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Method Article
In this protocol, lymphocytes are placed in the top chamber of a transmigration system, separated from the bottom chamber by a porous membrane. Chemokine is added to the bottom chamber, which induces active migration along a chemokine gradient. After 48 h, lymphocytes are counted in both chambers to quantitate transmigration.
Herein, we present an efficient method that can be executed with basic laboratory skills and materials to assess lymphocyte chemokinetic movement in an ex vivo transmigration system. Group 2 innate lymphoid cells (ILC2) and CD4+ T helper cells were isolated from spleens and lungs of chicken egg ovalbumin (OVA)-challenged BALB/c mice. We confirmed the expression of CCR4 on both CD4+ T cells and ILC2, comparatively. CCL17 and CCL22 are the known ligands for CCR4; therefore, using this ex vivo transmigration method we examined CCL17- and CCL22-induced movement of CCR4+ lymphocytes. To establish chemokine gradients, CCL17 and CCL22 were placed in the bottom chamber of the transmigration system. Isolated lymphocytes were then added to top chambers and over a 48 h period the lymphocytes actively migrated through 3 µm pores towards the chemokine in the bottom chamber. This is an effective system for determining the chemokinetics of lymphocytes, but, understandably, does not mimic the complexities found in the in vivo organ microenvironments. This is one limitation of the method that can be overcome by the addition of in situ imaging of the organ and lymphocytes under study. In contrast, the advantage of this method is that is can be performed by an entry-level technician at a much more cost-effective rate than live imaging. As therapeutic compounds become available to enhance migration, as in the case of tumor infiltrating cytotoxic immune cells, or to inhibit migration, perhaps in the case of autoimmune diseases where immunopathology is of concern, this method can be used as a screening tool. In general, the method is effective if the chemokine of interest is consistently generating chemokinetics at a statistically higher level than the media control. In such cases, the degree of inhibition/enhancement by a given compound can be determined as well.
This original transmigration method was presented by Stephen Boyden in 1962 in the Journal of Experimental Medicine1. Much of what we know about chemotaxis and chemokinetics would not be possible without the development of the Boyden chamber. Prior to the discovery of the first chemokine in 1977, ex vivo transmigration systems were used to learn about serum-factors that could arrest cellular movement in macrophages while amplifying cellular motility in neutrophils1,2. A massive wealth of knowledge has been developed regarding immune cell migration, and to date, 47 chemokines have now been discovered with 19 corresponding receptors3,4. In addition, multitudes of inhibitors/enhancers of these chemokine pathways have undergone development for therapeutic purposes5,6,7,8. Many of those compounds have been tested in similar transmigration chambers to understand direct interactions between the compounds and immune cell responsiveness to a given chemokine9.
Transmigration, or diapedesis, into inflamed tissue is an essential process to a healthy inflammatory response to clear infection10,11. A Boyden chamber, transmigration system, or transwell apparatus are generally composed of two chambers separated by a porous membrane1,12. The bottom chamber most often holds media containing the chemokine of interest, while leukocytes are placed in the top chamber. The size of the pore in the membrane can be selected based on the size of the cell of interest. For this project, we selected a 3 µm porous membrane, as lymphoid cells are 7-20 µm in size, depending on the stage of cellular development. This pore size ensures that these cells are not passively falling through the pores, but that they are actively migrating in response to the chemokine gradient.
The major advantage of this protocol is its cost effectiveness. In vivo transmigration is difficult because it requires extensive training in animal handling and surgery, and often involves high-powered microscopy that is not always available to a researcher. Cost effective screening of compounds thought to enhance or inhibit transmigration can be accomplished in advance of in vivo imaging. Because the transmigration system is tightly controlled, cells may be treated initially then added to the transwell apparatus, or, vice versa, the chemokine may be treated first with a chemokine inhibitor then cells added to the transwell apparatus. Lastly, endothelial cells and/or basement membrane proteins can be added to the bottom of the transwell insert 1-2 days prior to the transmigration experiment to understand the involvement of these barrier cells in chemokinetics. Again, these manipulations of the system provide a powerful means of determining important information about the effectiveness of a given compound in advance of more complicated in vivo studies.
Utilizing a transmigration chamber system is an effective way to assess lymphocyte mobility under various in vivo and in vitro conditions12,13,14. Herein, we describe an optimized method for assessing ex vivo lymphocyte responsiveness to chemokines in a transmigration chamber. In this example experiment, CD4+ T cells and group 2 innate lymphoid cells (ILC2) were isolated from male and female, BALB/c mice following OVA-allergen exposure. A hypothesis was generated that CCR4+ CD45+ Lineage- (LIN-) ILC2 from allergen-challenged mice would migrate more efficiently towards CCL17 and CCL22 than CCR4+ CD4+ T helper cells. CCL17 and CCL22 are chemokines commonly produced by dendritic cells and macrophages of the M2 (allergic) phenotype, among other cells, in allergy15,16. CCL17 and CCL22 can be thought of as biomarkers of allergic inflammation as they are readily detected in the lungs during airway exacerbations16,17,18. Importantly, CCR4 expression is elevated in comparison to untreated controls, as revealed in bioinformatic data generated from ILC2 isolated from house dust mite treated animals, and similarly ILC2 from naïve animals treated ex vivo with IL-33 (allergen-promoting innate cytokine) upregulates CCR419,20. Furthermore, according to data for ILC2 in the Immunological Genome Project database (www.immgen.org), CCR4 mRNA is highly expressed in these innate immune cells. To date, little is known regarding trafficking of ILC2 into tissues, but it is likely that the ILC2 and CD4+ T cells use similar chemokines and receptors for chemotaxis and chemokinetics as they express similar transcription factors and receptors. Thus, we compared CCL17 versus CCL22 responsiveness, of ILC2 and CD4+ T lymphocytes, from both male and female, OVA-challenged animals.
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All methods described here were reviewed and approved by the Institutional Animal Care and Use Committees at the University of Nebraska Medical Center (UNMC) and the University of Utah.
1. Setup and Preparation of Reagents
2. Preparation of Allergen-challenged BALB/c Mice
NOTE: Male and female BALB/c mice were purchased from Charles River (UNMC) or Jackson Laboratories (University of Utah) at 6 to 8 weeks of age.
3. Isolation of CD4+ T Cells from Spleens and Lungs of OVA-challenged Mice
4. Determine CCR4 Expression on CD4+ T Cells and Group 2 Innate Lymphoid Cells (ILC2) from OVA-challenged Animals by Flow Cytometry
NOTE: The following steps may be performed on an open bench top as they are non-sterile techniques.
5. Ex Vivo Transmigration Procedure
NOTE: The following steps should be performed in a Biological Safety Cabinet, as they require sterile technique.
6. Quantification of Ex Vivo Transmigration
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CCR4 expression on CD4+ T cells and ILC2.
For the success of the ex vivo transmigration experiment, it is imperative to determine whether the lymphocytes are responsive to CCL17 and CCL22 through CCR4; therefore, we determined CCR4 expression on both CD4+ T cells and ILC2 by flow cytometry. While it is well known that OVA-specific CD4+ helper T cells express CCR4, less is known of the expression of CCR4 on ILC2. Figure 1 show...
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Herein, we present a well-established method for assessing chemokine-induced migration of lymphocytes in an ex vivo transmigration system. There are several critical steps in the protocol, the first of which is verifying the expression of the correct chemokine receptor on the immune cells in the experiment. In our hands, we chose CCR4 because of the body of literature that highlights the importance of CCR4 on Th2 helper T cells in allergic inflammation. Ovalbumin-induced inflammation was shown previously to be limited by...
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The authors have no financial disclosures or conflicts of interest to disclose.
This work was funded by the American Lung Association (K.J.W.), the Memorial Eugene Kenney fund awarded to T.A.W. and K.J.W., generous start-up support from the University of Utah for K.J.W., and a Department of Veterans Affairs award to T.A.W. (VA I01BX0003635). T.A.W. is the recipient of a Research Career Scientist Award (IK6 BX003781) from the Department of Veterans Affairs. The authors wish to acknowledge editorial assistance from Ms. Lisa Chudomelka. The authors thank the UNMC Flow Cytometry core for their support in collecting the flow cytometry data generated for this manuscript.
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Name | Company | Catalog Number | Comments |
0.4% Trypan Blue | Sigma-Aldrich | 15250061 | |
1 mL syringe | BD Bioscience | 329424 | U-100 Syringes Micro-Fine 28 G 1/2" 1cc |
100x Penicillin-Streptomycin, L-Glutamine | Gibco | 10378-016 | Dilute to 1x in RPMI media |
15 mL conical tubes | Olympus Plastics | 28-101 | polypropylene tubes |
3 μm transwell inserts | Genesee Scientific | 25-288 | 24-well plate containing 12 transwell inserts |
3x stabilizing fixative | BD Pharmigen | 338036 | Prepare 1x solution according to manufacturers protocol |
5 mL polystyrene tubes | STEM Cell Technologies | 38007 | |
50 mL conical tubes | Olympus Plastics | 28-106 | polypropylene tubes |
8-chamber easy separation magnet | STEM Cell Technologies | 18103 | |
ACK Lysing Buffer | Life Technologies Corporation | A1049201 | |
Advanced cell strainer, 40 μm | Genesee Scientific | 25-375 | nylon mesh, 40 μm strainers |
Aluminum Hydroxide, Reagent Grade | Sigma-Aldrich | 239186-25G | 20 mg/mL |
anti-mouse CCR4; APC-conjugated | Biolegend | 131211 | 0.5 μg/test |
anti-mouse CD11b | BD Pharmigen | 557396 | 0.5 μg/test |
anti-mouse CD11c; PE eFluor 610 | Thermo-Fischer Scientific | 61-0114-82 | 0.25 μg/test |
anti-mouse CD16/32, Fc block | BD Pharmigen | 553141 | 0.5 μg/test |
anti-mouse CD19; APC-eFluor 780 conjugated | Thermo-Fischer Scientific | 47-0193-82 | 0.5 μg/test |
anti-mouse CD3; PE Cy 7-conjugated | BD Pharmigen | 552774 | 0.25 μg/test |
anti-mouse CD45; PE conjugated | BD Pharmigen | 56087 | 0.5 μg/test |
anti-mouse ICOS (CD278) | BD Pharmigen | 564070 | 0.5 μg/test |
anti-mouse NK1.1 (CD161); FITC-conjugated | BD Pharmigen | 553164 | 0.25 μg/test |
anti-mouse ST2 (IL-33R); PerCP Cy5.5 conjugated | Biolegend | 145311 | 0.5 μg/test |
Automated Cell Counter | BIORAD | 1450102 | |
Automated Dissociator | MACS Miltenyi Biotec | 130-093-235 | |
Bovine Serum Albumin, Lyophilized Powder | Sigma-Aldrich | A2153-10G | 0.5% in serum-free RPMI |
Cell Counter Clides | BIORAD | 1450015 | |
Chicken Egg Ovalbumin, Grade V | Sigma-Aldrich | A5503-10G | 500 μg/mL |
Collagenase, Type 1, Filtered | Worthington Biochemical Corporation | CLSS-1, purchase as 5 X 50 mg vials (LS004216) | 25 U/mL in RPMI |
Compensation beads | Affymetrix | 01-1111-41 | 1 drop per contol tube |
Dissociation Tubes | MACS Miltenyi Biotec | 130-096-335 | |
FACS Buffer | BD Pharmigen | 554657 | 1x PBS + 2% FBS, w/ sodium azide; stored at 4 °C |
Heat Inactivated-FBS | Genesee Scientific | 25-525H | 10% in complete RPMI & ILC2 Expansion Media |
Mouse CCL17 | GenScript | Z02954-20 | 50 ng/mL |
Mouse CCL22 | GenScript | Z02856-20 | 50 ng/mL |
Mouse CD4+ T cell enrichment kit | STEM Cell Technologies | 19852 | |
Mouse IL-2 | GenScript | Z02764-20 | 20 ng/mL |
Mouse ILC2 enrichment kit | STEM Cell Technologies | 19842 | |
Mouse recombinant IL-33 | STEM Cell Technologies | 78044 | 20 ng/mL |
RPMI | Life Technologies Corporation | 22400071 | |
Separation Buffer | STEM Cell Technologies | 20144 | 1x PBS + 2% FBS; stored at 4 °C |
Small animal nebulizer and chamber | Data Sciences International | ||
Sterile saline | Baxter | 2F7124; NDC 0338-0048-04 | 0.9% Sodium Chloride |
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