Nitya Jain was supported by an NIH/NIAID Career Transition Award 1K22AI116661-01.

All animal procedures were performed with the approval of and in compliance with the Institutional Animal Care and Use Committee (IACUC) at Massachusetts General Hospital.
CAUTION: This protocol involves the use of a class 3b laser (LG3). LG3 laser safety goggles must always be used when operating this laser. Appropriate training and safety guidelines must be followed to avoid the risk of injury.
1. Design and Assembly of Laser
<ol>
	<li>Connect the light-emitting...

<ol>
	<li>Maynard, C. L., Elson, C. O., Hatton, R. D., Weaver, C. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reciprocal+interactions+of+the+intestinal+microbiota+and+immune+system.">Reciprocal interactions of the intestinal microbiota and immune system.</a> Nature. 489, 231-241 (2012).</li><li>Paun, A., Yau, C., Danska, J. 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+Influence+of+the+Microbiome+on+Type+1+Diabetes.">The Influence of the Microbiome on Type 1 Diabetes.</a> Journal of Immunology. 198, 590-595 (2017).</li><li>Mathis, D., Benoist, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microbiota+and+autoimmune+disease:+the+hosted+self.">Microbiota and autoimmune disease: the hosted self.</a> Cell Host Microbe. 10, 297-301 (2011).</li><li>Kollmann, T. R., Kampmann, B., Mazmanian, S. K., Marchant, A., Levy, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Protecting+the+Newborn+and+Young+Infant+from+Infectious+Diseases:+Lessons+from+Immune+Ontogeny.">Protecting the Newborn and Young Infant from Infectious Diseases: Lessons from Immune Ontogeny.</a> Immunity. 46, 350-363 (2017).</li><li>Jain, N., Walker, W. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diet+and+host-microbial+crosstalk+in+postnatal+intestinal+immune+homeostasis.">Diet and host-microbial crosstalk in postnatal intestinal immune homeostasis.</a> Nature Reviews in Gastroenterology and Hepatology. 12, 14-25 (2015).</li><li>Mowat, A. M., Agace, W. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regional+specialization+within+the+intestinal+immune+system.">Regional specialization within the intestinal immune system.</a> Nature Reviews in Immunology. 14, 667-685 (2014).</li><li>Macpherson, A. J., Uhr, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Induction+of+protective+IgA+by+intestinal+dendritic+cells+carrying+commensal+bacteria.">Induction of protective IgA by intestinal dendritic cells carrying commensal bacteria.</a> Science. 303, 1662-1665 (2004).</li><li>Mowat, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anatomical+basis+of+tolerance+and+immunity+to+intestinal+antigens.">Anatomical basis of tolerance and immunity to intestinal antigens.</a> Nature Reviews in Immunology. 3, 331-341 (2003).</li><li>Diehl, G. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microbiota+restricts+trafficking+of+bacteria+to+mesenteric+lymph+nodes+by+CX(3)CR1(hi)+cells.">Microbiota restricts trafficking of bacteria to mesenteric lymph nodes by CX(3)CR1(hi) cells.</a> Nature. 494 (3), 116-120 (2013).</li><li>Pham, A. H., McCaffery, J. M., Chan, D. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mouse+lines+with+photo-activatable+mitochondria+to+study+mitochondrial+dynamics.">Mouse lines with photo-activatable mitochondria to study mitochondrial dynamics.</a> Genesis. 50, 833-843 (2012).</li><li>Conway, K. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ATG5+regulates+plasma+cell+differentiation.">ATG5 regulates plasma cell differentiation.</a> Autophagy. 9, 528-537 (2013).</li><li>Buzoni-Gatel, D., Lepage, A. C., Dimier-Poisson, I. H., Bout, D. T., Kasper, L. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adoptive+transfer+of+gut+intraepithelial+lymphocytes+protects+against+murine+infection+with+Toxoplasma+gondii.">Adoptive transfer of gut intraepithelial lymphocytes protects against murine infection with Toxoplasma gondii.</a> Journal of Immunology. 158, 5883-5889 (1997).</li><li>Guo, X., Muite, K., Wroblewska, J., Fu, Y. X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Purification+and+Adoptive+Transfer+of+Group+3+Gut+Innate+Lymphoid+Cells.">Purification and Adoptive Transfer of Group 3 Gut Innate Lymphoid Cells.</a> Methods in Molecular Biology. 1422, 189-196 (2016).</li><li>Morton, A. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endoscopic+photoconversion+reveals+unexpectedly+broad+leukocyte+trafficking+to+and+from+the+gut.">Endoscopic photoconversion reveals unexpectedly broad leukocyte trafficking to and from the gut.</a> Proceedings of the National Academy of Sciences of the United States of America. 111, 6696-6701 (2014).</li></ol>

The identification and characterization of cells that interact with and are influenced by the microbiota in the colon are important and should facilitate understanding of how information from the mucosal microenvironment is relayed to the rest of the body. One method for studying gut-related cell migration requires the isolation of gut-associated cells followed by an adoptive transfer into recipient mice to determine their tissue-homing patterns and function12,13...

The mammalian gastrointestinal tract harbors hundreds of species of bacteria that exist in a symbiotic relationship with the host1. The immune cells present in the local milieu enforce a peaceful coexistence with these microbes and establish a protective barrier against pathogen invasions. Thus, bi-directional interactions between the immune cells and the microbiota are critical to establish a commensal community that educates the host immune system and sets the threshold for immune reactivity to pathogens. Changes in the microbial composition, or dysbiosis, can disturb the immune homeostasis and perturb regulatory circuits that restrain intestinal inflammations leading to immune-mediated diseases such as Type 1 Diabetes and IBD2,3.
The period immediately after birth is a unique developmental window during which the intestinal microbial communities begin to establish at the same time the immune system matures4. The postnatal microbiota is not stable, with shifts in the community composition occurring naturally and frequently5. The immune cells that interact with the microbiota reside in two distinct anatomical locations in the intestine - the lamina propria and the intestinal epithelium6. Numerous types of immune cells are present in the intestine, including lymphocytes (such as T cells, B cells, and innate lymphoid cells) as well as myeloid cells (which include dendritic cells, monocytes, and macrophages). These cells, also known as hematopoietic cells, perform a multitude of functions that preserve the intestinal barrier and maintain homeostasis.
In addition to their regulatory functions at intestinal sites, immune cells of the mucosa may also carry microbial messages to the extra-intestinal sites to regulate systemic immunity7,8,9. This is an area of growing research interest and highlights the need for methods to identify immune cells that migrate out of intestinal tissues in order to probe their function. The protocol reported here utilizes a commercially available mouse model in which a photoconvertible fluorescent protein is exploited to label cells. PhAMexcised mice ubiquitously express a green fluorescent Dendra2 protein that is irreversibly switched to red fluorescence upon activation by ultraviolet (UV) light10. Using a fiber optic cannula to deliver 405 nm light into the colon of newborn mice, we demonstrate that photoconverted hematopoietic cells, which have originated in or transited through the colon can be found in the spleen.

<table border="0" cellpadding="0" cellspacing="0" style="width:873px;" width="874">
	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:873px;">Laser</td>
			<td style="width:201px;"></td>
			<td style="width:167px;"></td>
			<td style="width:247px;"></td>
		</tr>
		<tr height="168">
			<td height="168" style="height:168px;width:259px;">Light Emitting Diode (LED)</td>
			<td style="width:201px;">THORLABS</td>
			<td style="width:167px;">M405FP1</td>
			<td style="width:247px;">CAUTION: this is a Class 3b laser. Safety goggles must be worn when using the laser. It emits a 405 nm wavelength with a current of 1400 mA. It is fiber-coupled. It accepts SMA connector. https://www.thorlabs.com/thorproduct.cfm?partnumber=M405FP1</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:259px;">LED driver</td>
			<td style="width:201px;">THORLABS</td>
			<td style="width:167px;">LEDD1B</td>
			<td style="width:247px;">Drives a constant current of 1200 mA through the laser. https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=2616</td>
		</tr>
		<tr height="105">
			<td height="105" style="height:105px;width:259px;">Optogenetics patch cable</td>
			<td style="width:201px;">THORLABS</td>
			<td style="width:167px;">M87L01</td>
			<td style="width:247px;">1 m long cable with an SMA connector. https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=11405&#38;pn=M87L01#11454</td>
		</tr>
		<tr height="147">
			<td height="147" style="height:147px;width:259px;">Fiber optic cannula</td>
			<td style="width:201px;">Doric lenses&#160;</td>
			<td style="width:167px;">MFC_480/500-0.5_5mm_ZF1.25_C45</td>
			<td style="width:247px;">5 mm long cannula with an outer diameter of 500 &#181;m and an inner diameter of 480 &#181;m. The NA value is 0.5. The ferrule is zirconia, 1.25 mm OD. https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=6036</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:259px;">Power supply</td>
			<td style="width:201px;">THORLABS</td>
			<td style="width:167px;">KPS101</td>
			<td style="width:247px;">Supplies 15 V with a current of 2.4 A https://www.thorlabs.com/search/thorsearch.cfm?search=KPS101</td>
		</tr>
		<tr height="105">
			<td height="105" style="height:105px;width:259px;">LG3 laser safety goggles&#160;</td>
			<td style="width:201px;">THORLABS</td>
			<td style="width:167px;">LG3</td>
			<td style="width:247px;">Orange lenses with 47% visible light transmission https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=762&#38;pn=LG3#2523</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;">Red light&#160;</td>
			<td>Electron Microscopy Sciences</td>
			<td>74327-10</td>
			<td style="width:247px;">15 W lamp https://us.vwr.com/store/product/12360027/paterson-safelight-electron-microscopy-sciences</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:873px;">Intestinal cell isolation</td>
			<td style="width:201px;"></td>
			<td style="width:167px;"></td>
			<td style="width:247px;"></td>
		</tr>
		<tr height="168">
			<td height="168" style="height:168px;width:259px;">Isoflurane</td>
			<td style="width:201px;">Patterson Veterinary</td>
			<td style="width:167px;">07-893-1389</td>
			<td style="width:247px;">CAUTION: inhalation of this anesthetic may cause dizziness, drowsiness, or even unconsciousness. This anesthetic should be used in a Class II hood.&#160; https://www.pattersonvet.com/Supplies/ProductFamilyDetails/PIF_762328?carouselPageNumber=3</td>
		</tr>
		<tr height="147">
			<td height="147" style="height:147px;width:259px;">1X HBSS</td>
			<td style="width:201px;">Gibco</td>
			<td style="width:167px;">14025076</td>
			<td style="width:247px;">Ca/Mg free https://www.fishersci.com/shop/products/gibco-hbss-calcium-magnesium-no-phenol-red-4/14025076?searchHijack=true&#38;searchTerm=14025076&#38;searchType=RAPID&#38;matchedCatNo=14025076</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:259px;">Calf Serum</td>
			<td style="width:201px;">Hyclone AZM</td>
			<td style="width:167px;">197696</td>
			<td></td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:259px;">EDTA</td>
			<td style="width:201px;">Invitrogen</td>
			<td style="width:167px;">15575020</td>
			<td style="width:247px;">0.5 M concentration https://www.thermofisher.com/order/catalog/product/15575020?SID=srch-srp-15575020</td>
		</tr>
		<tr height="126">
			<td height="126" style="height:126px;width:259px;">DTT</td>
			<td style="width:201px;">Sigma</td>
			<td style="width:167px;">10197777001</td>
			<td style="width:247px;">CAUTION: harmful if swallowed and causes skin irritation. 1 M concentration https://www.sigmaaldrich.com/catalog/product/roche/dttro?lang=en&#38;region=US</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:259px;">HEPES</td>
			<td style="width:201px;">Gibco</td>
			<td style="width:167px;">15630080</td>
			<td style="width:247px;">1 M concentration https://www.thermofisher.com/order/catalog/product/15630080?SID=srch-hj-15630080</td>
		</tr>
		<tr height="126">
			<td height="126" style="height:126px;width:259px;">Petri dish</td>
			<td style="width:201px;">Corning</td>
			<td style="width:167px;">353004</td>
			<td style="width:247px;">https://www.fishersci.com/shop/products/falcon-easy-grip-tissue-culture-dishes-2/08772f?searchHijack=true&#38;searchTerm=08772F&#38;searchType=RAPID&#38;matchedCatNo=08772F</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:259px;">70 micron cell strainer</td>
			<td style="width:201px;">Falcon</td>
			<td style="width:167px;">352350</td>
			<td style="width:247px;">https://www.fishersci.com/shop/products/falcon-cell-strainers-4/087712</td>
		</tr>
		<tr height="168">
			<td height="168" style="height:168px;width:259px;">Micro magnetic stir bar</td>
			<td style="width:201px;">Fisherbrand</td>
			<td style="width:167px;">1451364</td>
			<td style="width:247px;">Rinse in 70% ethanol after each use. Rinse several times in distilled water prior to each use. The bar is 8 mm long with an octagonal shape. https://www.fishersci.com/shop/products/fisherbrand-octagonal-magnetic-stir-bars-12/1451364#?keyword=1451364</td>
		</tr>
		<tr height="168">
			<td height="168" style="height:168px;width:259px;">Magnetic stir plate</td>
			<td style="width:201px;">Corning Laboratory Stirrers</td>
			<td style="width:167px;">440826</td>
			<td style="width:247px;">https://www.coleparmer.com/i/corning-440826-nine-position-stirrer-120-vac-60-hz/8430420?PubID=UX&#38;persist=true&#38;ip=no&#38;gclid=CjwKCAiAqbvTBRAPEiwANEkyCLPLrWABXmOUI0QE53NLV0Owxlcs2V1K6rWbRPOwlcVVDq000FBiQxoCqQAQAvD_BwE</td>
		</tr>
		<tr height="147">
			<td height="147" style="height:147px;width:259px;">Collagenase</td>
			<td style="width:201px;">Roche</td>
			<td style="width:167px;">5401020001</td>
			<td style="width:247px;">https://www.sigmaaldrich.com/catalog/product/roche/05401020001?lang=en&#38;region=US&#38;gclid=CjwKCAiAjuPRBRBxEiwAeQ2QPhE44qlvxjmo1PYu3zCas3w-_d6P9gKjXW82-c1EOm6NjPHCc5WuixoC_0IQAvD_BwE</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:259px;">DNase I</td>
			<td style="width:201px;">Sigma</td>
			<td style="width:167px;">10104159001</td>
			<td style="width:247px;">https://www.sigmaaldrich.com/catalog/product/roche/10104159001?lang=en&#38;region=US</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:259px;">1X PBS</td>
			<td style="width:201px;">Gibco</td>
			<td style="width:167px;">20012-027</td>
			<td style="width:247px;">https://www.thermofisher.com/order/catalog/product/20012027?SID=srch-hj-20012-027</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:259px;">Pipet aid</td>
			<td style="width:201px;">Thermo Scientific</td>
			<td style="width:167px;">14387165</td>
			<td style="width:247px;">https://www.fishersci.com/shop/products/s1-pipette-fillers/14387165#?keyword=14387165</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:259px;">10 mL serological pipet</td>
			<td style="width:201px;">Falcon</td>
			<td style="width:167px;">357530</td>
			<td style="width:247px;">https://www.fishersci.com/shop/products/falcon-serological-pipets-bulk-pack-5/p-163659</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:259px;">25 mL serological pipet</td>
			<td style="width:201px;">Falcon</td>
			<td style="width:167px;">357515</td>
			<td style="width:247px;">https://www.fishersci.com/shop/products/falcon-serological-pipets-bulk-pack-5/p-163659</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:259px;">15 mL conical centrifuge tube</td>
			<td style="width:201px;">Thermo Scientific</td>
			<td style="width:167px;">339651</td>
			<td style="width:247px;">https://www.thermofisher.com/order/catalog/product/339650</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:259px;">50 mL conical centrifuge tube</td>
			<td style="width:201px;">Thermo Scientific</td>
			<td style="width:167px;">339653</td>
			<td style="width:247px;">https://www.thermofisher.com/order/catalog/product/339650</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:873px;">Single cell suspension</td>
			<td style="width:201px;"></td>
			<td style="width:167px;"></td>
			<td style="width:247px;"></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:259px;">Eppendorf tubes</td>
			<td style="width:201px;">Seal-Rite</td>
			<td style="width:167px;">1615-5500</td>
			<td style="width:247px;">Holds 1.5 mL. https://www.usascientific.com/Seal-Rite-1.5-ml-tube.aspx</td>
		</tr>
		<tr height="105">
			<td height="105" style="height:105px;width:259px;">Tissue homogenizer&#160;</td>
			<td style="width:201px;">Kimble</td>
			<td>K7495400000</td>
			<td style="width:247px;">Requires 2 AA batteries. https://www.fishersci.com/shop/products/kontes-pellet-pestle-cordless-motor-cordless-motor/k7495400000</td>
		</tr>
		<tr height="126">
			<td height="126" style="height:126px;width:259px;">Homogenizer tips&#160;</td>
			<td style="width:201px;">Kimble</td>
			<td style="width:167px;">7495210590</td>
			<td style="width:247px;">Plastic, 0.5 mL tips https://www.fishersci.com/shop/products/kimble-chase-kontes-pellet-pestle-14/k7495210590#?keyword=7495210590</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:259px;">ACK lysing buffer</td>
			<td style="width:201px;">Gibco</td>
			<td style="width:167px;">A10492-01</td>
			<td style="width:247px;">https://www.thermofisher.com/order/catalog/product/A1049201?SID=srch-hj-A10492-01</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:259px;">40 micron cell strainer</td>
			<td style="width:201px;">Falcon</td>
			<td style="width:167px;">08-771-1</td>
			<td style="width:247px;">https://www.fishersci.com/shop/products/falcon-cell-strainers-4/087711</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:873px;">Antibodies</td>
			<td style="width:201px;"></td>
			<td style="width:167px;"></td>
			<td style="width:247px;"></td>
		</tr>
		<tr height="147">
			<td height="147" style="height:147px;width:259px;">BV786 anti-mouse CD45&#160;</td>
			<td style="width:201px;">BD</td>
			<td style="width:167px;">564225</td>
			<td style="width:247px;">Clone 3O-F11 https://www.bdbiosciences.com/us/reagents/research/antibodies-buffers/immunology-reagents/anti-mouse-antibodies/cell-surface-antigens/bv786-rat-anti-mouse-cd45-30-f11/p/564225</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">Live/Dead</td>
			<td>Invitrogen</td>
			<td>L34962</td>
			<td style="width:247px;">https://www.thermofisher.com/order/catalog/product/L34962</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:259px;">Other</td>
			<td style="width:201px;"></td>
			<td style="width:167px;"></td>
			<td style="width:247px;"></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;">Razor blades</td>
			<td>VWR</td>
			<td>55411-050</td>
			<td style="width:247px;">Use for decapitation. https://us.vwr.com/store/product/4548306/vwr-razor-blades</td>
		</tr>
	</tbody>
</table>

in vivo photolabeling of cells in the colon to assess migratory potential of hematopoietic cells in neonatal mice

Enteric bacterial communities are established early in life and influence immune cell development and function. The neonatal microbiota is susceptible to numerous external influences including antibiotics use and diet, which impacts susceptibility to autoimmune and inflammatory diseases. Disorders such as Inflammatory Bowel Disease (IBD) are characterized by a massive influx of immune cells to the intestines. However, immune cells conditioned by the microbiota may additionally emigrate out of the intestines to influence immune responses at extra-intestinal sites. Thus, there is a need to identify and characterize cells that may carry microbial messages from the intestines to distal sites. Here, we describe a method to label cells in the colon of newborn mice in vivo that enables their identification at extra-intestinal sites after migration.

A fiber-optic cable was used to deliver 405 nm light into the colons of 2-day old PhAMexcised mice. In previous experiments, a 30 s exposure was determined to give a maximal photoconversion of colon cells with minimal cytotoxicity (Figure 1A). Therefore, sequential 30 s exposures of different segments of the colon were carried out as described in the protocol. Following the laser exposure, the mice were immediately euthanized, and ...

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In Vivo Photolabeling of Cells in the Colon to Assess Migratory Potential of Hematopoietic Cells in Neonatal Mice

The protocol described here utilizes a photolabeling approach in newborn mice to specifically identify immune cells that emigrate from the colon to extra-intestinal sites. This strategy will be useful to study host-microbiome interactions in early life.

In Vivo Photolabeling of Cells in the Colon to Assess Migratory Potential of Hematopoietic Cells in Neonatal Mice

Enteric bacterial communities are established early in life and influence immune cell development and function. The neonatal microbiota is susceptible to ...

This method can help answer key questions in the mucosal immunology field regarding neonatal host immune microbiome interactions such as do cells carry microbial messages, and if so which cells are they? The main advantage of this technique is that it non-specifically an irreversibly labels colon resident cells in infant mice, enabling us to determine their trafficking patterns to extra-intestinal sites. To assemble the laser, connect the light-emitting diode, or LED to the LED driver via the four-pin M8 connector cable of the LED and carefully tighten the screw to fasten the connection.Hold the connector opening of the LED up to the light to ensure that there are no visible obstructions. Insert the optogenetics patch cable into the opening. Insert the cannula into either end of the connector sleeve.Then attach the other end of the connector sleeve to the end of the patch cable, connecting the fiberoptic cannula to the fiberoptic patch cable. Use the continuous adjustment knob to set the LED driver to the continuous wave mode at zero, and the current limit set to 1.2 amps. When the laser is ready, plug the LED driver into a power source in a dark location.Use one hand to gently scruff the back of an anesthetized day 10 to 12 postnatal mouse with the index finger and thumb. Turn over the animal to expose the abdomen, and secure the tail between the ring and little fingers. Use the other hand to remove the protective cap from the cannula, and gently insert the fiberoptic cannula through the anus, into the colon, so that all five millimeters of the optical fiber are inside the mouse, maintaining the long axis of the cannula parallel to the mouse's midline.The design of the cannula including its flexibility, diameter, and length is critical to the success of this procedure. The neonatal pup is very fragile and great care must be taken to avoid perforating the colon. Wearing safety goggles, increase the laser current to the maximum value and confirm the presence of UV light by looking at the translucent abdomen of the animal.Withdraw the cannula approximately one millimeter every 30 seconds to maximize the luminal area exposed to the light. After two minutes total of UV light exposure, slowly remove the cannula from the mouse and turn off the laser. After recovering from anesthesia, return the mouse to the home cage.To harvest the intestinal lymphocytes, use clean forceps and scissors to open the abdomen, and reflect the intestines to one side to expose the colon. To remove the whole colon, first transect the tissue just distal to the cecum, and firmly grasping the colon with forceps, use scissors to cut through the urethra to the rectum. Then cut the colon as close to the anus as possible, and remove the entire colon from the abdominal cavity.Use forceps to push the contents out of the colon onto a dry paper towel. And transfer the clean colon onto the lid of a tissue culture dish. Use razor blades to finely chop the sample, and transfer the resulting paste into a cell strainer set in a Petri dish containing 10 milliliters of cold Hank's Balanced Buffer Solution supplemented with calf serum, or HBSS-CS.Add a clean eight millimeter long magnetic stir bar to the strainer and place the dish on a nine-position magnetic stirrer plate with a magnetic stir bar speed set to 800 RPM. After a five-minute incubation at room temperature, discard the buffer, and repeat the wash with 10 milliliters of HBSS-CS. Dissociate the epithelial cells with 10 milliliters of pre-warmed epithelial strip buffer and stir the cells at 800 RPM for 30 minutes in a 37-degree Celsius incubator.At the end of the incubation, transfer the enriched intestinal epithelial fraction into a 15 milliliter tube for centrifugation. And re-suspend the pellet in one milliliter of FACS buffer on ice. Next, wash the remaining lamina propria tissue in the strainer two times with HBSS-CS as just demonstrated, followed by two incubations in 10 milliliters of wash buffer supplemented with EDTA for 15 minutes at 37 degrees Celsius with stirring.Then wash the sample two more times with HBSS-CS, followed by a third incubation in 10 milliliters of EDTA-free wash buffer for 10 minutes at room temperature without stirring. At the end of the incubation wash the sample two more times with HBSS-CS, and digest the remaining lamina propria tissue in the cell strainer with 10 more milliliters of EDTA-wash buffer supplemented with Dnase I and collagenase with stirring at 800 RPM for 45 minutes at 37 degrees Celsius. At the end of the digestion filter the enzyme solution through a new strainer into a 50 milliliter conical tube and neutralize the collagenase activity with 20 milliliters of cold wash medium.Collect the lamina propria cells by centrifugation. And re-suspend the lamina propria lymphocyte pellet in one milliliter of FACS buffer. Then combine the intestinal epithelial lymphocytes and the lamina propria lymphocyte fractions, and stain the cells with the appropriate fluorescents conjugated antibodies of interest for flow cytometric analysis.A 30-second laser light exposure delivers a maximal photo conversion of colon cells with a minimal cytotoxicity. No fluorescents activated cells are detected in the colons of unlasered mice, while 405 nanometers of light exposure results in distinct dendra-r positive cell populations in both the CD45 negative and CD45 positive cell compartments. Of note, no background labeling is observed in the spleen, suggesting that the intracolonic laser beam does not penetrate enough to photolabel cells in extraintestinal sites.In this representative experiment, the migration of photoconverted intestinal cell migration from the colon to the spleen was evaluated with only CD4 positive cells identified three to five days after laser light exposure, consistent with the theory that CD45 negative cells within the colon are primarily epithelial and structural cells. Once mastered, the light exposure steps can be performed in approximately five minutes per mouse, while the entire sample collection and analysis takes about nine hours to be completed. After watching this video you should have a good understanding of how to label cells in the colons of newborn mice and to use flow cytometry to identify the labeled cells in the spleen after their migration.Don't forget that working with ultraviolet light and animal anesthetics can be extremely hazardous. Precautions such as wearing safety goggles and using an appropriate scavenging system should always be taken while working with these materials.

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5.7K visualizações.  Massachusetts General Hospital. This method can help answer key questions in the mucosal immunology field regarding neonatal host immune microbiome interactions such as do cells carry microbial messages, and if so which cells are they? The main advantage of this technique is that it non-specifically an irreversibly labels colon resident cells in infant mice, enabling us to determine their trafficking patterns to extra-intestinal sites. To assemble the laser, connect the light-emitting diode, or LED to the LED driver via the...