generation and Characterization of Bone Marrow-derived Cultured Mast Cells (BMCMCs).
Note: Donor BMCMCs should be generated from bone marrow cells of the same genetic background as the recipient MC-deficient mice. Male-derived donor BMCMCs are not suitable for engraftment of female mice. Female-derived donor BMCMCs will successfully engraft into both male and female recipients.
<ol>
	<li>Bone Marrow Extraction.
	<ol>
		<li>Pour sterile phosphate-buffered saline (PBS) into 6 well culture plate (1 well per mouse) and place on ice.</li>
		<li>Soak the dissection instruments in 70% ethanol for sterilization.</li>
		<li>Euthanize donor mice by carbon dioxide (CO2) inhalation followed by cervical dislocation, then spray the mice with 70% ethanol at the sites of manipulation.</li>
		<li>Use sterile dissection instruments to extract the femur, tibia and fibula bones without cutting any bone epiphyses.</li>
		<li>While securing the bones with a forceps, scrape off all tissue from bones (and discard fibula) using sterile scissors (or scalpel blades). Place bones in PBS on ice until all bones are collected.</li>
		<li>Carry out all remaining steps in sterile tissue culture hood. Using sterile instruments, secure bones with forceps and cut off both epiphyses to expose the medullary cavity.</li>
		<li>Using 3 ml syringes and 30 G needles, and cold flushing medium (Dulbecco Modified Eagle Medium [DMEM] supplemented with 10% fetal calf serum [FCS, heat-inactivated], 2 mM L-glutamine, 1% antibiotic-antimycotic solution, 50 &#181;M &#914;-mercaptoethanol), flush the red bone marrow into a Petri dish.</li>
		<li>Use the same syringe to dissociate flushed bone marrow cell clusters by repeated gentle aspiration and ejection.</li>
		<li>Pool femoral and tibial bone marrow from each mouse into one 15 ml centrifuge tube. Fill the tube with cold flushing medium to wash bone marrow cells and centrifuge at 400 x g for 5 min at 4 &#176;C.</li>
	</ol>
	</li>
	<li>BMCMCs Culture.
	<ol>
		<li>Remove supernatant and recover pelleted bone marrow cells in 10 ml of culture medium (DMEM supplemented with 10% fetal calf serum [FCS, heat-inactivated], 2 mM L-glutamine, 1% antibiotic-antimycotic solution, 50 &#181;M &#914;-mercaptoethanol and 20% WEHI-3 cell-conditioned medium [as a source of IL-3; alternatively use recombinant mouse IL-3 at 10 ng/ml]).</li>
		<li>Place cells in tissue culture flask of appropriate size (e.g., T25 for 1 mouse, T75 for 2 mice, etc.).</li>
		<li>1-2 days after plating cells, transfer medium and suspension cells (leaving debris and adherent cells sticking to bottom of flask) to a new flask and add fresh culture medium (10 ml/mouse).</li>
		<li>During the following weeks, feed cells every 3-4 days (add 10 ml of culture medium per mouse). Maintain cell density between 2.5 x 105-1 x 106 cells/ml. Transfer non-adherent cells to a new flask once a week until no adherent cells are present in the culture flask. Test maturity of cells (see below) before use for in vitro assays or engraftment into MC-deficient mice. 
		NOTE: Complete differentiation of BMCMCs will take 4-6 weeks.</li>
	</ol>
	</li>
	<li>Assessment of BMCMC maturity.
	<ol>
		<li>Using flow cytometry.
		<ol>
			<li>Wash cells (5 x 104-5 x 105 cells/condition) with ice-cold FACS buffer (PBS, 0.5% FCS) in 5 ml polystyrene round bottom tube. Centrifuge at 400 x g for 5 min at 4 &#176;C. Aspirate supernatant.</li>
			<li>Dilute anti-mouse CD16/32 (clone 93 or 2.4G2) monoclonal antibodies 1:200 (2.5 &#956;g/ml) in FACS buffer. Add 10 &#181;l to each pellet and resuspend by brief vortexing. Incubate 5 min on ice to block Fc binding. 
			NOTE: Protect samples from direct light for all remaining steps.</li>
			<li>Dilute phycoerythrin (PE) conjugated anti-mouse Fc &#949;RI &#945; (clone MAR-1) 1:200 (1 &#956;g/ml) and fluorescein isothiocyanate (FITC) conjugated anti-mouse KIT (CD117; clone 2B8) 1:200 (2.5 &#956;g/ml) (&#8220;staining solution&#8221;), or the respective labeled isotype control antibodies in FACS buffer (&#8220;isotype control solution&#8221;).</li>
			<li>Split half of the blocked cells from step 1.3.1.2) into an additional polystyrene round bottom tube and add 20 &#181;l of &#8220;staining solution&#8221; in one tube and 20 &#181;l of &#8220;isotype controls solution&#8221; in the other tube. Incubate 30 min on ice.</li>
			<li>Add 3 ml ice-cold FACS buffer and centrifuge at 400 x g for 5 min at 4 &#176;C. Discard supernatant and resuspend the pellet in 300 &#181;l FACS buffer containing 1 &#181;g/ml propidium iodide (PI, for identification of dead cells). Proceed to flow cytometry analysis (see Figure 2A).</li>
		</ol>
		</li>
		<li>Using toluidine blue staining.
		<ol>
			<li>Wash 1 x 105 cells once with PBS by centrifugation at 400 x g for 5 min at room temperature, then aspirate and resuspend cells in 200 &#181;l of PBS.</li>
			<li>Transfer the cell suspension into a prepared cytofunnel attached to a microscope slide and proceed with cyto-centrifugation using a cytocentrifuge (40 x g for 5 min).</li>
			<li>Air dry slides for 10 min and draw a wax circle around cells using a PAP pen. Add 0.1% Toluidine blue solution to cover the cells. Incubate for 1 min. Wash slides in running tap water for 1 min, then air-dry slides for 10 min.</li>
			<li>Coverslip cells using mounting medium. Proceed to light microscope analysis (see Figure 2B)</li>
		</ol>
		</li>
	</ol>
	</li>
</ol>
2. Engraftment of Mast Cell-deficient Mice with BMCMCs.
<ol>
	<li>Ear engraftment by intradermal (i.d.) injection. 
	NOTE: For adoptive transfer of BMCMCs into the ear pinnae of MC-deficient mice, we recommend performing two injections of 1 x 106 cells each (for a total of 2 x 106 cells) per ear pinna. Intradermal engraftment of BMCMCs into the ear pinnae of MC-deficient mice has been used by many investigators in several models, including models of passive cutaneous anaphylaxis (PCA)24,27, host defense against venoms28, and chronic hypersensitivity (CHS) reactions29,30.
	<ol>
		<li>Count and resuspend cells at 4 x 107 BMCMCs/ml (1 x 106 BMCMCs/ 25 &#181;l) in cold DMEM. Transfer BMCMCs solution into a 1 ml syringe equipped with a 30 G needle. Keep on ice until injection.</li>
		<li>Anesthetize 4-6 weeks old MC-deficient mice using isoflurane (2.5% v/v). Check depth of anesthesia by toe pinch, adjust isoflurane if indicated and continue to monitor breathing and toe pinch response throughout the procedure. Apply ophthalmic ointment with a Q-tip to prevent dryness of eyes.</li>
		<li>With the index finger, create vertical pressure on the dorsal face of the ear pinna to expose and stretch the ventral face.</li>
		<li>Perform two 25 &#181;l i.d. injections of BMCMC solution into two different sites of the ventral face of the ear pinna, the first injection in the middle of the ear and the second injection toward the tip of the ear pinna. Wait 4-6 weeks after i.d. engraftment before performing in vivo experiments. 
		Note: In our experience, by that time the number of MCs/mm2 of dermis in the central part of the ear pinna generally is similar to that in the corresponding location in wild type mice, whereas the numbers of MCs/mm2 in the periphery of the ear pinnae are typically substantially lower than those in the corresponding wild type mice27,28. This should be kept in mind when designing experiments with such MC-engrafted mice (e.g., agents with possible effects on MC function should be injected into the central part of the ear pinnae, and the analysis of the effects of such treatments should also focus on that area).</li>
	</ol>
	</li>
	<li>Peritoneal cavity engraftment by intraperitoneal (i.p.) injection. 
	NOTE: Adoptive transfer of BMCMCs into the peritoneal cavity of MC-deficient mice will require one injection of 2 x 106 cells per mouse. Such i.p. injections of BMCMCs into MC-deficient mice have been used by many groups to study the roles of peritoneal MCs in various models, including models of host defense against venoms31 or bacterial sepsis32,33.
	<ol>
		<li>Count appropriate number of cells and resuspend at 1 x 107 BMCMCs/ml (2 x 106 BMCMCs/ 200 &#181;l) in cold DMEM. Transfer BMCMCs solution into a 1 ml syringe equipped with a 25 G needle. Keep on ice until injection.</li>
		<li>Perform 1 injection of 200 &#181;l BMCMCs solution into the peritoneal cavity of 4-6 week old MC-deficient mice. Wait 4-6 weeks after i.p. engraftment before performing in vivo experiments.</li>
	</ol>
	</li>
	<li>Engraftment by intravenous (i.v.) injection. 
	NOTE:Adoptive transfer of BMCMCs by i.v. injection into MC-deficient mice will require one injection of 5 x 106 cells per mouse. Intravenous (i.v.) injections of BMCMCs into MC-deficient mice have been used by many groups to study the roles of MCs in various disease models, including models of bladder infection34, asthma35, lung fibrosis36, and antibody-mediated arthritis37.
	<ol>
		<li>Count appropriate number of cells and resuspend at 2.5 x 107 BMCMCs/ml (5 x 106 BMCMCs/200 &#181;l) in cold DMEM. Transfer BMCMCs solution into a 1 ml syringe equipped with a 30 G needle. Keep on ice until injection.</li>
		<li>Anesthetize 4-6 weeks old MC-deficient mice using isoflurane (2.5% v/v). Check depth of anesthesia by toe pinch, adjust isoflurane if indicated and continue to monitor breathing and toe pinch response throughout the procedure. Apply ophthalmic ointment with a Q-tip to prevent dryness of eyes.</li>
		<li>Perform one injection of 200 &#181;l of BMCMC solution into the tail vein (or, alternatively, the retro-orbital vein) of a MC-deficient mouse. Wait 12 weeks after i.v. engraftment before performing in vivo experiments.</li>
	</ol>
	</li>
</ol>
3. Analysis of Engrafted Mast Cell-deficient Mice.
<ol>
	<li>Ear engraftment analysis.
	<ol>
		<li>At the end of the experiment, euthanize mice by CO2 inhalation followed by cervical dislocation.</li>
		<li>Isolate the ear pinnae and fix in 10% (vol/vol) buffered formalin overnight at 4 &#176;C. Embed fixed ear pinnae in paraffin, cut 4 &#181;m sections of ear pinnae and mount on glass slides.</li>
		<li>Stain the slides with a 0.1% Toluidine blue solution for 1 min at room temperature. Wash slides in tap water for 1 min, then air-dry slides for 10 min at room temperature.</li>
		<li>Coverslip slides using mounting medium, then count the number of engrafted MCs per pinnae sections using a light microscope. Evaluate the engraftment efficiency by comparing the percentage and distribution of MCs in the ear skin of engrafted mice versus wild type mice.</li>
	</ol>
	</li>
	<li>Peritoneal cavity engraftment analysis.
	<ol>
		<li>Evaluation of mast cells number in the peritoneal cavity.
		<ol>
			<li>At the end of the experiment, euthanize mice by CO2 inhalation followed by cervical dislocation. Remove carefully the ventral skin of the mice without breaking the peritoneal cavity.</li>
			<li>Inject 5 ml of cold or room temperature PBS in the peritoneal cavity using a 5 ml syringe equipped with a 25 G needle. Use cold PBS to reduce the risk of activating peritoneal cells (this is very important when evaluating peritoneal MC degranulation or levels of some MC-derived products in the peritoneal lavage fluid). Perform a massage of the abdomen for 20 sec to harvest peritoneal cells.</li>
			<li>Slowly aspirate the peritoneal lavage using a 5 ml syringe equipped with a 22 G needle. Record the volume of aspirated lavage (expect to recover up to 80% of injected volume).</li>
			<li>Transfer peritoneal lavage fluid into a 5 ml polystyrene round bottom tube and centrifuge at 400 x g for 5 min at 4 &#176;C. Aspirate supernatant. Recover the pellet in 400 &#181;l cold PBS.</li>
			<li>Count total number of peritoneal cells using a hemocytometer chamber. Use half of the cell suspension for a flow cytometry analysis (as described in step 1.3.1), to evaluate the percentage and marker expression of engrafted MCs in the peritoneal cavity. Multiply the total number of peritoneal cells by the percentage of MCs to obtain absolute number of peritoneal MCs.</li>
			<li>Perform a cytocentrifugation with the remaining cells as described in step 1.3.2.2. Air dry slides for 10 min at room temperature and draw a wax circle around cells using a PAP pen.</li>
			<li>Cover cells with undiluted May-Gr&#252;nwald Staining solution for 5 min, followed by washing in PBS for 5 min, both at room temperature. Cover cells with Giemsa stain diluted 1:20 with deionized water and incubate 20 min at room temperature. Wash slides 2 times in tap water for 1 min, then air-dry slides.</li>
			<li>Coverslip cells using mounting medium, and calculate the percentage of engrafted MCs using a light microscope (by counting at least 400 total cells). Evaluate the engraftment efficiency by comparing the percentage of MCs in the peritoneal lavage of engrafted mice versus wild type mice.</li>
		</ol>
		</li>
		<li>Evaluation of mast cells in the mesenteric windows.
		<ol>
			<li>Following the peritoneal lavage described in step 3.2.1, cut open the peritoneal membrane to expose the intestinal tract of the mice. Arrange 4 to 5 mesenteric windows per mouse onto a slide.</li>
			<li>Fix the slides for 1 hr in Carnoy solution (3:2:1 vol/vol/vol of ethanol, chloroform, and glacial acetic acid) at room temperature. Air-dry slides and remove the intestine (the fixed mesenteric windows will remain attached to the slides).</li>
			<li>Stain the preparations for 20 min at room temperature with Csaba (Alcian blue/Safranin O) staining solution.
			<ol>
				<li>To make 500 ml of Csaba stain, prepare 500 ml of acetate buffer by mixing 100 ml of 1 M sodium acetate solution with 120 ml of 1 M HCl. Make up to 500 ml with deionized water and adjust pH to 1.42. Then, dissolve 90 mg Safranin [identifies &#8216;mature MCs&#8217; in red], 1.8 g Alcian blue [identifies &#8216;immature MCs&#8217; in blue] and 2.4 g ferric ammonium sulphate NH4Fe(SO4)2 into 500 ml of acetate buffer.</li>
			</ol>
			</li>
			<li>Coverslip slides using mounting medium, then count the number of engrafted MCs per mesenteric window using a light microscope. Evaluate the engraftment efficiency by comparing the percentage and distribution of MCs in the mesenteric windows of engrafted mice versus wild type mice.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>I.v. engraftment analysis.
	<ol>
		<li>At the end of the experiment, euthanize mice by CO2 inhalation followed by cervical dislocation, and harvest tissue of interest (e.g. lung, skin or spleen) and fix overnight in 10% (vol/vol) buffered formalin at 4 &#176;C.</li>
		<li>Embed fixed tissues in paraffin, cut 4 &#181;m sections, and mount on glass slides. Stain the slides with a 0.1% Toluidine blue solution for 1 min at room temperature. Wash slides in tap water for 1 min, then air-dry slides for 10 min.</li>
		<li>Coverslip slides using mounting medium and evaluate number and distribution of engrafted MCs per tissue sections using a light microscope.</li>
	</ol>
	</li>
</ol>

The authors have nothing to disclose.

Almost 30 years after its initial description38, the &#8216;mast cell knock-in&#8217; approach continues to provide valuable information about what MCs can do or can&#8217;t do in vivo. The functions of MCs were long thought to be limited to their role in allergy. Data generated using the &#8216;mast cell knock-in&#8217; approach have changed this view, by providing evidence that MCs can, among other functions, play critical roles in host defense against certain pathogens4,39</s...

Mast cells (MCs) are hematopoietic cells that arise from pluripotent bone marrow progenitors1-3. Following bone marrow egression, MCs progenitors migrate into various tissues where they develop into mature MCs under the influence of local growth factors1-3. Tissue-resident MCs are strategically located at host-environment interfaces, such as the skin, the airways and the gastrointestinal tract, where they behave as a first line of defense against external insults3-6. MCs are often sub-classified based on their &#8220;baseline&#8221; phenotypic characteristics and their anatomic locations. In mice, two types of MCs have been described: &#8220;connective tissue-type&#8221; MCs (CTMCs) and mucosal MCs (MMCs)1-3,7,8. CTMCs are often located around venules and near nerve fibers, and reside in serosal cavities, while MMCs occupy intraepithelial locations in the gut and respiratory mucosa1-3.
Numerous methodologies have been applied to study biological functions of MCs9-13. Many groups have focused on in vitro approaches using either cell lines (such as the human MC lines HMC114 or LAD215,16), in vitro derived MCs (such as human peripheral blood-derived MCs17, or mouse bone marrow-derived cultured MCs [BMCMCs]18, fetal skin-derived cultured MCs [FSCMCs]19 and peritoneal cell-derived MCs [PCMCs]20) or ex vivo isolated MCs from different anatomical sites. All these models are widely used to study molecular details of MC biology, such as signaling pathways involved in MC activation. However, an important aspect of MCs biology is that their phenotypic and functional characteristics (e.g., cytoplasmic granule protease content or response to different stimuli) can be modulated by anatomical location and microenvironment2,7. Since the exact mixture of such factors that are encountered in vivo may be difficult to reproduce in vitro, we favor using in vivo approaches to gain insights into MCs functions9.
Several mouse strains with genetic MC deficiency exist, such as the widely used WBB6F1-Kit W/W-v or C57BL/6-Kit W-sh/W-sh mice. These mice lack expression and/or activity of KIT (CD117), the receptor for the main MC growth factor stem cell factor (SCF)21,22. As a result, these mice have a profound MC deficiency but also have additional phenotypic abnormalities related to their c-kit mutations (in the WBB6F1-Kit W/W-v mice) or to the effects of the large chromosomal inversion that results in reduced c-kit expression (in the C57BL/6-Kit W-sh/W-sh mice)9,10,12,23. More recently, several strains of mice with c-kit-independent constitutive MC deficiency have been reported24-26. All these mice and some additional new types of inducible MC-deficient mice have been recently reviewed in detail9,10,13.
Here, we describe methods for the generation of mouse bone marrow-derived cultured MCs (BMCMCs), their adoptive transfer into MC-deficient mice, and the analysis of the numbers and distribution of adoptively transferred MCs at different anatomical sites. This so-called &#8216;mast cell knock-in&#8217; method can be used 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.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>1% Antibiotic-Antimycotic Solution</td>
			<td>Corning cellgro</td>
			<td>30-004-Cl</td>
			<td></td>
		</tr>
		<tr>
			<td>3 ml Syringe</td>
			<td>Falcon</td>
			<td>309656</td>
			<td></td>
		</tr>
		<tr>
			<td>35 mm x 10 mm Dish</td>
			<td>Corning cellgro</td>
			<td>430588</td>
			<td></td>
		</tr>
		<tr>
			<td>5 ml Polystyrene Round Bottom Tube</td>
			<td>Falcon</td>
			<td>352058</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetic Acid Glacial</td>
			<td>Fisher Scientific</td>
			<td>A35-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Alcian Blue 8GX</td>
			<td>Rowley Biochemical Danver</td>
			<td>33864-99-2</td>
			<td></td>
		</tr>
		<tr>
			<td>Allegra 6R Centrifuge</td>
			<td>Beckman</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-mouse CD16/32 (clone 93) Purified</td>
			<td>eBioscience</td>
			<td>14-0161-81</td>
			<td></td>
		</tr>
		<tr>
			<td>2-Mercaptoethanol</td>
			<td>Sigma Aldrich</td>
			<td>M7522</td>
			<td></td>
		</tr>
		<tr>
			<td>BD 1 ml TB Syringe</td>
			<td>BD Syringe</td>
			<td>309659</td>
			<td></td>
		</tr>
		<tr>
			<td>BD 22G x1 (0.7 mm x 25 mm) Needles</td>
			<td>BD Precision Glide Needle</td>
			<td>205155</td>
			<td></td>
		</tr>
		<tr>
			<td>BD 25G 5/8 Needles</td>
			<td>BD Syringe</td>
			<td>305122</td>
			<td></td>
		</tr>
		<tr>
			<td>BD 30G x1/2 Needles</td>
			<td>BD Precision Glide</td>
			<td>305106</td>
			<td></td>
		</tr>
		<tr>
			<td>Blue MAX Jr, 15 ml Polypropylene Conical Tube</td>
			<td>Falcon</td>
			<td>352097</td>
			<td></td>
		</tr>
		<tr>
			<td>Chloroform</td>
			<td>Fisher Scientific</td>
			<td>C298-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Cytoseal 60 Mounting Medium</td>
			<td>Richard-Allan Scientific</td>
			<td>8310-4</td>
			<td></td>
		</tr>
		<tr>
			<td>Cytospin3</td>
			<td>Shandon</td>
			<td>NA</td>
			<td></td>
		</tr>
		<tr>
			<td>DakoCytomation pen</td>
			<td>Dako</td>
			<td>S2002</td>
			<td></td>
		</tr>
		<tr>
			<td>Dulbecco Modified Eagle Medium (DMEM) 1x</td>
			<td>Corning cellgro</td>
			<td>15-013-CM</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>Sigma Aldrich</td>
			<td>E 7023-500ml</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum Heat Inactivated</td>
			<td>Sigma Aldrich</td>
			<td>F4135-500ml</td>
			<td></td>
		</tr>
		<tr>
			<td>FITC Conjugated IgG2b K Rat Isotype Control</td>
			<td>eBioscience</td>
			<td>14-4031-82</td>
			<td></td>
		</tr>
		<tr>
			<td>Fluorescein Isotiocyanate (FITC) Conjugated Anti-mouse KIT (CD117; clone 2B8)</td>
			<td>eBioscience</td>
			<td>11-1171-82</td>
			<td></td>
		</tr>
		<tr>
			<td>Formaldehyde</td>
			<td>Fisher Scientific</td>
			<td>F79-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Giemsa Stain Modified</td>
			<td>Sigma Aldrich</td>
			<td>GS-1L</td>
			<td></td>
		</tr>
		<tr>
			<td>Isothesia</td>
			<td>Henry Schein Animal Health</td>
			<td>29405</td>
			<td></td>
		</tr>
		<tr>
			<td>May-Grunwald Stain</td>
			<td>Sigma Aldrich</td>
			<td>MG-1L</td>
			<td></td>
		</tr>
		<tr>
			<td>Multiwell 6 well plates</td>
			<td>Falcon</td>
			<td>35 3046</td>
			<td></td>
		</tr>
		<tr>
			<td>Olympus BX60 Microscope</td>
			<td>Olympus</td>
			<td>NA</td>
			<td></td>
		</tr>
		<tr>
			<td>Paraplast Plus Tissue Embedding Medium</td>
			<td>Fisher Brand</td>
			<td>23-021-400</td>
			<td></td>
		</tr>
		<tr>
			<td>PE Conjugated IgG Armenian Hamster Isotype Control</td>
			<td>eBioscience</td>
			<td>12-4888-81</td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphate-Buffered-Saline (PBS) 1x</td>
			<td>Corning cellgro</td>
			<td>21-040-CV</td>
			<td></td>
		</tr>
		<tr>
			<td>Phycoerythrin (PE) Conjugated Anti-mouse FceRIa (clone MAR-1)</td>
			<td>eBioscience</td>
			<td>12-5898-82</td>
			<td></td>
		</tr>
		<tr>
			<td>Propidium Iodide Staining Solution</td>
			<td>eBioscience</td>
			<td>00-6990-50</td>
			<td></td>
		</tr>
		<tr>
			<td>Recombinant Mouse IL-3</td>
			<td>Peprotech</td>
			<td>213-13</td>
			<td></td>
		</tr>
		<tr>
			<td>Safranin-o Certified</td>
			<td>Sigma Aldrich</td>
			<td>S8884</td>
			<td></td>
		</tr>
		<tr>
			<td>Tissue culture flasks T25 25 cm2</td>
			<td>Beckton Dickinson</td>
			<td>353109</td>
			<td></td>
		</tr>
		<tr>
			<td>Tissue culture flasks T75 75 cm2</td>
			<td>Beckton Dickinson</td>
			<td>353110</td>
			<td></td>
		</tr>
		<tr>
			<td>Toluidine Blue 1 % Aqueous</td>
			<td>LabChem-Inc</td>
			<td>LC26165-2</td>
			<td></td>
		</tr>
		<tr>
			<td>Recombinant Mouse SCF</td>
			<td>Peprotech</td>
			<td>250-03</td>
			<td></td>
		</tr>
	</tbody>
</table>

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.

An overview of the &#8216;mast cell knock-in&#8217; approach is shown in Figure 1, and includes the generation of BMCMCs, the number of cells that should be engrafted i.p., i.d. or i.v. into MC-deficient mice (the number can be varied if indicated based on the experimental design) and the interval between engraftment and experiment depending on the injection site (this interval also can vary, if indicated; e.g., the content of stored mediators in MC cytoplasmic granules increases steadi...

Watch this Scientific Journal Video about Analyzing the Functions of Mast Cells In Vivo Using 'Mast Cell Knock-in' Mice at JoVE.com

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.

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 ...

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Research

JoVE Journal

Immunology and Infection

10.2K Views.  Stanford University School of Medicine. 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.

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

Following Cell-fate in E. coli After Infection by Phage Lambda

The system comprising bacteriophage (phage) lambda and the bacterium E. coli has long served as a paradigm for cell-fate determination1,2. Following the simultaneous infection of the cell by a number of phages, one of two pathways is chosen: lytic (virulent) or lysogenic (dormant)3,4. We recently developed a method for fluorescently labeling individual phages, and were able to examine the post-infection decision in real-time under the microscope, at the level of individual phages and cells5. Here, we describe the full procedure for performing the infection experiments described in our earlier work5. This includes the creation of fluorescent phages, infection of the cells, imaging under the microscope and data analysis. The fluorescent phage is a "hybrid", co-expressing wild- type and YFP-fusion versions of the capsid gpD protein. A crude phage lysate is first obtained by inducing a lysogen of the gpD-EYFP (Enhanced Yellow Fluorescent Protein) phage, harboring a plasmid expressing wild type gpD. A series of purification steps are then performed, followed by DAPI-labeling and imaging under the microscope. This is done in order to verify the uniformity, DNA packaging efficiency, fluorescence signal and structural stability of the phage stock. The initial adsorption of phages to bacteria is performed on ice, then followed by a short incubation at 35&deg;C to trigger viral DNA injection6. The phage/bacteria mixture is then moved to the surface of a thin nutrient agar slab, covered with a coverslip and imaged under an epifluorescence microscope. The post-infection process is followed for 4 hr, at 10 min interval. Multiple stage positions are tracked such that ~100 cell infections can be traced in a single experiment. At each position and time point, images are acquired in the phase-contrast and red and green fluorescent channels. The phase-contrast image is used later for automated cell recognition while the fluorescent channels are used to characterize the infection outcome: production of new fluorescent phages (green) followed by cell lysis, or expression of lysogeny factors (red) followed by resumed cell growth and division. The acquired time-lapse movies are processed using a combination of manual and automated methods. Data analysis results in the identification of infection parameters for each infection event (e.g. number and positions of infecting phages) as well as infection outcome (lysis/lysogeny). Additional parameters can be extracted if desired.

Following Cell-fate in E. coli After Infection by Phage Lambda

This article describes the procedure for preparing a fluorescently-labeled version of bacteriophage lambda, infection of E. coli bacteria, following the infection outcome under the microscope, and analysis of infection results.

The system comprising bacteriophage (phage) lambda and the bacterium E. coli has long served as a paradigm for cell-fate determination1,2. Following the ...

Induction of Graft-versus-host Disease and In Vivo T Cell Monitoring Using an MHC-matched Murine Model

Graft-versus-host disease (GVHD) is the limiting barrier to the broad use of bone marrow transplant as a curative therapy for a variety of hematological deficiencies. GVHD is caused by mature alloreactive T cells present in the bone marrow graft that are infused into the recipient and cause damage to host organs. However, in mice, T cells must be added to the bone marrow inoculum to cause GVHD. Although extensive work has been done to characterize T cell responses post transplant, bioluminescent imaging technology is a non-invasive method to monitor T cell trafficking patterns in vivo. 
Following lethal irradiation, recipient mice are transplanted with bone marrow cells and splenocytes from donor mice. T cell subsets from L2G85.B6 (transgenic mice that constitutively express luciferase) are included in the transplant. By only transplanting certain T cell subsets, one is able to track specific T cell subsets in vivo, and based on their location, develop hypotheses regarding the role of specific T cell subsets in promoting GVHD at various time points. At predetermined intervals post transplant, recipient mice are imaged using a Xenogen IVIS CCD camera. Light intensity can be quantified using Living Image software to generate a pseudo-color image based on photon intensity (red = high intensity, violet = low intensity). 
Between 4-7 days post transplant, recipient mice begin to show clinical signs of GVHD. Cooke et al.1 developed a scoring system to quantitate disease progression based on the recipient mice fur texture, skin integrity, activity, weight loss, and posture. Mice are scored daily, and euthanized when they become moribund. Recipient mice generally become moribund 20-30 days post transplant. 
Murine models are valuable tools for studying the immunology of GVHD. Selectively transplanting particular T cell subsets allows for careful identification of the roles each subset plays. Non-invasively tracking T cell responses in vivo adds another layer of value to murine GVHD models.

Induction of Graft-versus-host Disease and In Vivo T Cell Monitoring Using an MHC-matched Murine Model

Murine bone marrow transplantation is a widely used technique to study immunological mechanisms governing graft-versus-host disease in humans. The ability to monitor T cell trafficking patterns in vivo allows for detailed analysis of the development and perpetuation of T cell responses during graft-versus-host disease.

Graft-versus-host disease (GVHD) is the limiting barrier to the broad use of bone marrow transplant as a curative therapy for a variety of hematological ...

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 ...

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.

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 ...

Assessing Retinal Microglial Phagocytic Function In Vivo Using a Flow Cytometry-based Assay

Microglia are the tissue resident macrophages of the central nervous system (CNS) and they perform a variety of functions that support CNS homeostasis, including phagocytosis of damaged synapses or cells, debris, and/or invading pathogens. Impaired phagocytic function has been implicated in the pathogenesis of diseases such as Alzheimer's and age-related macular degeneration, where amyloid-&#946; plaque and drusen accumulate, respectively. Despite its importance, microglial phagocytosis has been challenging to assess in vivo. Here, we describe a simple, yet robust, technique for precisely monitoring and quantifying the in vivo phagocytic potential of retinal microglia. Previous methods have relied on immunohistochemical staining and imaging techniques. Our method uses flow cytometry to measure microglial uptake of fluorescently labeled particles after intravitreal delivery to the eye in live rodents. This method replaces conventional practices that involve laborious tissue sectioning, immunostaining, and imaging, allowing for more precise quantification of microglia phagocytic function in just under six hours. This procedure can also be adapted to test how various compounds alter microglial phagocytosis in physiological settings. While this technique was developed in the eye, its use is not limited to vision research.

Assessing Retinal Microglial Phagocytic Function In Vivo Using a Flow Cytometry-based Assay

Microglial phagocytosis is critical for the maintenance of tissue homeostasis and inadequate phagocytic function has been implicated in pathology. However, assessing microglia function in vivo is technically challenging. We have developed a simple but robust technique for precisely monitoring and quantifying the phagocytic potential of microglia in a physiological setting.

Microglia are the tissue resident macrophages of the central nervous system (CNS) and they perform a variety of functions that support CNS homeostasis, ...

In Vivo Assay for Detection of Antigen-specific T-cell Cytolytic Function Using a Vaccination Model

Current methodologies for antigen-specific killing are limited to in vitro use or utilized in infectious disease models. However, there is not a protocol specifically intended to measure antigen-specific killing without an infection. This protocol is designed and describes methods to overcome these limitations by allowing for the detection of antigen-specific killing of a target cell by CD8+ T cells in vivo. This is accomplished by merging a vaccination model with a traditional CFSE-labeled target killing assay. This combination allows the researcher to assess the antigen-specific CTL potential directly and quickly as the assay is not dependent upon tumor growth or infection. In addition, the readout is based on flow cytometry and so should be readily accessible to most researchers. The major limitation of the study is identifying the timeline in vivo that is appropriate to the hypothesis being tested. Variations in antigen strength and mutations in the T cells that may result in differential cytolytic function need to be carefully assessed to determine the optimal time for cell harvest and assessment. The appropriate concentration of peptide for vaccination has been optimized for hgp10025-33 and OVA257-264, but further validation would be needed for other peptides that may be more appropriate to a given study. Overall, this protocol allows a quick assessment of killing function in vivo and can be adapted to any given antigen.

In Vivo Assay for Detection of Antigen-specific T-cell Cytolytic Function Using a Vaccination Model

The goal of this protocol is to allow for detection of in vivo antigen-specific killing of a target cell in a murine model.

Current methodologies for antigen-specific killing are limited to in vitro use or utilized in infectious disease models. However, there is not a protocol ...

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 ...

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.

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

Generation of Knock-out Primary and Expanded Human NK Cells Using Cas9 Ribonucleoproteins

CRISPR/Cas9 technology is accelerating genome engineering in many cell types, but so far, gene delivery and stable gene modification have been challenging in primary NK cells. For example, transgene delivery using lentiviral or retroviral transduction resulted in a limited yield of genetically-engineered NK cells due to substantial procedure-associated NK cell apoptosis. We describe here a DNA-free method for genome editing of human primary and expanded NK cells using Cas9 ribonucleoprotein complexes (Cas9/RNPs). This method allowed efficient knockout of the TGFBR2 and HPRT1 genes in NK cells. RT-PCR data showed a significant decrease in gene expression level, and a cytotoxicity assay of a representative cell product suggested that the RNP-modified NK cells became less sensitive to TGF&#946;. Genetically modified cells could be expanded post-electroporation by stimulation with irradiated mbIL21-expressing feeder cells.

Here, we present a protocol to genetically modify primary or expanded human natural killer (NK) cells using Cas9 Ribonucleoproteins (Cas9/RNPs). By using this protocol, we generated human NK cells deficient for transforming growth factor&#8211;b receptor 2 (TGFBR2) and hypoxanthine phosphoribosyltransferase 1 (HPRT1).

CRISPR/Cas9 technology is accelerating genome engineering in many cell types, but so far, gene delivery and stable gene modification have been challenging ...

Evaluation of T Follicular Helper Cells and Germinal Center Response During Influenza A Virus Infection in Mice

T Follicular Helper (Tfh) cells are an independent CD4+&#160;T cell subset specialized in providing help for germinal center (GC) development and generation of high-affinity antibodies. In influenza virus infection, robust Tfh and GC B cell responses are induced to facilitate effective virus eradication, which confers a qualified mouse model for Tfh-associated study. In this paper, we described protocols in detection of basic Tfh-associated immune response during influenza virus infection in mice. These protocols include: intranasal inoculation of influenza virus; flow cytometry staining and analysis of polyclonal and antigen-specific Tfh cells, GC B cells and plasma cells; immunofluorescence detection of GCs; enzyme-linked immunosorbent assay (ELISA) of influenza virus-specific antibody in serum. These assays basically quantify the differentiation and function of Tfh cells in influenza virus infection, thus providing help for studies in elucidating differentiation mechanism and manipulation strategy.

This paper describes protocols of evaluating Tfh and GC B response in mouse model of influenza virus infection.