The authors would like to thank Mr. Ryan Hart and Mr. Arriz Lucas for their invaluable feedback on this communication. This work was supported by NIH NINDS R01 NS065052 and Phoenix Children&#8217;s Hospital Mission Support Funds.

NOTE: All procedures were carried out in compliance with The Institutional Animal Care and Use Committee (IACUC) of the University of Arizona. A list of recommended materials and equipment can be found in Table 1.
1. Tissue Preparation
<ol>
	<li>Perfusion
	<ol>
		<li>Euthanize rodent with an overdose of sodium pentobarbital (25 mg/kg, IP), and perfuse transcardially with phosphate buffered saline (PBS) until completely exsanguinated (3-5 min) at a flow rate of 8 ml/min. For ...

<ol>
	<li>Marrack, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemistry+of+antigens+and+antibodies.">Chemistry of antigens and antibodies.</a> Nature. 134, 468-469 (1934).</li><li>Coons, A. H., Creech, H. J., Jones, R. N., Berliner, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+demonstration+of+pneumococcal+antigen+in+tissues+by+the+use+of+fluorescent+antibody.">The demonstration of pneumococcal antigen in tissues by the use of fluorescent antibody.</a> J Immunol. 45, 159-170 (1942).</li><li>Marshall, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Localization+of+adrenocorticotropic+hormone+by+histochemical+and+immunochemical+methods.">Localization of adrenocorticotropic hormone by histochemical and immunochemical methods.</a> The Journal of experimental medicine. 94, 21-30 (1951).</li><li>Mellors, R. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Histochemical+demonstration+of+the+in+vivo+localization+of+antibodies:+antigenic+components+of+the+kidney+and+the+pathogenesis+of+glomerulonephritis.">Histochemical demonstration of the in vivo localization of antibodies: antigenic components of the kidney and the pathogenesis of glomerulonephritis.</a> The journal of histochemistry and cytochemistry : official journal of the Histochemistry Society. 3, 284-289 (1955).</li><li>Nakane, P. K., Pierce, G. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enzyme-labeled+antibodies:+preparation+and+application+for+the+localization+of+antigens.">Enzyme-labeled antibodies: preparation and application for the localization of antigens.</a> The journal of histochemistry and cytochemistry : official journal of the Histochemistry Society. 14, 929-931 (1966).</li><li>Avrameas, S., Uriel, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Method+of+antigen+and+antibody+labelling+with+enzymes+and+its+immunodiffusion+application.">Method of antigen and antibody labelling with enzymes and its immunodiffusion application.</a> Comptes rendus hebdomadaires des seances de l'Academie des sciences. Serie D: Sciences naturelles. 262, 2543-2545 (1966).</li><li>Cuello, A. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Immunohistochemistry. , (1983).</li><li>Junqueira, L. C. U., Mescher, A. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Junqueira's basic histology : text and atlas. , (2013).</li><li>Gage, G. J., Kipke, D. R., Shain, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Whole+animal+perfusion+fixation+for+rodents.">Whole animal perfusion fixation for rodents.</a> Journal of visualized experiments : JoVE. , (2012).</li><li>Christensen, N. K., Winther, L., Kumar, G. L., Rudbeck, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Education Guide: Immunohistochemical (IHC) staining methods. , 103-108 (2009).</li><li>Wang, G., Achim, C. L., Hamilton, R. L., Wiley, C. A., Soontornniyomkij, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tyramide+signal+amplification+method+in+multiple-label+immunofluorescence+confocal+microscopy).">Tyramide signal amplification method in multiple-label immunofluorescence confocal microscopy).</a> Methods. 18, 459-464 (1999).</li><li>Feldengut, S., Del Tredici, K., Braak, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Paraffin+sections+of+70-100+mum:+a+novel+technique+and+its+benefits+for+studying+the+nervous+system.">Paraffin sections of 70-100 mum: a novel technique and its benefits for studying the nervous system.</a> Journal of neuroscience methods. 215, 241-244 (2013).</li></ol>

The authors have nothing to disclose.

The overall goal of this communication was to introduce immunohistochemistry procedures to the reader. For this, the example of double-labeling with Iba1 and Pan-neuronal antigens to observe microglia and neurons in paraformaldehyde perfused, sucrose cryoprotected, cryosectioned rat brain was used.
This technique can be adapted to serve endless purposes. An array of different antigens in a variety of tissue types such as, but not limited to brain, lung, liver, kidney and intestine can be visua...

Immunohistochemistry is a process for detecting antigens (i.e. proteins) in tissue sections by using primary antibodies which bind specifically to the antigens of interest. Immunohistochemistry was pioneered by J.R. Marrack in 1934 when he determined that antibodies could localize antigens with great specificity1. Beginning in 1942, some of the first in vitro studies using fluorescent antibodies to visualize immunohistochemistry were published2,3, after which the first in vivo histochemical study was published 4. During the 1960&#8217;s, three decades after the inception of immunohistochemical methods, enzyme-conjugated antibodies began to be used as secondary reagents. These methods were simultaneously and independently developed in France and the U.S.5,6. Today, a wide array of antibodies provides endless possibilities for immunohistochemistry studies7.
The overall goal of this correspondence is to provide a brief introduction into immunohistochemical staining; it is not meant to be a comprehensive and exhaustive review of this technique. In the method outlined, immunohistochemical techniques for two antigens are presented (markers for microglia and neurons) for staining of paraformaldehyde perfused, sucrose cryoprotected, cryosectioned rat brain. Immunohistochemical staining begins with blocking nonspecific antigen binding to reduce background staining. Next, incubation with primary antibody allows for binding to a specific antigen in the tissue. Following the primary antibody, another antibody, termed secondary antibody, is applied to link the primary antibody to a conjugated visualization signal8. The secondary antibody targets the immunoglobulin G (IgG) domain specific to the species in which the primary antibody was raised. The secondary antibody amplifies the signal of the primary antibody since the Fab regions of the secondary antibody bind to multiple sites on the IgG domain of the primary antibody. Either enzymes or fluorescent molecules conjugated to the Fc regions of the secondary antibody enable visualization. For example, a rabbit anti-Iba1 primary antibody is a rabbit IgG molecule specific for Iba1. When donkey anti-rabbit IgG is applied as a secondary antibody, it will recognize and bind to multiple regions of the rabbit anti-Iba1 IgG (see Figure 1). The donkey antibody can be visualized by various methods. This correspondence focuses on detection of a fluorophore conjugated to the secondary antibody, which recognizes the primary antibody, for visualization by fluorescent microscopy. In fluorescent immunohistochemistry, a nuclear stain such as Hoechst or DAPI can be used to visualize all nuclei.
<img alt="Figure 1" src="/files/ftp_upload/52293/52293fig1highres.jpg" /> 
Figure 1: Schematic representation of direct vs. indirect antibody labeling techniques. Antibodies bind to the antigen of interest and can be amplified by secondary antibodies raised against the species of the primary antibodies. This technique can be performed using avidin-biotin complex (ABC) for amplification and DAB for visualization (A), or a directly conjugated fluorescent secondary antibody (B). Alternatively, primary antibodies can be directly conjugated with many different tags, including biotin or a fluorophore (C). <a href="https://www.jove.com/files/ftp_upload/52293/52293fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
An alternative method for visualization of immunohistochemical staining uses 3,3&#39;-diaminobenzidine tetrahydrochloride (DAB; see Figures 1 and 2). This differs from fluorescence by using a biotinylated or horse-radish peroxidase (HRP) conjugated secondary antibody, which provides an enzyme to convert DAB to a precipitate that is visible under bright field microscopy. In instances where a single antigen is of interest or staining is required to be long lasting, DAB may be more appropriate than fluorescent staining. However, DAB staining is not well-suited for differentiation between multiple markers, especially if two nuclear antigens are of interest. For information on DAB materials and protocol modifications, consult Table 1. Alternately, nitro blue tetrazolium chloride/5-Bromo-4-chloro-3-indolyl phosphate (NBT/BCIP) can be used to visualize an alkaline phosphatase (AP) conjugated secondary antibody.
<img alt="Figure 2" src="/files/ftp_upload/52293/52293fig2highres.jpg" /> 
Figure 2: Representative images of nickel-enhanced DAB single-labeled rat brain tissue sections. Rat brain sections which are labeled with nickel-enhanced DAB for Iba1 (A) and Pan-neuronal (B) allow for long-lasting analysis of microglia or neurons alone. Scale bar 20 &#181;m. <a href="https://www.jove.com/files/ftp_upload/52293/52293fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
One must consider the estimated abundance of the antigen of interest within the tissue being analyzed. Indirect methods (as described above) are useful for targets with low abundance. When the antigen of interest is in high abundance, direct methods can be applied. Direct methods involve a primary antibody that is directly conjugated to a visualization signal, and thus no secondary antibody is required. This method simplifies the staining process, but eliminates the amplification achieved by indirect methods. Using a directly conjugated primary antibody also eliminates cross-reactivity of secondary antibodies when double-labeling.
This communication details the protocol for double-labeling with Iba1 and Pan-neuronal (details in Table 1). Iba1 stains microglia in many activation states, including ramified, hyper-ramified, activated, amoeboid, and rod. Pan-neuronal stains neuronal axons, dendrites, and soma. Since Iba1 stains most microglia and Pan-neuronal targets the neuron, this combination of stains is useful in gaining a broad understanding of microglia-neuron interactions.
In sum, immunohistochemical staining relies on the careful selection of antibodies. As the research question becomes more specific, antibodies raised to alternate antigens may be desired. To target a specific microglial activation state, one may elect to use CD45 or CD68 antibodies, rather than Iba1. Further, in working with mice, F4/80 may provide the necessary results. Similarly, neuronal elements can be specifically targeted with antibodies raised against the nucleus, synapse (pre- or post-), axon, and growth cone. Additionally, there are other markers which differentiate the age of the neuron (Double-cortin, NeuN), and neuronal regeneration (GAP-43).

<table border="0" cellpadding="0" cellspacing="0" width="1171">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:399px;">Name of Material/ Equipment</td>
			<td style="width:132px;">Company</td>
			<td style="width:119px;">Catalog Number</td>
			<td style="width:523px;">Comments/Description</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Fisherbrand Superfrost Plus Glass Slides&#160;</td>
			<td>Fisher Scientific</td>
			<td>22-034-979</td>
			<td>Used for tissue mounting (1.2.2)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:399px;">Oven</td>
			<td style="width:132px;">Thermo Scientific</td>
			<td style="width:119px;">51028112</td>
			<td>Used for tissue drying (2.1.1)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:399px;">Mini Pap pen</td>
			<td style="width:132px;">Life Technologies</td>
			<td style="width:119px;">00-8877</td>
			<td>Used in step 2.2.2</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:399px;">Andwin Scientific Tissue-tek Slide Staining Dish</td>
			<td style="width:132px;">Fisher Scientific</td>
			<td style="width:119px;">22-149-429</td>
			<td>Used for all washes during staining (2.2), as well as the Hoechst step (2.2.8)&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:399px;">Kimwipes</td>
			<td style="width:132px;">Fisher Scientific</td>
			<td style="width:119px;">06-666-A</td>
			<td>Used for drying slides (2.2)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:399px;">Black Staining Box</td>
			<td style="width:132px;">Ted Pella</td>
			<td style="width:119px;">21050</td>
			<td>Used for blocking and staining steps (2.2)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:399px;">Normal Donkey Serum</td>
			<td style="width:132px;">Fisher Scientific</td>
			<td style="width:119px;">50-413-253</td>
			<td>Used for block and antibody incubation (2.2)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:399px;">Mouse &#945;-Pan-neuronal</td>
			<td style="width:132px;">Millipore</td>
			<td style="width:119px;">MAB2300</td>
			<td>Used for primary antibody (2.2.4)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:399px;">Rabbit &#945;-Iba1</td>
			<td style="width:132px;">Wako Chemical</td>
			<td style="width:119px;">019-19741</td>
			<td>Used for primary antibody (2.2.4)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:399px;">Donkey &#945;-Rabbit 594</td>
			<td style="width:132px;">Jackson ImmunoResearch</td>
			<td style="width:119px;">711-585-152</td>
			<td>Used for secondary antibody (2.2.6)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:399px;">Donkey &#945;-mouse 488</td>
			<td style="width:132px;">Jackson ImmunoResearch</td>
			<td style="width:119px;">715-545-150</td>
			<td>Used for secondary antibody (2.2.6)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:399px;">Caterer&#39;s foil</td>
			<td style="width:132px;">Any</td>
			<td style="width:119px;">N/A</td>
			<td>Used in steps 1.2.2 and 2.3.2</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:399px;">Fluoromount-G</td>
			<td style="width:132px;">Southern Biotech</td>
			<td style="width:119px;">0100-01</td>
			<td>Used for coverslipping (2.2.8)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:399px;">Coverslips</td>
			<td style="width:132px;">Fisher Scientific</td>
			<td style="width:119px;">12544E</td>
			<td>Used for coverslipping (2.2.8)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:399px;">Clear Nail Polish&#160;</td>
			<td style="width:132px;">Any</td>
			<td style="width:119px;">N/A</td>
			<td>Used for coverslipping (2.2.8)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:399px;">Axio Observer.Z1 and LSM 710 (laser scanning, confocal)</td>
			<td style="width:132px;">Carl Zeiss</td>
			<td style="width:119px;">N/A</td>
			<td>Used for imaging (3)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:399px;">Axioskop A2</td>
			<td style="width:132px;">Carl Zeiss</td>
			<td style="width:119px;">N/A</td>
			<td>Used for imaging (3)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:399px;"></td>
			<td style="width:132px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">CitriSolv&#160;</td>
			<td>FisherScientific</td>
			<td></td>
			<td>For DAB protocol</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">ABC</td>
			<td>Vector Laboratories</td>
			<td>PK-6100</td>
			<td>For DAB protocol</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">DAB Peroxidase kit</td>
			<td>Vector Laboratories</td>
			<td>SK-4100</td>
			<td>For DAB protocol</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Biotinylated horse &#945;-rabbit IgG</td>
			<td>Vector Laboratories</td>
			<td>BA-1100</td>
			<td>For DAB protocol</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Biotinylated horse &#945;-mouse IgG</td>
			<td>Vector Laboratories</td>
			<td>BA-2001</td>
			<td>For DAB protocol</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">30% Hydrogen Peroxide</td>
			<td>FisherScientific</td>
			<td>H325-500</td>
			<td>For DAB protocol</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:399px;">Wheaton slide racks and staining dishes</td>
			<td style="width:132px;">TedPella</td>
			<td style="width:119px;">21043</td>
			<td>For DAB protocol</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:399px;"></td>
			<td style="width:132px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Masterflex perfusion pump and tubing</td>
			<td>Cole-Parmer</td>
			<td></td>
			<td>Used for perfusion (1.1.1 and 1.1.2)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Andwin scientific tissue-tek CRYO-OCT compound (case of 12)</td>
			<td>Fisher Scientific</td>
			<td>14-373-65</td>
			<td>Used for tissue freezing (1.2.1)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:399px;">Thermometer (-50 to 50 C)&#160;</td>
			<td style="width:132px;">Fisher Scientific</td>
			<td style="width:119px;">15-059-228</td>
			<td>Used for tissue freezing (1.2.1)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cryostat</td>
			<td>Leica&#160;</td>
			<td>CM3500S</td>
			<td>Used for tissue sectioning (1.2.2)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:399px;"></td>
			<td style="width:132px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Staining Dish, Plastic with 2 Lids</td>
			<td>Grale Scientific</td>
			<td>353</td>
			<td>For antigen retrival</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">20 Place Staining Rack, Slides Horizontal</td>
			<td>Grale Scientific</td>
			<td>354</td>
			<td>For antigen retrival</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Microwave</td>
			<td>Any</td>
			<td>N/A</td>
			<td>For antigen retrival</td>
		</tr>
	</tbody>
</table>

primer for immunohistochemistry on cryosectioned rat brain tissue: example staining for microglia and neurons

Immunohistochemistry is a widely used technique for detecting the presence, location, and relative abundance of antigens in situ. This introductory level protocol describes the reagents, equipment, and techniques required to complete immunohistochemical staining of rodent brain tissue, using markers for microglia and neuronal elements as an example. Specifically, this paper is a step-by-step protocol for fluorescent visualization of microglia and neurons via immunohistochemistry for Iba1 and Pan-neuronal, respectively. Fluorescence double-labeling is particularly useful for the localization of multiple proteins within the same sample, providing the opportunity to accurately observe interactions between cell types, receptors, ligands, and/or the extracellular matrix in relation to one another as well as protein co-localization within a single cell. Unlike other visualization techniques, fluorescence immunohistochemistry staining intensity may decrease in the weeks to months following staining, unless appropriate precautions are taken. Despite this limitation, in many applications fluorescence double-labeling is preferred over alternatives such as 3,3&#39;-diaminobenzidine tetrahydrochloride (DAB) or alkaline phosphatase (AP), as fluorescence is more time efficient and allows for more precise differentiation between two or more markers. The discussion includes troubleshooting tips and advice to promote success.

This staining protocol results in rat brain tissue sections that have microglia fluorescently labeled in the 594 channel (red) and neurons labeled in the 488 channel (green; see Figure 4). If a nuclear stain has been done, it will show in the 405 channel (blue). Images can be taken in different channels and overlaid for direct comparison of the three channels, or between any two channels. Many digital acquisition software suites include this functionality. Double-labeling with Iba1 and Pan-neuronal marke...

Watch this Scientific Journal Video about Primer for Immunohistochemistry on Cryosectioned Rat Brain Tissue: Example Staining for Microglia and Neurons at JoVE.com

Primer for Immunohistochemistry on Cryosectioned Rat Brain Tissue: Example Staining for Microglia and Neurons

This introductory level protocol describes the reagents, equipment, and techniques required to complete immunohistochemical staining of rodent brains, using markers for microglia and neuronal elements as an example.

Immunohistochemistry is a widely used technique for detecting the presence, location, and relative abundance of antigens in situ. This introductory level ...

primer-for-immunohistochemistry-on-cryosectioned-rat-brain-tissue

Research

JoVE Journal

Neuroscience

31.5K Views.  University of Arizona College of Medicine - Phoenix. This introductory level protocol describes the reagents, equipment, and techniques required to complete immunohistochemical staining of rodent brains, using markers for microglia and neuronal elements as an example. 