Name: fast and specific assessment of the halogenating peroxidase activity in leukocyte-enriched blood samples
Uploaded: 2016-07-28T15:00:00
Description: Watch this Scientific Journal Video about Fast and Specific Assessment of the Halogenating Peroxidase Activity in Leukocyte-enriched Blood Samples at JoVE.com

This work was made possible by funding from the German Federal Ministry of Education and Research (BMBF, 1315883) as well as by the S&#228;chsische Aufbaubank (SAB) project 100116526 from a funding of the European Regional Development Fund (ERDF).

All human blood samples were obtained from healthy volunteers, and the applied leukocyte enrichment protocol follows the guidelines of ethics commission of the Medical Faculty of the University of Leipzig. The experiments with rat blood were approved by the responsible local ethical committee (Landesdirektion Sachsen, Referat 24), according to the German guidelines on animal care and use.
1. Experimental Setup
NOTE: As the hypotonic lysis procedure for the depletion o...

As neutrophils are the most abundant leukocytes in human blood the isolation of peroxidase-positive cells often only focuses on these cells and includes a separation of neutrophils from other leukocytes by density gradient centrifugation38. Yet as neutrophils are much less abundant in murine blood samples39 for the latter more complicated methods have to be used40. Moreover both methods also lead to the removal of peroxidase-positive monocytes from the samples and, due to the need of larg...

Polymorphonuclear leukocytes (PMNs, also called granulocytes) and monocytes represent important cellular components of the innate immune system in the blood1,2. They contribute to the primary defense against pathogens as well as to the activation of the acquired immune system and the initiation of a systemic inflammatory response2-4. Yet especially neutrophils, the most abundant type of granulocytes, and monocytes also significantly contribute to the regulation and termination of acute inflammatory events5. Therefore these cells may also play an important role in chronic inflammatory diseases like rheumatoid arthritis6,7. In fact, asthma, a chronic inflammatory airway disease, is characterized by an impaired apoptosis of eosinophils, the second most granulocyte type in the blood8. Yet the apoptosis of granulocytes and their quick removal by macrophages are two essential steps during the cellular termination of inflammation9-11.
In the named immune cells two closely related enzymes, namely myeloperoxidase (MPO, neutrophils and monocytes) and eosinophil peroxidase (EPO, eosinophils) can be found12,13. These heme peroxidases are classically related to the humoral immune response as they two-electronically oxidize (pseudo-)halides to the corresponding hypo(pseudo)halous acids which are known for their bactericidal properties14-16. Under physiological conditions MPO mainly forms hypochlorous acid (HOCl) and hypothiocyanite (-OSCN) while the latter and hypobromous acid (HOBr) are formed by EPO17-19. New results suggest that this (pseudo-)halogenating enzyme activity may also contribute to the regulation of inflammatory responses and to the termination of immune reactions20,21. In fact, the HOCl production by MPO and derived products were shown to suppress T cell-based adaptive immune responses22-24.
In order to gain more insights into the immunological role of leukocytes from the innate immune system at chronic inflammatory diseases and to determine the contribution of MPO and EPO to this physiological function we developed a method to quickly enrich leukocytes from small blood samples for a subsequent specific determination of the halogenating peroxidase activity in these cells. For erythrocyte depletion we have chosen a standardized method including two-subsequent hypotonic lysis steps with distilled water, which leads to a quick leukocyte enrichment at low material costs. For the subsequent determination of the halogenating MPO and EPO activity the HOCl- and HOBr-specific dye aminophenyl fluorescein (APF) was used25-27. In contrast to the application of unspecific peroxidase staining methods28,29, this approach allows the selective detection of the halogenating peroxidase activity, which is often impaired at severe inflammation30,31.

<table border="0" cellpadding="0" cellspacing="0" width="738">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:213px;">materials/equipment</td>
			<td style="width:203px;"></td>
			<td style="width:120px;"></td>
			<td style="width:203px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:213px;">15 ml centrifugation tubes</td>
			<td style="width:203px;">VWR/Corning</td>
			<td style="width:120px;">734-0451</td>
			<td style="width:203px;">-</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:213px;">1.5 ml sample tubes</td>
			<td style="width:203px;">VWR/Eppendorf</td>
			<td style="width:120px;">211-2130DE</td>
			<td style="width:203px;">-</td>
		</tr>
		<tr height="105">
			<td height="105" style="height:105px;width:213px;">Pipettes for volumes up to 5 ml</td>
			<td style="width:203px;">Eppendorf</td>
			<td style="width:120px;">e.g. 3120000070</td>
			<td style="width:203px;">We are using Eppendorf Resarch plus pipettes with adjustable volumes in the range 1-10 &#181;l, 10-100&#181;l, 100-1000 &#181;l an 500-5000&#181;l</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:213px;">laminar flow bench</td>
			<td style="width:203px;">Thermo Electron Corperation</td>
			<td style="width:120px;">HeraSafe</td>
			<td style="width:203px;">-</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:213px;">Vortex mixer</td>
			<td style="width:203px;">Bender &#38; Hobein AG</td>
			<td style="width:120px;">Vortex Genie 2</td>
			<td style="width:203px;">-</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">Tabletop centrifuge</td>
			<td style="width:203px;">Kendro Laboratory Products</td>
			<td style="width:120px;">Laborfuge 400R</td>
			<td style="width:203px;">The centrifuge should be able to be used at 450x g</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">Small centrifuge</td>
			<td style="width:203px;">eppendorf</td>
			<td style="width:120px;">5415D</td>
			<td style="width:203px;">The centrifuge should be able to be used at 400x g</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">Incubator</td>
			<td style="width:203px;">Heraeus</td>
			<td style="width:120px;">cytoperm 2</td>
			<td style="width:203px;">Settings: 37 &#176;C, 95% humidity, 5 % CO2 content</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;">UV-Vis spectrophotometer</td>
			<td style="width:203px;">Varian</td>
			<td style="width:120px;">Cary 50 bio</td>
			<td style="width:203px;">A spectrum between 200 and 300 nm has to be recorded. Thus quartz cuvettes have to be applied</td>
		</tr>
		<tr height="105">
			<td height="105" style="height:105px;">Flow cytometer</td>
			<td style="width:203px;">Becton, Dickinson</td>
			<td style="width:120px;">BD Facs Calibur</td>
			<td style="width:203px;">Any flow cytometer can be used which is equiped with a laser suitable for the excitation of fluorescein (e.g 488 nm argon laser)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Name</td>
			<td style="width:203px;">Company</td>
			<td style="width:120px;">Catalog Number</td>
			<td style="width:203px;">Comments</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:213px;">Chemicals</td>
			<td style="width:203px;"></td>
			<td style="width:120px;"></td>
			<td style="width:203px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:213px;">Phosphate buffered saline (PBS)</td>
			<td style="width:203px;">amresco</td>
			<td style="width:120px;">K812</td>
			<td style="width:203px;">sterile solution, ready to use</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:213px;"></td>
			<td style="width:203px;">Sigma-Aldrich</td>
			<td style="width:120px;">P4417</td>
			<td style="width:203px;">tablets for solving in 200 ml millipore water</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:213px;">Hanks balanced salt solution (HBSS) with Ca(2+)</td>
			<td style="width:203px;">Sigma-Aldrich</td>
			<td style="width:120px;">H1387</td>
			<td style="width:203px;">970 mg/100 ml, carefully check and adjust the pH value to 7.4</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:213px;">Hydrochloric acid</td>
			<td style="width:203px;">Merck Millipore</td>
			<td style="width:120px;">1.09057.1000</td>
			<td style="width:203px;">1M solution</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:213px;">Sodium hydroxide</td>
			<td style="width:203px;">Riedel-deHa&#235;n</td>
			<td style="width:120px;">30620</td>
			<td style="width:203px;">Solid pellets. For a 1M solution solve 4 g/100 ml Millipore water</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:213px;">Aminophenyl fluorescein</td>
			<td style="width:203px;">Cayman</td>
			<td style="width:120px;">10157</td>
			<td style="width:203px;">5 mg/ml solution (11.81 mM) in methyl acetate, aliquotes of e.g. 100 &#181;l should be prepared and stored at -20 &#176;C</td>
		</tr>
		<tr height="168">
			<td height="168" style="height:168px;width:213px;">Hydrogen peroxide</td>
			<td style="width:203px;">Sigma-Aldrich</td>
			<td style="width:120px;">H1009</td>
			<td style="width:203px;">This 30% stock solution corresponds to a concentration of about 8.8 M. Further dilutions have to be freshly prepared in distilled water immediately prior to use and quantified by absorbance measurements</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:213px;">4-aminobenzoic acid hydrazide (4-ABAH)</td>
			<td style="width:203px;">Sigma-Aldrich</td>
			<td style="width:120px;">A41909</td>
			<td style="width:203px;">A first stock solution of 1 M should be prepared in DMSO a second one of 100 mM by 1:10 dilution in HBSS</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:213px;">DMSO</td>
			<td style="width:203px;">VWR chemicals</td>
			<td style="width:120px;">23500.26</td>
			<td style="width:203px;">-</td>
		</tr>
	</tbody>
</table>

fast and specific assessment of the halogenating peroxidase activity in leukocyte-enriched blood samples

In this paper a protocol for the quick and standardized enrichment of leukocytes from small whole blood samples is described. This procedure is based on the hypotonic lysis of erythrocytes and can be applied to human samples as well as to blood of non-human origin. The small initial sample volume of about 50 to 100 &#181;l makes this method applicable to recurrent blood sampling from small laboratory animals. Moreover, leukocyte enrichment is achieved within minutes and with low material efforts regarding chemicals and instrumentation, making this method applicable in multiple laboratory environments.
Standardized purification of leukocytes is combined with a highly selective staining method to evaluate halogenating peroxidase activity of the heme peroxidases, myeloperoxidase (MPO) and eosinophil peroxidase (EPO), i.e., the formation of hypochlorous and hypobromous acid (HOCl and HOBr). While MPO is strongly expressed in neutrophils, the most abundant immune cell type in human blood as well as in monocytes, the related enzyme EPO is exclusively expressed in eosinophils. The halogenating activity of these enzymes is addressed by using the almost HOCl- and HOBr-specific dye aminophenyl fluorescein (APF) and the primary peroxidase substrate hydrogen peroxide. Upon subsequent flow cytometry analysis all peroxidase-positive cells (neutrophils, monocytes, eosinophils) are distinguishable and their halogenating peroxidase activity can be quantified. Since APF staining may be combined with the application of cell surface markers, this protocol can be extended to specifically address leukocyte sub-fractions. The method is applicable to detect HOCl and HOBr production both in human and in rodent leukocytes.
Given the widely and diversely discussed immunological role of these enzymatic products in chronic inflammatory diseases, this protocol may contribute to a better understanding of the immunological relevance of leukocyte-derived heme peroxidases.

As reported previously the method described above turned out to be applicable both to human and to non-human material32. Moreover as shown for mice with asthmatic symptoms the APF staining may be a suitable tool to detect differences in the systemic pro-inflammatory status. Therefore in a subsequent study we used this protocol to repeatedly evaluate the halogenating activity of MPO (and EPO) in female Dark Agouti rats with pristane-induced arthritis (PIA). A representa...

Watch this Scientific Journal Video about Fast and Specific Assessment of the Halogenating Peroxidase Activity in Leukocyte-enriched Blood Samples at JoVE.com

Fast and Specific Assessment of the Halogenating Peroxidase Activity in Leukocyte-enriched Blood Samples

This protocol describes the quick enrichment of leukocytes from small blood samples for a subsequent specific determination of the halogenating peroxidase activity within the cells. The method can be applied to human and non-human material and may contribute to the evaluation of new inflammatory markers.

In this paper a protocol for the quick and standardized enrichment of leukocytes from small whole blood samples is described. This procedure is based on ...

The overall goal of this erythrocyte depletion method is to achieve a quick and simple leukoctye-enrichment from a small blood sample. Many advantages of this technique are that it is cheap, reliable, and fast. Moreover, it can be applied to human and non-human blood samples.Before beginning the lysis procedure, adjust the pipette for water administration to two milliliters, and the pipette for PBS to five milliliters. Then place open flasks of water and PBS under a laminar flow hood at room temperature. As the hypotonic lysis is a time-critical process, everything should be prepared previously.Moreover, the lysis proceudre should always be done in the same way, to have compatible results. Next, transfer 100 microliters from each blood sample into a 15 milliliter conical tube. And add two milliliters of distilled water to each sample with vortexing at the medium setting.Rest the cells for 60 seconds, then add five milliliters of PBS. And mix the samples by vortexing. Now, collect the cells by centrifugation, and decant the supernatants.Invert the tubes and tap the openings on a paper towel to remove as much liquid as possible. Then repeat the hypotonic lysis procedure as just demonstrated. After obtaining a dry pellet for the second time, re-suspend each sample in 500 microliters of HBSS, until a homogeneous solution is obtained.And transfer the cells into 1.5 milliliter, micro-centrifuge tubes on ice. To check the peroxidase specificity of the samples after amino phenol fluorescein, or APF staining, first add five microliters of the heme peroxidase inhibitor, 4-ABAH, to the appropriate samples for a 15 minute incubation at 37 degrees Celsius. Next, add five microliters of APF working solution to each tube, and gently vortex the cells on the medium setting.Incubate all of the samples at 37 degrees Celsius for 30 minutes. Then add five microliters of hydrogen peroxide working solution to each sample, and gently vortex the tubes. After 60 minutes at 37 degrees Celsius, centrifuge the cells, and carefully remove the supernatant without disturbing the pellets.Finally, re-suspend the cells in 250 microliters of HBSS, and store the samples in the dark until their analysis, to avoid photo bleaching. Here, a representative example of the leukocyte populations after hypotonic lysis and APF staining as just demonstrated is shown. By plotting cell size versus granularity, the robust depletion of the erythrocytes can be observed, with the red blood cell and debris population accounting for only 22%of the events.Further, the intensity distribution of the APF-derived fluorescence facilitates a clear discrimination of the peroxidase-negative erythrocites and lymphocytes, with a moderate APF oxidation observed, for the peroxidase-positive monocytes and eosinophils, and a robust peroxidase oxidation exhibited by the neutrophils. Once mastered, this technique can be applied to up to 50 blood samples in parallel if it is performed properly. Following this procedure, other methods like antibody staining can be performed to identify the cell subsets of interest.After its development, this technique paved the way for researchers in the field of small animal studies to explore the role of halogenating activity of MPO and EPO in animal models for chronic inflammatory diseases.

fast-specific-assessment-halogenating-peroxidase-activity-leukocyte

Research

JoVE Journal

Immunology and Infection

Depletion of Specific Cell Populations by Complement Depletion

The purification of immune cell populations is often required in order to study their unique functions. In particular, molecular approaches such as real-time PCR and microarray analysis require the isolation of cell populations with high purity. Commonly used purification strategies include fluorescent activated cell sorting (FACS), magnetic bead separation and complement depletion. Of the three strategies, complement depletion offers the advantages of being fast, inexpensive, gentle on the cells and a high cell yield. The complement system is composed of a large number of plasma proteins that when activated initiate a proteolytic cascade culminating in the formation of a membrane-attack complex that forms a pore on a cell surface resulting in cell death1. The classical pathway is activated by IgM and IgG antibodies and was first described as a mechanism for killing bacteria. With the generation of monoclonal antibodies (mAb), the complement cascade can be used to lyse any cell population in an antigen-specific manner. Depletion of cells by the complement cascade is achieved by the addition of complement fixing antigen-specific antibodies and rabbit complement to the starting cell population. The cells are incubated for one hour at 37&deg;C and the lysed cells are subsequently removed by two rounds of washing. MAb with a high efficiency for complement fixation typically deplete 95-100% of the targeted cell population. Depending on the purification strategy for the targeted cell population, complement depletion can be used for cell purification or for the enrichment of cell populations that then can be further purified by a subsequent method.

To effectively study the function of immune cell populations their purification is often required. Complement depletion is a fast and inexpensive technique for the isolation of immune cell populations with high purity.

The purification of immune cell populations is often required in order to study their unique functions.  In particular, molecular approaches such as ...

Purification of Specific Cell Population by Fluorescence Activated Cell Sorting (FACS)

Experimental and clinical studies often require highly purified cell populations.  FACS is a technique of choice to purify cell populations of known phenotype.  Other bulk methods of purification include panning, complement depletion and magnetic bead separation.  However, FACS has several advantages over other available methods.  FACS is the preferred method when very high purity of the desired population is required, when the target cell population expresses a very low level of the identifying marker or when cell populations require separation based on differential marker density.  In addition, FACS is the only available purification technique to isolate cells based on internal staining or intracellular protein expression, such as a genetically modified fluorescent protein marker.  FACS allows the purification of individual cells based on size, granularity and fluorescence.  In order to purify cells of interest, they are first stained with fluorescently-tagged monoclonal antibodies (mAb), which recognize specific surface markers on the desired cell population (1).  Negative selection of unstained cells is also possible.  FACS purification requires a flow cytometer with sorting capacity and the appropriate software.  For FACS, cells in suspension are passed as a stream in droplets with each containing a single cell in front of a laser.  The fluorescence detection system detects cells of interest based on predetermined fluorescent parameters of the cells.  The instrument applies a charge to the droplet containing a cell of interest and an electrostatic deflection system facilitates collection of the charged droplets into appropriate collection tubes (2).  The success of staining and thereby sorting depends largely on the selection of the identifying markers and the choice of mAb.  Sorting parameters can be adjusted depending on the requirement of purity and yield.  Although FACS requires specialized equipment and personnel training, it is the method of choice for isolation of highly purified cell populations.

Purification of Specific Cell Population by Fluorescence Activated Cell Sorting FACS

For many scientific studies requiring a biological and chemical analysis of cell populations the cells must be in a high state of purity. Fluorescence activated cell sorting (FACS) is a superior method in which to obtain pure cell populations.

Experimental and clinical studies often require highly purified cell populations.  FACS is a technique of choice to purify cell populations of known ...

Introducing Shear Stress in the Study of Bacterial Adhesion

During bacterial infections a sequence of interactions occur between the pathogen and its host. Bacterial adhesion to the host cell surface is often the initial and determining step of the pathogenesis. Although experimentally adhesion is mostly studied in static conditions adhesion actually takes place in the presence of flowing liquid. First encounters between bacteria and their host often occur at the mucosal level, mouth, lung, gut, eye, etc. where mucus flows along the surface of epithelial cells. Later in infection, pathogens occasionally access the blood circulation causing life-threatening illnesses such as septicemia, sepsis and meningitis. A defining feature of these infections is the ability of these pathogens to interact with endothelial cells in presence of circulating blood. The presence of flowing liquid, mucus or blood for instance, determines adhesion because it generates a mechanical force on the pathogen. To characterize the effect of flowing liquid one usually refers to the notion of shear stress, which is the tangential force exerted per unit area by a fluid moving near a stationary wall, expressed in dynes/cm2. Intensities of shear stress vary widely according to the different vessels type, size, organ, location etc. (0-100 dynes/cm2). Circulation in capillaries can reach very low shear stress values and even temporarily stop during periods ranging between a few seconds to several minutes 1. On the other end of the spectrum shear stress in arterioles can reach 100 dynes/cm2 2. The impact of shear stress on different biological processes has been clearly demonstrated as for instance during the interaction of leukocytes with the endothelium 3. To take into account this mechanical parameter in the process of bacterial adhesion we took advantage of an experimental procedure based on the use of a disposable flow chamber 4. Host cells are grown in the flow chamber and fluorescent bacteria are introduced in the flow controlled by a syringe pump. We initially focused our investigations on the bacterial pathogen Neisseria meningitidis, a Gram-negative bacterium responsible for septicemia and meningitis. The procedure described here allowed us to study the impact of shear stress on the ability of the bacteria to: adhere to cells 1, to proliferate on the cell surface 5and to detach to colonize new sites 6 (Figure 1). Complementary technical information can be found in reference 7. Shear stress values presented here were chosen based on our previous experience1 and to represent values found in the literature. The protocol should be applicable to a wide range of pathogens with specific adjustments depending on the objectives of the study.

During the infection process, a key step is the adhesion of pathogens with host cells. In most instances this adhesion step occurs in the presence of mechanical stress generated by flowing liquid. We describe a technique that introduces shear stress as an important parameter in the study of bacterial adhesion.

During bacterial infections a sequence of interactions occur between the pathogen and its host. Bacterial adhesion to the host cell surface is often the ...

Determining the Phagocytic Activity of Clinical Antibody Samples

Antibody-driven phagocytosis is induced via the engagement of Fc receptors on professional phagocytes, and can contribute to both clearance as well as pathology of disease. While the properties of the variable domains of antibodies have long been considered critical to in vivo function, the ability of antibodies to recruit innate immune cells via their Fc domains has become increasingly appreciated as a major factor in their efficacy, both in the setting of recombinant monoclonal antibody therapy, as well as in the course of natural infection or vaccination1-3.
Importantly, despite its nomenclature as a constant domain, the antibody Fc domain does not have constant function, and is strongly modulated by IgG subclass (IgG1-4) and glycosylation at Asparagine 2974-6. Thus, this method to study functional differences of antigen-specific antibodies in clinical samples will facilitate correlation of the phagocytic potential of antibodies to disease state, susceptibility to infection, progression, or clinical outcome.
Furthermore, this effector function is particularly important in light of the documented ability of antibodies to enhance infection by providing pathogens access into host cells via Fc receptor-driven phagocytosis7. Additionally, there is some evidence that phagocytic uptake of immune complexes can impact the Th1/Th2 polarization of the immune response8.
Here, we describe an assay designed to detect differences in antibody-induced phagocytosis, which may be caused by differential IgG subclass, glycan structure at Asn297, as well as the ability to form immune complexes of antigen-specific antibodies in a high-throughput fashion. To this end, 1 &mu;m fluorescent beads are coated with antigen, then incubated with clinical antibody samples, generating fluorescent antigen specific immune complexes. These antibody-opsonized beads are then incubated with a monocytic cell line expressing multiple Fc&gamma;Rs, including both inhibitory and activating. Assay output can include phagocytic activity, cytokine secretion, and patterns of Fc&gamma;Rs usage, and are determined in a standardized manner, making this a highly useful system for parsing differences in this antibody-dependent effector function in both infection and vaccine-mediated protection9.

We present a high-throughput flow cytometric assay to determine the phagocytic activity of antigen-specific antibodies from clinical samples, utilizing fluorescent antigen-coated beads and a monocytic cell line expressing multiple Fc receptors&#x2014;providing receptor usage and phagocytic activity determinations in a standardized and reproducible fashion for any antigen of interest.

Antibody-driven phagocytosis is induced via the engagement of Fc receptors on professional phagocytes, and can contribute to both clearance as well as ...

Quantitative Imaging of Lineage-specific Toll-like Receptor-mediated Signaling in Monocytes and Dendritic Cells from Small Samples of Human Blood

Individual variations in immune status determine responses to infection and contribute to disease severity and outcome. Aging is associated with an increased susceptibility to viral and bacterial infections and decreased responsiveness to vaccines with a well-documented decline in humoral as well as cell-mediated immune responses1,2. We have recently assessed the effects of aging on Toll-like receptors (TLRs), key components of the innate immune system that detect microbial infection and trigger antimicrobial host defense responses3. In a large cohort of healthy human donors, we showed that peripheral blood monocytes from the elderly have decreased expression and function of certain TLRs4 and similar reduced TLR levels and signaling responses in dendritic cells (DCs), antigen-presenting cells that are pivotal in the linkage between innate and adaptive immunity5. We have shown dysregulation of TLR3 in macrophages and lower production of IFN by DCs from elderly donors in response to infection with West Nile virus6,7. 
Paramount to our understanding of immunosenescence and to therapeutic intervention is a detailed understanding of specific cell types responding and the mechanism(s) of signal transduction. Traditional studies of immune responses through imaging of primary cells and surveying cell markers by FACS or immunoblot have advanced our understanding significantly, however, these studies are generally limited technically by the small sample volume available from patients and the inability to conduct complex laboratory techniques on multiple human samples. ImageStream combines quantitative flow cytometry with simultaneous high-resolution digital imaging and thus facilitates investigation in multiple cell populations contemporaneously for an efficient capture of patient susceptibility. Here we demonstrate the use of ImageStream in DCs to assess TLR7/8 activation-mediated increases in phosphorylation and nuclear translocation of a key transcription factor, NF-&kappa;B, which initiates transcription of numerous genes that are critical for immune responses8. Using this technology, we have also recently demonstrated a previously unrecognized alteration of TLR5 signaling and the NF-&kappa;B pathway in monocytes from older donors that may contribute to altered immune responsiveness in aging9.

We describe use of ImageStream technology (<a href="http://www.amnis.com/" target="_blank">www.amnis.com</a>), which combines quantitative flow cytometry with simultaneous high-resolution digital imaging, to quantify cellular mechanisms of primary immune cells from well-defined patient cohorts. Our studies provide a blueprint for translational investigations to quantify lineage specific cellular responses in small samples from subject cohorts.

Individual variations in immune status determine responses to infection and contribute to disease severity and outcome.  Aging is associated with an ...

Generation of Human Alloantigen-specific T Cells from Peripheral Blood

The study of human T lymphocyte biology often involves examination of responses to activating ligands. T cells recognize and respond to processed peptide antigens presented by MHC (human ortholog HLA) molecules through the T cell receptor (TCR) in a highly sensitive and specific manner. While the primary function of T cells is to mediate protective immune responses to foreign antigens presented by self-MHC, T cells respond robustly to antigenic differences in allogeneic tissues. T cell responses to alloantigens can be described as either direct or indirect alloreactivity. In alloreactivity, the T cell responds through highly specific recognition of both the presented peptide and the MHC molecule. The robust oligoclonal response of T cells to allogeneic stimulation reflects the large number of potentially stimulatory alloantigens present in allogeneic tissues. While the breadth of alloreactive T cell responses is an important factor in initiating and mediating the pathology associated with biologically-relevant alloreactive responses such as graft versus host disease and allograft rejection, it can preclude analysis of T cell responses to allogeneic ligands. To this end, this protocol describes a method for generating alloreactive T cells from naive human peripheral blood leukocytes (PBL) that respond to known peptide-MHC (pMHC) alloantigens. The protocol applies pMHC multimer labeling, magnetic bead enrichment and flow cytometry to single cell in vitro culture methods for the generation of alloantigen-specific T cell clones. This enables studies of the biochemistry and function of T cells responding to allogeneic stimulation.

This article describes a method for the generation and propagation of human T cell clones that specifically respond to a defined alloantigen. This protocol can be adapted for cloning human T cells specific for a variety of peptide-MHC ligands.

The study of human T lymphocyte biology often involves examination of responses to activating ligands. T cells recognize and respond to processed peptide ...

Measuring Granulocyte and Monocyte Phagocytosis and Oxidative Burst Activity in Human Blood

The granulocyte and monocyte phagocytosis and oxidative burst (OB) activity assay can be used to study the innate immune system. This manuscript provides the necessary methodology to add this assay to an exercise immunology arsenal. The first step in this assay is to prepare two aliquots ("H" and "F") of whole blood (heparin). Then, dihydroethidium is added to the H aliquot, and both aliquots are incubated in a warm water bath followed by a cold water bath. Next, Staphylococcus aureus (S. aureus) is added to the H aliquot and fluorescein isothiocyanate-labeled S. aureus is added to the F aliquot (bacteria:phagocyte = 8:1), and both aliquots are incubated in a warm water bath followed by a cold water bath. Then, trypan blue is added to each aliquot to quench extracellular fluorescence, and the cells are washed with phosphate-buffered saline. Next, the red blood cells are lysed, and the white blood cells are fixed. Finally, a flow cytometer and appropriate analysis software are used to measure granulocyte and monocyte phagocytosis and OB activity. This assay has been used for over 20 years. After heavy and prolonged exertion, athletes experience a significant but transient increase in phagocytosis and an extended decrease in OB activity. The post-exercise increase in phagocytosis is correlated with inflammation. In contrast to normal weight individuals, granulocyte and monocyte phagocytosis is chronically elevated in overweight and obese participants, and is modestly correlated with C-reactive protein. In summary, this flow cytometry-based assay measures the phagocytosis and OB activity of phagocytes and can be used as an additional measure of exercise- and obesity-induced inflammation.

The purpose of this manuscript is to present a method for measuring monocyte and granulocyte phagocytosis and oxidative burst activity in human blood samples.

The granulocyte and monocyte phagocytosis and oxidative burst (OB) activity assay can be used to study the innate immune system. This manuscript provides ...

Flow Cytometric Analysis of Natural Killer Cell Lytic Activity in Human Whole Blood

NK cell cytotoxicity is a widely used measure to determine the effect of outside intervention on NK cell function. However, the accuracy and reproducibility of this assay can be considered unstable, either because of user&#39;s errors or because of the sensitivity of NK cells to experimental manipulation. To eliminate these issues, a workflow that reduces them to a minimum was established and is presented here. To illustrate, we obtained blood samples, at various time points, from runners (n = 4) that were submitted to an intense bout of exercise. First, NK cells are simultaneously identified and isolated through CD56 tagging and magnetic-based sorting, directly from whole blood and from as little as one milliliter. The sorted NK cells are removed of any reagent or capping antibodies. They can be counted in order to establish an accurate NK cell count per milliliter of blood. Secondly, the sorted NK cells (effectors cells or E) can be mixed with 3,3&#39;-Diotadecyloxacarbocyanine Perchlorate (DiO) tagged K562 cells (target cells or T) at an assay-optimal 1:5 T:E ratio, and analyzed using an imaging flow-cytometer that allows for the visualization of each event and the elimination of any false positive or false negatives (such as doublets or effector cells). This workflow can be completed in about 4 h, and allows for very stable results even when working with human samples. When available, research teams can test several experimental interventions in human subjects, and compare measurements across several time points without compromising the data&#39;s integrity.

This work describes an advanced workflow for the accurate and fast determination of NK (Natural Killer) cell count and NK cell cytotoxicity in human blood samples.

NK cell cytotoxicity is a widely used measure to determine the effect of outside intervention on NK cell function. However, the accuracy and ...

Dextran Enhances the Lentiviral Transduction Efficiency of Murine and Human Primary NK Cells

The efficient transduction of specific genes into natural killer (NK) cells has been a major challenge. Successful transductions are critical to defining the role of the gene of interest in the development, differentiation, and function of NK cells. Recent advances related to chimeric antigen receptors (CARs) in cancer immunotherapy accentuate the need for an efficient method to deliver exogenous genes to effector lymphocytes. The efficiencies of lentiviral-mediated gene transductions into primary human or mouse NK cells remain significantly low, which is a major limiting factor. Recent advances using cationic polymers, such as polybrene, show an improved gene transduction efficiency in T cells. However, these products failed to improve the transduction efficiencies of NK cells. This work shows that dextran, a branched glucan polysaccharide, significantly improves the transduction efficiency of human and mouse primary NK cells. This highly reproducible transduction methodology provides a competent tool for transducing human primary NK cells, which can vastly improve clinical gene delivery applications and thus NK cell-based cancer immunotherapy.

The goal of this study was to formulate technologies that allow for successful gene transduction in primary natural killer (NK) cells. The dextran-mediated lentiviral transduction of human or mouse primary NK cells results in higher gene expression efficiencies. This method of gene transduction will vastly improve NK cell genetic manipulation.

The efficient transduction of specific genes into natural killer (NK) cells has been a major challenge. Successful transductions are critical to defining ...

Magnetic Stirrer Method for the Detection of Trichinella Larvae in Muscle Samples

Trichinellosis is a debilitating disease in humans and is caused by the consumption of raw or undercooked meat of animals infected with the nematode larvae of the genus Trichinella. The most important sources of human infections worldwide are game meat and pork or pork products. In many countries, the prevention of human trichinellosis is based on the identification of infected animals by means of the artificial digestion of muscle samples from susceptible animal carcasses.
There are several methods based on the digestion of meat but the magnetic stirrer method is considered the gold standard. This method allows the detection of Trichinella larvae by microscopy after the enzymatic digestion of muscle samples and subsequent filtration and sedimentation steps. Although this method does not require special and expensive equipment, internal controls cannot be used. Therefore, stringent quality management should be applied throughout the test. The aim of the present work is to provide detailed handling instructions and critical control points of the method to analysts, based on the experience of the European Union Reference Laboratory for Parasites and the National Reference Laboratory of Germany for Trichinella.

Magnetic Stirrer Method for the Detection of Trichinella Larvae in Muscle Samples

The prevention of human trichinellosis in many countries worldwide is based on the laboratory examination of muscle samples from susceptible animals by methods of digestion, of which the magnetic stirrer method is considered the gold standard.

Trichinellosis is a debilitating disease in humans and is caused by the consumption of raw or undercooked meat of animals infected with the nematode ...