The purpose of this manuscript is to present a method for measuring monocyte and granulocyte phagocytosis and oxidative burst activity in human blood samples.
Method Article
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 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 granulocyte and monocyte phagocytosis/oxidative burst (OB) activity assay is a simple, straight-forward technique that is frequently used to gather information about innate immune function following prolonged and intensive exercise.1-4 When studying the response of the immune system to a stimulus, granulocytes and monocytes are of particular interest because they play a central role in host defense and are the first immune cells to accumulate at the site of infection.5 Neutrophils, a type of granulocyte, are the first cells to translocate into damaged muscle tissue following intensive exercise.6 Phagocytosis and OB activity are the most common measures of granulocyte and monocyte function,7 and are preferred as indicators of innate immune cell function because of their central role in both the infection process and the repair process.
The assay described in this manuscript utilizes a basic flow cytometer to provide a quantitative determination of granulocyte and monocyte phagocytosis and OB activity in whole blood. The use of whole blood in this technique is advantageous because it allows the assay to be conducted without a time-consuming purification procedure. This assay can easily be modified to accommodate a variety of research designs and lab capabilities. For example, Liao et al. utilized a similar technique to show that neutrophil OB activity is increased and neutrophil phagocytosis is decreased following traumatic brain injury.8 In another example, McFarlin et al. described an elegant modification of this technique that uses allophycocyanin (APC)-conjugated CD66b and high-performance tandem APC-conjugated CD45 labeling with image-based flow cytometry to classify granulocytes in terms of their phagocytosis and OB activities.7,9
Our research group has used various adaptations of this technique as an indicator of innate immune function in overweight, obese, and athletic populations for almost 20 years.10,11 The text below will provide the reader with step-by-step instructions for performing this assay and highlight areas that the reader may adapt to meet the needs of their research.
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NOTE: All blood collection procedures were conducted in accordance with the guidelines set forth by the Appalachian State University (ASU) Institutional Review Board (IRB).
1. Assay Preparation
2. Perform Assay
3. Flow Cytometry Acquisition
4. Data Analysis
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Prolonged and intensive exercise has profound effects on innate immune function, including natural killer cell function, macrophage cytokine-mediated response to viral infection, and granulocyte and monocyte phagocytosis and OB activity. Multiple studies indicate that granulocyte and monocyte phagocytosis increases significantly post-exercise, reflecting the inflammation induced by muscle damage and metabolic demands. In contrast, granulocyte and monocyte OB activity decreases post-exerci...
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This manuscript provides a step-by-step protocol for the determination of two indicators of granulocyte and monocyte function. We have identified a few steps that are critical to the success of this assay. One such step is the ice-bath incubation that occurs immediately prior to the addition of bacteria. Thorough cooling of all samples will minimize the effect of temperature on phagocytosis and OB activity. Another critical step is the addition of bacteria to each sample. A 8:1 bacteria:phagocyte ratio produces optimal r...
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The authors have nothing to disclose.
The authors would like to acknowledge Zack Shue, Casey John, and Lynn Cialdella-Kam for their assistance during the optimization of this procedure.
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| Name | Company | Catalog Number | Comments |
|---|---|---|---|
| 12 x 75 mm tubes, with cap | VWR | 20170-579 | You will need 2 tubes per sample ("H" and "F") plus 3 tubes per batch (for assay controls; "F", "H", and "Blood only"). |
| PBS (10x), pH 7.4 | Life Technologies | 70011-044 | |
| Bottle top 0.2 µm cellulose acetate filter (500 ml capacity) | Fisher Scientific | 09-741-07 | |
| Glucose, powder | Life Technologies | 15023-021 | |
| Citric acid (anhydrous, cell culture tested, plant cell culture tested) | Sigma-Aldrich | C2404-100G | |
| Sodium citrate tribasic dihydrate | Sigma-Aldrich | S4641-25G | |
| Dihydroethidium (Hydroethidine) (HE) | Life Technologies | D11347 | |
| Dimethyl sulfoxide (DMSO) Anhydrous | Life Technologies | D12345 | |
| Staphylococcus aureus (Wood strain without protein A) BioParticles, fluorescein conjugate (FITC) | Life Technologies | S2851 | |
| Staphylococcus aureus (Wood strain without protein A) BioParticles, unlabeled | Life Technologies | S-2859 | |
| Trypan Blue Solution, 0.4% | Life Technologies | 15250-061 | |
| 4.0 ml vacutainer containing 7.2 mg K2EDTA, spray-dried | VWR | BD367861 | You will need 1 K2EDTA blood collection tube per sample. |
| 4.0 ml vacutainer containing 68 USP units Lithium Heparin, spray-coated | VWR | BD367884 | You will need 1 Lithium Heparin blood collection tube per sample. |
| COULTER Ac·T 5diff CP | Beckman Coulter | 6605705 | i.e., hematology analyzer |
| COULTER Ac·T 5diff Rinse | Beckman Coulter | 8547167 | |
| COULTER Ac·T 5diff Fix | Beckman Coulter | 8547171 | |
| COULTER Ac·T 5diff WBC Lyse | Beckman Coulter | 8547170 | |
| COULTER Ac·T 5diff Hgb Lyse | Beckman Coulter | 8547168 | |
| COULTER Ac·T 5diff Cal Calibrator | Beckman Coulter | 7547175 | |
| COULTER Ac·T 5diff Control Plus | Beckman Coulter | 7547198 | |
| AcT 5diff Diluent | Beckman Coulter | 8547169 | |
| 200 µl extended-length pipette tips | VWR | 37001-526 | |
| Insulated ice pan | VWR | 89198-980 | For ice water bath. |
| Open metal tube rack | VWR | 60916-702 | |
| Fetal Bovine Serum | Life Technologies | 26140-111 | |
| TQ-Prep Workstation | Beckman Coulter | 6605429 | i.e., automated cell lyse preparation workstation |
| ImmunoPrep Reagent System | Beckman Coulter | 7546999 | i.e., RBC lyse/WBC fix reagent system |
| Cytomics FC500 MCL Flow Cytometry System with CXP Software | Beckman Coulter | 626553 | |
| IsoFlow Sheath Fluid | Beckman Coulter | 8547008 | |
| COULTER CLENZ | Beckman Coulter | 8546929 | |
| Flow-Check Fluorospheres | Beckman Coulter | 6605359 | i.e., alignment and fluidics verification fluorospheres |
| FlowJo Software | FlowJo | FlowJo | i.e., flow cytometry analysis software |
| Excel Software | Microsoft | Microsoft Excel | i.e., electronic spreadsheet program |
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