We are grateful to the Martin laboratory for helpful discussions. This publication is supported by a grant from the Canadian Institute of Health Research (MOP-89783). A.M. is supported by a Canada Research Chair Tier II Award.

Step I: Isolation of splenic B cells via magnetic enrichment
<ol>
 <li>Experimental mice should be aged 8-12 weeks to ensure full maturation of the immune system.</li>
 <li>Euthanize the mouse by cervical dislocation and soak in 70% ethanol. Surgically remove the spleen by making an incision through the skin and muscle of the left hypochondrium of the abdomen and cut it into three large pieces in phosphate buffered saline (PBS). Ensure all tools and reagents are sterile.</li>
 <li>Using the rubber end of a 1 mL syringe plunger, gently mash the spleen through a 70 &mu;m cell strainer into PBS. Be sure to use a pushing motion rather than a grinding motion as grinding may lead to rupture of larger (i.e. proliferating) cells.</li>
 <li>Spin down the cells at no more than 350 g for 5 minutes and resuspend the pellet in PBS. Count the resuspended cells using a hemocytometer.</li>
 <li>Prepare a suspension of 1x108 cells/mL in PBS with 5% normal rat serum in a sterile 5 mL polystyrene tube with a cap (maximum volume of 2 mL per tube).</li>
 <li>Add 50 &mu;L of EasySep Negative Selection Mouse B Cell Enrichment cocktail for every mL of cells. Pipette the mixture, cap the tubes, and place in the fridge for 15 minutes.</li>
 <li>Add 100 &mu;L EasySep Biotin Selection Cocktail for every mL of cells. Pipette the mixture, cap the tubes, and place in the fridge for 15 minutes.</li>
 <li>Add 100 &mu;L of EasySep Magnetic Nanoparticles (ensure nanoparticles are mixed well and the solution is homogenous) for every mL of cells. Pipette the mixture, cap the tubes, and place in the fridge for 5 minutes.</li>
 <li>Top the solution to 2.5mL with PBS and place in an EasySep magnet for 5 minutes. Invert the magnet and tube and pour quickly into a new polystyrene tube. Do not shake the tube as negatively selected cells will be magnetically bound to the tube walls.</li>
 <li>To further increase the purity of the cell suspension, the tube may be reinserted into the magnet for an additional 5 minutes and poured into a new tube. This may reduce overall cell recovery.</li>
 <li>B cell purity can be assessed by flow cytometric analysis of B cell surface markers. Following enrichment, we consistently see a purity of &gt;95% B220 positive cells.</li>
</ol>
Step II: CFSE cell staining
<ol>
 <li>Resuspend the isolated cells in warm PBS supplemented with 0.1% bovine serum albumin at a final concentration of 1 x 106 cells per mL.</li>
 <li>Prepare a 5mM stock solution of CFSE (diluted in sterile dimethyl sulfoxide) and add 2&mu;L for every mL of cells in the tube. The final concentration of 10&mu;M is optimal for the staining of primary B cells.</li>
 <li>Incubate at 37&deg;C for 10 minutes in the dark (note: CFSE is light sensitive and should be kept in the dark when possible).</li>
 <li>Quench the stain by adding an equal volume of bovine calf serum to your cells and incubating on ice for 5 minutes.</li>
 <li>Wash the cells by topping up the tubes with culture medium (see step III for recipe) and centrifuging at 350 g. Note that at least 5 times the volume equivalent of media must be added to counteract the viscosity of the bovine calf serum and for the cells to produce a pellet.</li>
 <li>Wash the cells twice more in culture medium. The cells are now ready for stimulation.</li>
</ol>
Step III: Cell stimulation with LPS
<ol>
 <li>Prepare your in vitro B cell culture medium by supplementing RPMI 1640 with 10% fetal calf serum and 50 &mu;M &beta;-mercaptoethanol/. </li>
 <li>Prepare your stimulation medium by adding LPS at a final concentration of 50&mu;g/mL. Aliquot 125 &mu;L of the stimulation medium into each well of a flat bottom 96-well tissue culture plate.</li>
 <li>Prepare your CFSE-stained B cells in culture medium without LPS at a final concentration of 3.2 x 106 cells/mL. Add 125 &mu;L of the cell suspension to the wells containing your stimulation medium and mix by pipetting gently.</li>
 <li>Each well now contains 4 x 105 cells in a final LPS concentration of 25 &mu;g/mL. This provides optimal levels of cell proliferation and class switching, although alterations to these values may be made as desired.</li>
 <li>Incubate the cells at 37&deg;C and 5% CO2 for 72 to 96 hours. After 48 hours, clusters of large proliferating B cells will be clearly visible under a microscope.</li>
</ol>
Step IV: Flow cytometric analysis of class switching
<ol>
 <li>When you are ready to look at class switching, remove your cells from their culture conditions and wash them twice in 1 mL of staining buffer (PBS with 2% bovine calf serum).</li>
 <li>To prevent non-specific antibody staining of your cells, pellet the cells by spinning them down at 350 g and incubate them in 100&mu;L of staining buffer with 5% normal mouse serum and 1&mu;g of FcBlock per106 cells for 15 minutes on ice. Cell blocking should be performed on ice.</li>
 <li>Without washing your cells, add 1&mu;g per 106 cells of a fluorescently tagged anti mouse IgG3 antibody and allow the cells to stain for 30 minutes on ice. </li>
 <li>Wash the cells twice by centrifugation and resuspend in 200-300 &mu;L of staining buffer. The cells are now ready for assessment by flow cytometry.</li>
 <li>CFSE is optimally excited at 492 nm (by an argon-ion laser) and emits at 517 nm. The excitation and emission spectrum of the IgG3 antibody is dependent on its conjugate fluorescent dye.</li>
</ol>
Representative Results
Following magnetic enrichment, the cell suspension should look like a homogenous population of indistinguishable small circular cells (Figure 1A). After 48-72 hours of stimulation, isolated clusters of enlarged proliferating cells will be clearly visible (Figure 1B). A large proportion of the non-proliferating cells will appear small and granular as they undergo apoptosis.
CSR can normally be detected at the highest levels between 72 and 96 hours after stimulation before most of the cells begin to die 7. At this stage, the cells should have undergone a number of cell divisions with switched cells appearing in the later daughter cell population. A representative flow cytometric plot of CFSE dilution and surface expression of IgG3 after 96 hours of LPS stimulation can be seen in Figure 2.
Table 1. Isotype switching cocktails. Note: Stimulant concentration values are recommendations only. Titrations may be necessary.
<table border="1">
 <tbody>
 <tr>
 <td>Desired Isotype</td>
 <td>Stimulation Cocktail</td>
 </tr>
 <tr>
 <td>IgG1and IgE</td>
 <td>LPS (25&mu;g/mL) and IL-4 (10 ng/mL)</td>
 </tr>
 <tr>
 <td>IgG1and IgE</td>
 <td>Anti-CD40 (10&mu;g/mL) and IL-4 (10 ng/mL)</td>
 </tr>
 <tr>
 <td>IgG2a</td>
 <td>LPS (25&mu;g/mL) and IFN-&gamma;(10 ng/mL)</td>
 </tr>
 <tr>
 <td>IgG2b and IgG3</td>
 <td>LPS (25&mu;g/mL)</td>
 </tr>
 <tr>
 <td>IgA</td>
 <td>LPS (25&mu;g/mL), TGF-&beta;(2 ng/mL) and IL-5 (1.5 ng/mL)</td>
 </tr>
 </tbody>
</table>
<img src="/files/ftp_upload/2130/2130fig1.jpg" alt="Figure 1" /> 
 Figure 1. Isolation and LPS stimulation of splenic B cells. (a) Magnetically enriched splenic B cells before LPS stimulation. (b) 48 hours after stimulation with 25 &mu;g/mL of LPS. Proliferating cells are seen as clusters in a background of blasting and apoptotic cells.
<img src="/files/ftp_upload/2130/2130fig2.jpg" alt="Figure 2" /> 
 Figure 2. Proliferation and class switch recombination after 96 hours. (a) CFSE dilution for LPS stimulated cells after 96 hours in culture. Each independent peak represents a dilution in CFSE fluorescence corresponding to an independent cell division. (b) IgG3 expression showing the emergence of an IgG3 positive population following several rounds of cell division.

<ol>
	<li>Hodgkin, P. D., Lee, J. H., Lyons, A. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=B+cell+differentiation+and+isotype+switching+is+related+to+division+cycle+number.">B cell differentiation and isotype switching is related to division cycle number.</a> J Exp Med. 184, 277-281 (1996).</li><li>McCall, M. N., Hodgkin, P. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Switch+recombination+and+germ-line+transcription+are+division-regulated+events+in+B+lymphocytes.">Switch recombination and germ-line transcription are division-regulated events in B lymphocytes.</a> Biochim Biophys Acta. 1447, 43-50 (1999).</li><li>Manis, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=53BP1+links+DNA+damage-response+pathways+to+immunoglobulin+heavy+chain+class-switch+recombination.">53BP1 links DNA damage-response pathways to immunoglobulin heavy chain class-switch recombination.</a> Nat Immunol. 5, 481-487 (2004).</li><li>de Yebenes, V. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=miR-181b+negatively+regulates+activation-induced+cytidine+deaminase+in+B+cells.">miR-181b negatively regulates activation-induced cytidine deaminase in B cells.</a> J Exp Med. 205, 2199-2206 (2008).</li><li>McBride, K. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regulation+of+class+switch+recombination+and+somatic+mutation+by+AID+phosphorylation.">Regulation of class switch recombination and somatic mutation by AID phosphorylation.</a> J Exp Med. 205, 2585-2594 (2008).</li><li>Ramachandran, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+RNF8/RNF168+ubiquitin+ligase+cascade+facilitates+class+switch+recombination.">The RNF8/RNF168 ubiquitin ligase cascade facilitates class switch recombination.</a> Proc Natl Acad Sci U S A. 107, 809-8014 (2010).</li><li>Zaheen, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=AID+constrains+germinal+center+size+by+rendering+B+cells+susceptible+to+apoptosis.">AID constrains germinal center size by rendering B cells susceptible to apoptosis.</a> Blood. 114, 547-554 (2009).</li><li>Chaudhuri, J., Alt, F. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Class-switch+recombination:+interplay+of+transcription,+DNA+deamination+and+DNA+repair.">Class-switch recombination: interplay of transcription, DNA deamination and DNA repair.</a> Nat Rev Immunol. 4, 541-552 (2004).</li><li>Kaminski, D. A., Stavnezer, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stimuli+that+enhance+IgA+class+switching+increase+histone+3+acetylation+at+S+alpha,+but+poorly+stimulate+sequential+switching+from+IgG2b.">Stimuli that enhance IgA class switching increase histone 3 acetylation at S alpha, but poorly stimulate sequential switching from IgG2b.</a> Eur J Immunol. 37, 240-251 (2007).</li><li>Kaminski, D. A., Stavnezer, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Antibody+class+switching+differs+among+SJL,+C57BL/6+and+129+mice.">Antibody class switching differs among SJL, C57BL/6 and 129 mice.</a> Int Immunol. 19, 545-556 (2007).</li></ol>

No conflicts of interest declared.

The protocol outlined above provides a standard assay to analyze AID expression and function during the class switching of primary murine B cells. This protocol uses bacterial LPS to induce switching from IgM to IgG3, although modifications to the stimulation media can be made to induce switching to other isotypes (summarized in Table 1 8, 9).
We have noted that, for as yet unknown reasons, fetal calf serum can affect the level of class switching observed in vitro. It is crucial th...

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		<div>
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		<thead>
		<tr>
		<th>Material Name</th>
		<th>Type</th>
		<th>Company</th>
		<th>Catalogue Number</th>
		<th>Comment</th>
		</tr>
		</thead>
		<tbody>
		
<tr>
<td>Phosphate Buffered Saline</td>
<td>&nbsp;</td>
<td>Gibco</td>
<td>14190</td>
<td>&nbsp;</td>
<tr>
<td>EasySep Mouse B Cell Enrichment Kit</td>
<td>&nbsp;</td>
<td>Stemcell Technologies</td>
<td>19754</td>
<td>&nbsp;</td>
<tr>
<td>Polystyrene tubes</td>
<td>&nbsp;</td>
<td>Becton Dickinson Falcon</td>
<td>352058</td>
<td>&nbsp;</td>
<tr>
<td>Bovine Serum Albumin</td>
<td>&nbsp;</td>
<td>Sigma Aldrich</td>
<td>A7030</td>
<td>&nbsp;</td>
<tr>
<td>CellTrace CFSE Cell Proliferation Kit</td>
<td>&nbsp;</td>
<td>Invitrogen</td>
<td>C34554</td>
<td>&nbsp;</td>
<tr>
<td>Bovine Calf Serum</td>
<td>&nbsp;</td>
<td>HyClone</td>
<td>SH30072.03</td>
<td>&nbsp;</td>
<tr>
<td>RPMI 1640 Culture Medium</td>
<td>&nbsp;</td>
<td>Gibco</td>
<td>11875</td>
<td>&nbsp;</td>
<tr>
<td>Lipopolysaccharides from Escherichia coli</td>
<td>&nbsp;</td>
<td>Sigma Aldrich</td>
<td>L6529</td>
<td>&nbsp;</td>
<tr>
<td>&beta;-mercaptoethanol</td>
<td>&nbsp;</td>
<td>Gibco</td>
<td>21985</td>
<td>&nbsp;</td>
<tr>
<td>Fetal Bovine Serum</td>
<td>&nbsp;</td>
<td>HyClone</td>
<td>SH30396.03</td>
<td>&nbsp;</td>
<tr>
<td>Normal Mouse Serum</td>
<td>&nbsp;</td>
<td>Jackson ImmunoResearch</td>
<td>011-000</td>
<td>&nbsp;</td>
<tr>
<td>Purified Rat Anti-Mouse CD16/CD32 (Mouse BD Fc Block)</td>
<td>&nbsp;</td>
<td>Becton Dickinson Pharmingen</td>
<td>553141</td>
<td>&nbsp;</td>
<tr>
<td>Rat Anti-Mouse IgG3</td>
<td>&nbsp;</td>
<td>Becton Dickinson Pharmingen</td>
<td>553401</td>
<td>&nbsp;</td>		</tbody>
		</table>
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induction and assessment of class switch recombination in purified murine b cells

Humoral immunity is the branch of the immune system maintained by B cells and mediated through the secretion of antibodies. Upon B cell activation, the immunoglobulin locus undergoes a series of genetic modifications to alter the binding capacity and effector function of secreted antibodies. This process is highlighted by a genomic recombination event known as class switch recombination (CSR) in which the default IgM antibody isotype is substituted for one of IgG, IgA, or IgE. Each isotype possesses distinct effector functions thereby making CSR crucial to the maintenance of immunity. Diversification of the immunoglobulin locus is mediated by the enzyme activation-induced cytidine deaminase (AID). A schematic video describing this process in detail is available online (http://video.med.utoronto.ca/videoprojects/immunology/aam.html). AID's activity and the CSR pathway are commonly studied in the assessment of B cell function and humoral immunity in mice. The protocol outlined in this report presents a method of B cell isolation from murine spleens and subsequent stimulation with bacterial lipopolysaccharide (LPS) to induce class switching to IgG3 (for other antibody isotypes see Table 1). In addition, the fluorescent cell staining dye Carboxyfluorescein succinimidyl ester (CFSE) is used to monitor cell division of stimulated cells, a process crucial to isotype switching 1, 2. The regulation of AID and the mechanism by which CSR occurs are still unclear and thus in vitro class switch assays provide a reliable method for testing these processes in various mouse models. These assays have been previously used in the context of gene deficiency using knockout mice 3. Furthermore, in vitro switching of B cells can be preceded by viral transduction to modulate gene expression by RNA knockdown or transgene expression 4-6. The data from these types of experiments have impacted our understanding of AID activity, resolution of the CSR reaction, and antibody-mediated immunity in the mouse.

Watch this Scientific Journal Video about Induction and Assessment of Class Switch Recombination in Purified Murine B Cells at JoVE.com

Induction and Assessment of Class Switch Recombination in Purified Murine B Cells

Following antigen exposure, subpopulations of activated B cells undergo a process known as class switch recombination (CSR) to produce antibody isotypes with distinct effector functions. The protocol outlined in this report explains how CSR can be induced and analyzed in vitro for the purposes of studying B cell function.

Humoral immunity is the branch of the immune system maintained by B cells and mediated through the secretion of antibodies. Upon B cell activation, the ...

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Immunology and Infection

18.1K Views.  University of Toronto. Following antigen exposure, subpopulations of activated B cells undergo a process known as class switch recombination (CSR) to produce antibody isotypes with distinct effector functions. The protocol outlined in this report explains how CSR can be induced and analyzed in vitro for the purposes of studying B cell function.

Video: Induction and Assessment of Class Switch Recombination in Purified Murine B Cells

Murine Model of CD40-activation of B cells

Research on B cells has shown that CD40 activation improves their antigen presentation capacity. When stimulated with interleukin-4 and CD40 ligand (CD40L), human B cells can be expanded without difficulties from small amounts of peripheral blood within 14 days to very large amounts of highly-pure CD40-B cells (&gt;109 cells per patient) from healthy donors as well as cancer patients1-4. CD40-B cells express important lymph node homing molecules and can attract T cells in vitro5. Furthermore they efficiently take up, process and present antigens to T cells6,7. CD40-B cells were shown to not only prime na&iacute;ve, but also expand memory T cells8,9. Therefore CD40-activated B cells (CD40-B cells) have been studied as an alternative source of immuno-stimulatory antigen-presenting cells (APC) for cell-based immunotherapy1,5,10. In order to further study whether CD40-B cells induce effective T cell responses in vivo and to study the underlying mechanism we established a cell culture system for the generation of murine CD40-activated B cells. Using splenocytes or purified B cells from C57BL/6 mice for CD40-activation, optimal conditions were identified as follows: Starting from splenocytes of C57BL/6 mice (haplotype H-2b) lymphocytes are purified by density gradient centrifugation and co-cultured with HeLa cells expressing recombinant murine CD40 ligand (tmuCD40L HeLa)11. Cells are recultured every 3-4 days and key components such as CD40L, interleukin-4, -Mercaptoethanol and cyclosporin A are replenished. In this protocol we demonstrate how to obtain fully activated murine CD40-B cells (mCD40B) with similar APC-phenotype to human CD40-B cells (Fig 1a,b). CD40-stimulation leads to a rapid outgrowth and expansion of highly pure (&gt;90%) CD19+ B cells within 14 days of cell culture (Fig 1c,d). To avoid contamination with non-transfected cells, expression of the murine CD40 ligand on the transfectants has to be controlled regularly (Fig 2). Murine CD40-activated B cells can be used to study B-cell activation and differentiation as well as to investigate their potential to function as APC in vitro and in vivo. Moreover, they represent a promising tool for establishing therapeutic or preventive vaccination against tumors and will help to answer questions regarding safety and immunogenicity of this approach12.

In this video, we demonstrate the procedure of CD40-activation and expansion of murine B cells from splenocytes of C57BL/6 mice, which can be used as a model antigen-presenting cell (APC) to study induction of immunity.

Research on B cells has shown that CD40 activation improves their antigen presentation capacity. When stimulated with interleukin-4 and CD40 ligand ...

Recombinant Retroviral Production and Infection of B Cells

The transgenic expression of genes in eukaryotic cells is a powerful reverse genetic approach in which a gene of interest is expressed under the control of a heterologous expression system to facilitate the analysis of the resulting phenotype. This approach can be used to express a gene that is not normally found in the organism, to express a mutant form of a gene product, or to over-express a dominant-negative form of the gene product. It is particularly useful in the study of the hematopoetic system, where transcriptional regulation is a major control mechanism in the development and differentiation of B cells 1, reviewed in 2-4.
Mouse genetics is a powerful tool for the study of human genes and diseases. A comparative analysis of the mouse and human genome reveals conservation of synteny in over 90% of the genome 5. Also, much of the technology used in mouse models is applicable to the study of human genes, for example, gene disruptions and allelic replacement 6. However, the creation of a transgenic mouse requires a great deal of resources of both a financial and technical nature. Several projects have begun to compile libraries of knock out mouse strains (KOMP, EUCOMM, NorCOMM) or mutagenesis induced strains (RIKEN), which require large-scale efforts and collaboration 7. Therefore, it is desirable to first study the phenotype of a desired gene in a cell culture model of primary cells before progressing to a mouse model. 
Retroviral DNA integrates into the host DNA, preferably within or near transcription units or CpG islands, resulting in stable and heritable expression of the packaged gene of interest while avoiding transcriptional silencing 8 9. The genes are then transcribed under the control of a high efficiency retroviral promoter, resulting in a high efficiency of transcription and protein production. Therefore, retroviral expression can be used with cells that are difficult to transfect, provided the cells are in an active state during mitosis. Because the structural genes of the virus are contained within the packaging cell line, the expression vectors used to clone the gene of interest contain no structural genes of the virus, which both eliminates the possibility of viral revertants and increases the safety of working with viral supernatants as no infectious virions are produced 10. 
Here we present a protocol for recombinant retroviral production and subsequent infection of splenic B cells. After isolation, the cultured splenic cells are stimulated with Th derived lymphokines and anti-CD40, which induces a burst of B cell proliferation and differentiation 11. This protocol is ideal for the study of events occurring late in B cell development and differentiation, as B cells are isolated from the spleen following initial hematopoetic events but prior to antigenic stimulation to induce plasmacytic differentiation.

An efficient system of structure and function analysis of a gene in an ex vivo culture of splenic B-lymphocytes is described. This method takes advantage of recombinant retroviral production in a helper free, ecotrophic packaging cell line. Stable, heritable expression of a gene of interest within primary lymphocytes is achieved leading to generation of surface antibodies on B cells undergoing class switch recombination.

The transgenic expression of genes in eukaryotic cells is a powerful reverse genetic approach in which a gene of interest is expressed under the control ...

Identifying DNA Mutations in Purified Hematopoietic Stem/Progenitor Cells

In recent years, it has become apparent that genomic instability is tightly related to many developmental disorders, cancers, and aging. Given that stem cells are responsible for ensuring tissue homeostasis and repair throughout life, it is reasonable to hypothesize that the stem cell population is critical for preserving genomic integrity of tissues. Therefore, significant interest has arisen in assessing the impact of endogenous and environmental factors on genomic integrity in stem cells and their progeny, aiming to understand the etiology of stem-cell based diseases.
LacI transgenic mice carry a recoverable &#955;&#160;phage vector encoding the LacI reporter system, in which the LacI gene serves as the mutation reporter. The result of a mutated LacI gene is the production of &#946;-galactosidase that cleaves a chromogenic substrate, turning it blue. The LacI reporter system is carried in all cells, including stem/progenitor cells and can easily be recovered and used to subsequently infect E. coli. After incubating infected E. coli on agarose that contains the correct substrate, plaques can be scored; blue plaques indicate a mutant LacI gene, while clear plaques harbor wild-type. The frequency of blue (among clear) plaques indicates the mutant frequency in the original cell population the DNA was extracted from. Sequencing the mutant LacI gene will show the location of the mutations in the gene and the type of mutation.
The LacI transgenic mouse model is well-established as an in vivo mutagenesis assay. Moreover, the mice and the reagents for the assay are commercially available. Here we describe in detail how this model can be adapted to measure the frequency of spontaneously occurring DNA mutants in stem cell-enriched Lin-IL7R-Sca-1+cKit++(LSK) cells and other subpopulations of the hematopoietic system.

Here we describe an in vivo mutagenesis assay for small numbers of purified hematopoietic cells using the LacI transgenic mouse model.&#160;The LacI gene can be isolated to determine the frequency, location, and type of DNA mutants&#160;spontaneously arisen or after exposure to genotoxins.

In recent years, it has become apparent that genomic instability is tightly related to many developmental disorders, cancers, and aging. Given that stem ...

Detection of True IgE-expressing Mouse B Lineage Cells

B lymphocyte immunoglobulin heavy chain (IgH) class switch recombination (CSR) is a process wherein initially expressed IgM switches to other IgH isotypes, such as IgA, IgE and IgG. Measurement of IgH CSR in vitro is a key method for the study of a number of biologic processes ranging from DNA recombination and repair to aspects of molecular and cellular immunology. In vitro CSR assay involves the flow cytometric measurement surface Ig expression on activated B cells. While measurement of IgA and IgG subclasses is straightforward, measurement of IgE by this method is problematic due to soluble IgE binding to Fc&#949;RII/CD23 expressed on the surface of activated B cells. Here we describe a unique procedure for accurate measurement of IgE-producing mouse B cells that have undergone CSR in culture. The method is based on trypsin-mediated cleavage of IgE-CD23 complexes on cell surfaces, allowing for detection of IgE-producing B lineage cells by cytoplasmic staining. This procedure offers a convenient solution for flow cytometric analysis of CSR to IgE.

In vitro analysis of class switch recombination in mice is challenging due to cytophilic IgE molecules bound to Fc receptors on the surface of B cells. We describe a method for IgE detection using trypsin-mediated cleavage of surface-bound IgE prior to fixation and permeabilization for cytoplasmic fluorescence staining.

B lymphocyte immunoglobulin heavy chain (IgH) class switch recombination (CSR) is a process wherein initially expressed IgM switches to other IgH ...

Induction of Murine Intestinal Inflammation by Adoptive Transfer of Effector CD4+CD45RBhigh T Cells into Immunodeficient Mice

There are many different animal models available for studying the pathogenesis of human inflammatory bowel diseases (IBD), each with its own advantages and disadvantages. We describe here an experimental colitis model that is initiated by adoptive transfer of syngeneic splenic CD4+CD45RBhigh T cells into T and B cell deficient recipient mice. The CD4+CD45RBhigh T cell population that largely consists of na&#239;ve effector cells is capable of inducing chronic intestinal inflammation, closely resembling key aspects of human IBD. This method can be manipulated to study aspects of disease onset and progression. Additionally it can be used to study the function of innate, adaptive, and regulatory immune cell populations, and the role of environmental exposures, i.e., the microbiota, in intestinal inflammation. In this article we illustrate the methodology for inducing colitis with a step-by-step protocol. This includes a video demonstration of key technical aspects required to successfully develop this murine model of experimental colitis for research purposes.

Induction of Murine Intestinal Inflammation by Adoptive Transfer of Effector CD4+CD45RBhigh T Cells into Immunodeficient Mice

Here, we present a protocol to induce colonic inflammation in mice by adoptive transfer of syngeneic CD4+CD45RBhigh T cells into T and B cell deficient recipients. Clinical and histopathological features mimic human inflammatory bowel diseases. This method allows the study of the initiation of colonic inflammation and progression of disease.

There are many different animal models available for studying the pathogenesis of human inflammatory bowel diseases (IBD), each with its own advantages ...

Assessment of the Immunomodulatory Properties of Human Mesenchymal Stem Cells (MSCs)

The immunomodulatory properties of multilineage human mesenchymal stem cells (MSCs) appear to be highly relevant for clinical use towards a wide-range of immune-related diseases. Mechanisms involved are increasingly being elucidated and in this article, we describe the basic experiment to assess MSC immunomodulation by assaying for suppression of effector leukocyte proliferation. Representing activation, leukocyte proliferation can be assessed by a number of techniques, and we describe in this protocol the use of the fluorescent cellular dye carboxyfluorescein succinimidyl ester (CFSE) to label leukocytes with subsequent flow cytometric analyses. This technique can not only assess proliferation without radioactivity, but also the number of cell divisions that have occurred as well as allowing for identification of the specific population of proliferating cells and intracellular cytokine/factor expression. Moreover, the assay can be tailored to evaluate specific populations of effector leukocytes by magnetic bead surface marker selection of single peripheral blood mononuclear cell populations prior to co-culture with MSCs. The flexibility of this co-culture assay is useful for investigating cellular interactions between MSCs and leukocytes.

Assessment of the Immunomodulatory Properties of Human Mesenchymal Stem Cells MSCs

The immunomodulatory properties of human mesenchymal stem cells (MSC) appear increasingly relevant for clinical application. Using a co-culture system of MSCs and peripheral blood leukocytes pre-stained with the fluorescent dye carboxyfluorescein succinimidyl ester (CFSE), we describe the in vitro assessment of MSC immunomodulation on effector leukocyte proliferation and specific subpopulations.

The immunomodulatory properties of multilineage human mesenchymal stem cells (MSCs) appear to be highly relevant for clinical use towards a wide-range of ...

A Murine Model of Group B Streptococcus Vaginal Colonization

Streptococcus agalactiae (group B Streptococcus, GBS), is a Gram-positive, asymptomatic colonizer of the human gastrointestinal tract and vaginal tract of 10 - 30% of adults. In immune-compromised individuals, including neonates, pregnant women, and the elderly, GBS may switch to an invasive pathogen causing sepsis, arthritis, pneumonia, and meningitis. Because GBS is a leading bacterial pathogen of neonates, current prophylaxis is comprised of late gestation screening for GBS vaginal colonization and subsequent peripartum antibiotic treatment of GBS-positive mothers. Heavy GBS vaginal burden is a risk factor for both neonatal disease and colonization. Unfortunately, little is known about the host and bacterial factors that promote or permit GBS vaginal colonization. This protocol describes a technique for establishing persistent GBS vaginal colonization using a single &#946;-estradiol pre-treatment and daily sampling to determine bacterial load. It further details methods to administer additional therapies or reagents of interest and to collect vaginal lavage fluid and reproductive tract tissues. This mouse model will further the understanding of the GBS-host interaction within the vaginal environment, which will lead to potential therapeutic targets to control maternal vaginal colonization during pregnancy and to prevent transmission to the vulnerable newborn. It will also be of interest to increase our understanding of general bacterial-host interactions in the female vaginal tract.

A Murine Model of Group B Streptococcus Vaginal Colonization

The purpose of this protocol is to imitate human group B Streptococcus (GBS) vaginal colonization in a murine model. This method may be used to investigate host immune responses and bacterial factors contributing to GBS vaginal persistence, as well as to test therapeutic strategies.

Streptococcus agalactiae (group B Streptococcus, GBS), is a Gram-positive, asymptomatic colonizer of the human gastrointestinal tract and vaginal tract of ...

Flow Cytometric Analysis of Particle-bound Bet v 1 Allergen in PM10

Flow cytometry is a method widely used to quantify suspended solids such as cells or bacteria in a size range from 0.5 to several tens of micrometers in diameter. In addition to a characterization of forward and sideward scatter properties, it enables the use of fluorescent labeled markers like antibodies to detect respective structures. Using indirect antibody staining, flow cytometry is employed here to quantify birch pollen allergen (precisely Bet v 1)-loaded particles of 0.5 to 10 &#181;m in diameter in inhalable particulate matter (PM10, particle size &#8804;10 &#181;m in diameter). PM10 particles may act as carriers of adsorbed allergens possibly transporting them to the lower respiratory tract, where they could trigger allergic reactions.
So far the allergen content of PM10 has been studied by means of enzyme linked immunosorbent assays (ELISAs) and scanning electron microscopy. ELISA measures the dissolved and not the particle-bound allergen. Compared to scanning electron microscopy, which can visualize allergen-loaded particles, flow cytometry may additionally quantify them. As allergen content of ambient air can deviate from birch pollen count, allergic symptoms might perhaps correlate better with allergen exposure than with pollen count. In conjunction with clinical data, the presented method offers the opportunity to test in future experiments whether allergic reactions to birch pollen antigens are associated with the Bet v 1 allergen content of PM10 particles &#62;0.5 &#181;m.

Here, we present a protocol to quantify allergen-loaded particles by flow cytometry. Ambient particulate matter particles may act as carriers of adsorbed allergens. We show here that flow cytometry, a method widely used to characterize suspended solids &#62;0.5 &#181;m in diameter, can be used to measure these allergen-loaded particles.

Flow cytometry is a method widely used to quantify suspended solids such as cells or bacteria in a size range from 0.5 to several tens of micrometers in ...

Genome-wide Analysis of HDAC Inhibitor-mediated Modulation of microRNAs and mRNAs in B Cells Induced to Undergo Class-switch DNA Recombination and Plasma Cell Differentiation

Antibody responses are accomplished through several critical B cell-intrinsic processes, including somatic hypermutation (SHM), class-switch DNA recombination (CSR), and plasma cell differentiation. In recent years, epigenetic modifications or factors, such as histone deacetylation and microRNAs (miRNAs), have been shown to interact with B-cell genetic programs to shape antibody responses, while the dysfunction of epigenetic factors has been found to lead to autoantibody responses. Analyzing genome-wide miRNA and mRNA expression in B cells in response to epigenetic modulators is important for understanding the epigenetic regulation of B-cell function and antibody response. Here, we demonstrate a protocol for inducing B cells to undergo CSR and plasma cell differentiation, treating these B cells with histone deacetylase (HDAC) inhibitors (HDIs), and analyzing mRNA and microRNA expression. In this protocol, we directly analyze complementary DNA (cDNA) sequences using next-generation mRNA sequencing (mRNA-seq) and miRNA-seq technologies, mapping of the sequencing reads to the genome, and quantitative reverse transcription (qRT)-PCR. With these approaches, we have defined that, in B cells induced to undergo CSR and plasma cell differentiation, HDI, an epigenetic regulator, selectively modulates miRNA and mRNA expression and alters CSR and plasma cell differentiation.

Epigenetic factors can interact with genetic programs to modulate gene expression and regulate B cell function. By combining in vitro B-cell stimulation, qRT-PCR, and high-throughput microRNA-sequence and mRNA-sequence approaches, we can analyze the epigenetic modulation of miRNA and gene expression in B cells.

Antibody responses are accomplished through several critical B cell-intrinsic processes, including somatic hypermutation (SHM), class-switch DNA ...

In Vitro and In Vivo Assessment of T, B and Myeloid Cells Suppressive Activity and Humoral Responses from Transplant Recipients

The main concern in transplantation is to achieve specific tolerance through induction of regulatory cells. The understanding of tolerance mechanisms requires reliable models. Here, we describe models of tolerance to cardiac allograft in rat, induced by blockade of costimulation signals or by upregulation of immunoregulatory molecules through gene transfer. Each of these models allowed in vivo generation of regulatory cells such as regulatory T cells (Tregs), regulatory B cells (Bregs) or regulatory myeloid cells (RegMCs). In this manuscript, we describe two complementary protocols that have been used to identify and define in vitro and in vivo regulatory cell activity to determine their responsibility in tolerance induction and maintenance. First, an in vitro suppressive assay allowed rapid identification of cells with suppressive capacity on effector immune responses in a dose dependent manner, and can be used for further analysis such as cytokine measurement or cytotoxicity. Second, the adoptive transfer of cells from a tolerant treated recipient to a newly irradiated grafted recipient, highlighted the tolerogenic properties of these cells in controlling graft directed immune responses and/or converting new regulatory cells (termed infectious tolerance). These methods are not restricted to cells with known phenotypic markers and can be extended to any cell population. Furthermore, donor directed allospecificity of regulatory cells (an important goal in the field) can be assessed by using third party donor cells or graft either in vitro or in vivo. Finally, to determine the specific tolerogenic capacity of these regulatory cells, we provide protocols to assess the humoral anti-donor antibody responses and the capacity of the recipient to develop humoral responses against new or former known antigens. The models of tolerance described can be used to further characterize regulatory cells, to identify new biomarkers, and immunoregulatory molecules, and are adaptable to other transplantation models or autoimmune diseases in rodent or human.

In Vitro and In Vivo Assessment of T, B and Myeloid Cells Suppressive Activity and Humoral Responses from Transplant Recipients

Here, we present a protocol to induce tolerance in transplantation, and assess in vitro and in vivo the suppressive capacity of distinct cell subsets from the recipient and the immune status of the recipient toward donor or exogenous antigens.

The main concern in transplantation is to achieve specific tolerance through induction of regulatory cells. The understanding of tolerance mechanisms ...