The authors gratefully acknowledge funding by the DFG Collaborative Research Centers SFB 1181 and TRR 241. The Optical Imaging Centre Erlangen (OICE) and in particular Ralf Palmisano, Philipp Tripal and Tina Fraa&#223; (Project Z2 of the DFG CRC 1181) are acknowledged for expert technical support for light-sheet fluorescence microscopic imaging.

M.F. Neurath has served as an advisor for Pentax, Giuliani, MSD, Abbvie, Janssen, Takeda and Boehringer. The remaining authors do not disclose any conflict.

The here described experimental setting provides the opportunity to monitor the lung homing capacity of primary human immune cells under in vivo inflammatory conditions and thereby relevantly complements classically performed in vitro adhesion and chemotaxis assays. To take into account specific anatomic organ characteristics of the lung, important aspects of immune cell homing (including chemotaxis and cell distribution within the target organ) as well as the clinical relevance and transfera...

Classic inflammatory disorders of the lung, such as allergic asthma and chronic obstructive pulmonary disease (COPD), are well known to be driven by an increased recruitment of activated lymphocytes into the pulmonary tissue1,2. Lymphocyte-released cytokines (e.g., IL-4, IL-5, IL-9, IL-13, IFN-&#947; and TNF-&#945;) further promote chemotaxis of innate and adaptive immune cells, induce fibrotic airway remodeling or directly damage the lung parenchyma2. So far, the underlying mechanisms responsible for the pathological accumulation of lymphocytes within lung tissue are not yet fully understood. In analogy to tissue-selective T cell imprinting described for gut and skin homing, pulmonary dendritic cells (DCs) are obviously able to prime peripheral T cells for preferential lung infiltration, at least partly via the induction of CCR4 expression on the surface of lymphocytes3. Besides CCR4, airway-infiltrating T cells are also characterized by a particularly increased expression of the chemokine receptors CCR5 and CXCR3 compared to T cells within the peripheral blood1,4,5. Overall, existing data are consistent with the concept that lung homing of T lymphocytes under physiological or inflammatory conditions involves a number of different chemokine receptors and their respective ligands and thus crucially depends on a closely controlled collaboration between innate and adaptive immune cells1. Especially, during the initial phase of pathogen or allergen exposure, cells of the innate immune system respond to TLR stimulation or to IgE-mediated cross-linking by the immediate release of different chemoattractants, like LTB4, CCL1, CCL17, CCL22, CCL20, CXCL10 and PGD21,6,7. As a prime example, the interaction between PGD2 and the chemoattractant receptor CRTh2 is known to be of particular importance for chemotaxis of Th2 cells and thus appeared as promising therapeutic target in the clinical management of asthma. Indeed, patients with moderate asthma showed an improvement of symptoms and a significant increase of the forced expiratory volume in one second (FEV1) after treatment with a selective CRTh2 antagonist compared to the placebo group8,9. In a more progressed state of the inflammatory response, already recruited T cells are able to further amplify pulmonary lymphocyte accumulation via the release of IL-4 and IL-13 as potent stimuli for pulmonary DCs. Subsequently, these myeloid-derived innate cells up-regulate the expression of CCL17 and CCL22 in a STAT6-dependent manner1,10,11.&#160; Although the complexity of the described scenario still hinders a complete understanding of T cell lung homing, it offers a plethora of molecular targets for a potentially optimized therapeutic control of inflammatory or allergic pulmonary diseases. Therefore, there is an urgent need of innovative experimental techniques, which are able to further deepen and complement our knowledge in the field of T cell chemotaxis and lung homing.
Due to the fact that lung homing of lymphocytes within the human body is influenced by multiple cellular, humoral and physical parameters1, most of the existing experimental methods are not able to model the whole complexity of this immunological process. Instead, many standard protocols for the analysis of lung homing selectively focus on a specific aspect involved in the cascade of lymphocyte attraction, adhesion, migration and retention. Besides a purely descriptive determination of the mRNA or protein expression pattern of integrins and chemokine receptors on peripheral or lung-infiltrating lymphocytes and the complementary measurement of respective chemokine levels in blood, bronchoalveolar lavage (BAL) or pulmonary tissue12,13,14,15, well-established in vitro cell culture assays allow a functional characterization of lymphocyte adhesion or chemotaxis upon defined experimental conditions16,17,18. In principle, static in vitro adhesion assays monitor the binding capacity of cultured lymphocytes to an endothelial monolayer or to glass slides coated with recombinant endothelial adhesion molecules (e.g., MAdCAM-1, VCAM-1), while standard in vitro chemotaxis assays are usually applied in order to quantify the ability of lymphocytes to migrate along a chemokine gradient in a transwell system19. Both in vitro settings enable a controlled adjustment and modulation of experimental conditions, but on the other hand lack important variables known to critically impact on in vivo chemotaxis and adhesion of lymphocytes. Predominantly, static cell culture assays disregard the influence of shear forces caused by the permanent blood flow19 and potentially neglect the involvement of the surrounding immunological milieu and interacting non-lymphocyte immune cells, both present in a living organism. In order to overcome these limitations, the interpretation of results acquired in static in vitro chemotaxis or adherence assays need further validation in dynamic adhesion experiments under flow conditions20,21 and in in vivo models of inflammatory organ pathology19. Indeed, important conclusions on the regulation of T cell lung homing under inflammatory or allergic conditions could be drawn from animal studies analyzing genetically modified mice in defined models of different pulmonary diseases3,22,23. The quantitative comparison of lung infiltrating lymphocytes between wildtype mice and mice with a deficiency for a specific gene of interest represents a well-established and broadly used tool for defining the impact of particular cellular pathways or receptors on the disease-driven pattern of T cell distribution. However, in contrast to before discussed in vitro cell culture assays, a study design based on classical animal models lacks the ability to analyze and monitor primary human T cells directly derived from the blood or BAL of patients suffering from an inflammatory lung disease. Thus, it still remains challenging to functionally validate whether a diagnostically specified lung disease is able to imprint human lymphocytes for preferential lung tropism and how far clinical parameters might impact on this scenario. Recently, a very elegant in vivo approach was introduced in the context of inflammatory bowel diseases (IBD), which was able to overcome most of these limitations and opened new avenues for advanced translational studies on intestinal lymphocyte homing24. Taking advantage of protocols for solvent-based tissue clearing followed by cross-sectional light-sheet fluorescence microscopy as a powerful imaging tool, it was possible to visualize the infiltration and distribution of adoptively transferred human T cells in the intestine of colitic immunodeficient mice24. In particular, this experimental setting implemented two main innovations: (1) Primary human immune cells can be analyzed under experimentally defined in vivo conditions; (2) a rather large area of the diseased organ (about 1.5&#160;cm&#160;x&#160;1.5&#160;cm) can be imaged in high resolution quality, followed by 3D-reconstruction. Moreover, several recent studies successfully established the use of solvent-based tissue clearing and light-sheet fluorescence microscopy as important tools for advanced lung imaging25,26. In order to benefit from this technological progress in the field of pulmonary immunology, we now adopted the system for analysis of lung homing.
The here presented protocol provides a step-by-step introduction how to purify and fluorescently label primary human T cells for transfer into mice with induced pulmonary inflammation and, moreover, describes in detail the subsequent process of light-sheet fluorescence microscopic imaging, including organ preparation and image processing. Overall, we hope to support future translational studies in the field of inflammatory or allergic lung diseases by introducing a sophisticated, but nevertheless feasible, experimental model for monitoring human lymphocyte lung homing upon in vivo conditions.

<table><tbody><tr><td>Agarose NEEO Ultra</td><td>Carl Roth GmbH + Co. KG, Karlsruhe, Germany</td><td>2267.4</td><td></td></tr><tr><td>AlexaFlour594 anti-human CD45 antibody</td><td>BioLegend, San Diego, USA</td><td>304060</td><td></td></tr><tr><td>Ammonium chloride</td><td>Carl Roth GmbH + Co. KG, Karlsruhe, Germany</td><td>K2981</td><td></td></tr><tr><td>Cannula 21 G</td><td>Becton, Dickinson and Company, Franklin Lakes, USA</td><td>301300</td><td></td></tr><tr><td>Cell proliferation dye eflour670</td><td>eBioscience Inc., San Diego, USA</td><td>65-0840-85</td><td></td></tr><tr><td>CD4 MicroBeads, human</td><td>Miltenyi Biotech GmbH, Bergisch-Gladbach, Germany</td><td>130-045-101</td><td></td></tr><tr><td>EDTA (ethylenediaminetetraacetic acid)</td><td>Carl Roth GmbH + Co. KG, Karlsruhe, Germany</td><td>8043.1</td><td></td></tr><tr><td>Potassium-EDTA blood collection tube, 9 mL</td><td>Sarstedt AG &amp;amp; Co., N&amp;uuml;mbrecht, Germany</td><td>21066001</td><td></td></tr><tr><td>Ethly cinnamate (ECi)</td><td>Sigma-Aldrich, Steinheim, Germany</td><td>112372-100G</td><td></td></tr><tr><td>Ethanol &amp;ge; 99.5% (EtOH)</td><td>Carl Roth GmbH + Co. KG, Karlsruhe, Germany</td><td>5054.3</td><td></td></tr><tr><td>FBS (fetal bovine serum) Good Forte</td><td>PAN-Biotech GmbH, Aidenbach, Germany</td><td>P40-47500</td><td></td></tr><tr><td>Filter 100 &amp;micro;m&amp;nbsp;</td><td>VWR International Germany GmbH, Darmstadt, Germany</td><td>732-2758</td><td></td></tr><tr><td>Imaris Image Analysis Software 9.0.2</td><td>Bitplane AG, Zurich, Switzerland</td><td>n.a.</td><td></td></tr><tr><td>ImspectorPro software</td><td>Abberior Instruments GmbH, G&amp;ouml;ttingen, Germany</td><td>n.a.</td><td></td></tr><tr><td>Ketamin&amp;nbsp;</td><td>Inresa Arzneimittel GmbH, Freiburg, Germany</td><td>3617KET-V</td><td></td></tr><tr><td>LaVision UltraMicroscope II</td><td>LaVision BioTec GmbH, Bielefeld, Germany</td><td>n.a.</td><td></td></tr><tr><td>MACS MultiStand</td><td>Miltenyi Biotech GmbH, Bergisch-Gladbach, Germany</td><td>130-042-303</td><td></td></tr><tr><td>Multifly cannula 20 G</td><td>Sarstedt AG &amp;amp; Co., N&amp;uuml;mbrecht, Germany</td><td>851638035</td><td></td></tr><tr><td>30 G needle</td><td>B. Braun Melsungen AG, Melsungen, Hessen, Germany</td><td>9161502</td><td></td></tr><tr><td>Neubauer counting chamber</td><td>neoLab Migge GmbH, Heidelberg, Germany</td><td>C-1003</td><td></td></tr><tr><td>Pattex Glue</td><td>Henkel AG &amp;amp; Co, D&amp;uuml;sseldorf, Germany</td><td>PSK1C</td><td></td></tr><tr><td>LS column</td><td>Miltenyi Biotech GmbH, Bergisch-Gladbach, Germany</td><td>130-042-401</td><td></td></tr><tr><td>Lymphocyte Separation Media (Density 1,077 g/mL)</td><td>anprotec</td><td>AC-AF-0018</td><td></td></tr><tr><td>Papain</td><td>Merck</td><td>1,071,440,025</td><td></td></tr><tr><td>PBS Dulbecco (phosphate buffered saline)</td><td>Biochrom GmbH, Berlin, Germany</td><td>L182-10</td><td></td></tr><tr><td>PerCP/Cy5.5 anti-human CD4</td><td>BioLegend, San Diego, USA</td><td>317428</td><td></td></tr><tr><td>PerCP/Cy5.5 mouse IgG2b, &amp;kappa; isotype Ctrl</td><td>BioLegend, San Diego, USA</td><td>400337</td><td></td></tr><tr><td>PFA (paraformaldehyde)</td><td>Carl Roth GmbH + Co. KG, Karlsruhe, Germany</td><td>0335.1</td><td></td></tr><tr><td>Potassium hydrogen carbonate</td><td>Carl Roth GmbH + Co. KG, Karlsruhe, Germany</td><td>P7481</td><td></td></tr><tr><td>Serological pipette 10 mL</td><td>Sarstedt AG &amp;amp; Co., N&amp;uuml;mbrecht, Germany</td><td>86.1254.001&amp;nbsp;</td><td></td></tr><tr><td>Syringe 1 mL</td><td>B. Braun Melsungen AG, Melsungen, Hessen, Germany</td><td>9166017V</td><td></td></tr><tr><td>Syringe 5 mL</td><td>Becton, Dickinson and Company, Franklin Lakes, USA</td><td>260067</td><td></td></tr><tr><td>Syringe 20 mL</td><td>Becton, Dickinson and Company, Franklin Lakes, USA</td><td>260069</td><td></td></tr><tr><td>Tube 1.5 mL</td><td>Sarstedt AG &amp;amp; Co., N&amp;uuml;mbrecht, Germany</td><td>72,706,400</td><td></td></tr><tr><td>Tube 2 mL</td><td>Sarstedt AG &amp;amp; Co., N&amp;uuml;mbrecht, Germany</td><td>72.695.400&amp;nbsp;</td><td></td></tr><tr><td>Tube 2 mL, brown</td><td>Sarstedt AG &amp;amp; Co., N&amp;uuml;mbrecht, Germany</td><td>72,695,001</td><td></td></tr><tr><td>Tube 15 mL</td><td>Sarstedt AG &amp;amp; Co., N&amp;uuml;mbrecht, Germany</td><td>62.554.502&amp;nbsp;</td><td></td></tr><tr><td>Tube 50 mL</td><td>Sarstedt AG &amp;amp; Co., N&amp;uuml;mbrecht, Germany</td><td>62.547.254&amp;nbsp;</td><td></td></tr><tr><td>QuadroMACS Separator</td><td>Miltenyi Biotech GmbH, Bergisch-Gladbach, Germany</td><td>130-090-976</td><td></td></tr><tr><td>Xylazin (Rompun 2%)</td><td>Bayer Vital GmbH, Leverkusen, Germany</td><td>KPOBD32</td><td></td></tr></tbody></table>

advanced imaging of lung homing human lymphocytes in an experimental in vivo model of allergic inflammation based on light-sheet microscopy

Overwhelming tissue accumulation of highly activated immune cells represents a hallmark of various chronic inflammatory diseases and emerged as an attractive therapeutic target in the clinical management of affected patients. In order to further optimize strategies aiming at therapeutic regulation of pathologically imbalanced tissue infiltration of pro-inflammatory immune cells, it will be of particular importance to achieve improved insights into disease- and organ-specific homing properties of peripheral lymphocytes. The here described experimental protocol allows to monitor lung accumulation of fluorescently labeled and adoptively transferred human lymphocytes in the context of papain-induced pulmonary inflammation. In contrast to standard in vitro assays frequently used for the analysis of immune cell migration and chemotaxis, the now introduced in vivo setting takes into account lung-specific aspects of tissue organization and the influence of the complex inflammatory scenario taking place in the living murine organism. Moreover, three-dimensional cross-sectional light-sheet fluorescence microscopic imaging does not only provide quantitative data on infiltrating immune cells, but also depicts the pattern of immune cell localization within the inflamed lung. Overall, we are able to introduce an innovative technique of high value for immunological research in the field of chronic inflammatory lung diseases, which can be easily applied by following the provided step-by-step protocol.

The presented protocol describes an experimental mouse model, which allows monitoring and quantifying the accumulation of adoptively transferred human T lymphocytes in the lung via light-sheet fluorescence microscopy.&#160;Figure 1A provides a schematic overview of the in vivo steps of the experimental schedule. In order to guarantee reliable results, it is of substantial importance to ensure a good quality of the isolated and fluorescently labeled human CD4+ T ce...

Watch this Scientific Journal Video about Advanced Imaging of Lung Homing Human Lymphocytes in an Experimental In Vivo Model of Allergic Inflammation Based on Light-sheet Microscopy at JoVE.com

Advanced Imaging of Lung Homing Human Lymphocytes in an Experimental In Vivo Model of Allergic Inflammation Based on Light-sheet Microscopy

The here introduced protocol allows characterization of the lung homing capacity of primary human lymphocytes under in vivo inflammatory conditions. Pulmonary infiltration of adoptively transferred human immune cells in a mouse model of allergic inflammation can be imaged and quantified by light-sheet fluorescence microscopy of chemically cleared lung tissue.

Overwhelming tissue accumulation of highly activated immune cells represents a hallmark of various chronic inflammatory diseases and emerged as an ...

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Research

JoVE Journal

Medicine

7.6K Views.  University Hospital of Erlangen. Onze techniek maakt het mogelijk om de nauwkeurige beeldvorming van longgeaccumuleerde menselijke immuuncellen in in vivo ontstekingsaandoeningen te geven die opwindende inzichten geven in het proces van T-cellonghoing. Dit protocol ondersteunt translationeel onderzoek naar T-cellongen en kan daardoor helpen bij de identificatie van nieuwe doelen voor een geoptimaliseerde therapie van ontstekings- of allergische longziekten. In het bijzonder, de mogelijkheid om de invloed van ziekte-specifiek...

Video: Advanced Imaging of Lung Homing Human Lymphocytes in an Experimental In Vivo Model of Allergic Inflammation Based on Light-sheet Microscopy

Non-invasive Imaging of Leukocyte Homing and Migration in vivo

Two-photon (2P) microscopy is a high resolution imaging technique that has been broadly adapted by biologists. The value of 2P microscopy is that it provides rich spatiotemporal information regarding cell behaviors within intact tissues and in live mice. Leukocyte recruitment plays a significant role in host defense against infection and when unchecked, can contribute to inflammatory and autoimmune diseases. Studying leukocyte recruitment in vivo is technically challenging since cells are moving rapidly within vessels located deep within light scattering tissues. To date, most intravital imaging studies require surgical preparation to expose the blood vessels and tissues. To avoid the tissue damage and inflammation induced by surgery itself, here, we describe a non-invasive single-cell imaging approach that can be used to study leukocyte trafficking in the mouse footpad and phalanges. We discuss the technical aspects of our 2P imaging preparation and walk the reader through a typical experiment from initial set up to execution and data collection.

Non-invasive Imaging of Leukocyte Homing and Migration in vivo

Here, we describe a non-invasive two-photon (2P) microscopy approach to study leukocyte homing in the mouse footpad. We discuss the technical aspects of our tissue imaging preparation and walk the reader through a typical experiment from initial set up to execution and data collection.

Two-photon (2P) microscopy is a high resolution imaging technique that has been broadly adapted by biologists.  The value of 2P microscopy is that it ...

Immunology and Infection

Ex Vivo Imaging of Resident CD8 T Lymphocytes in Human Lung Tumor Slices Using Confocal Microscopy

CD8 T cell are key players in the fight against cancer. In order for CD8 T cells to kill tumor cells they need to enter into the tumor, migrate within the tumor microenvironment and respond adequately to tumor antigens. The recent development of improved imaging approaches, such as 2-photon microscopy, and the use of powerful mouse tumor models have shed light on some of the mechanisms that regulate anti-tumor T cell activities. Whereas such systems have provided valuable insights, they do not always predict human responses. In human, our knowledge in the field mainly comes from a description of fixed tumor samples from human patients, as well as in vitro studies. However, in vitro models lack the complex three-dimensional tumor milieu and, therefore, are incomplete approximations of in vivo T cell activities. Fresh slices made from explanted tissue represent a complex multi-cellular tumor environment that can act as an important link between co-cultured studies and animal models. Originally set up in murine lymph nodes1 and previously described in a JoVE article2, this approach has now been transposed to human tumors to examine the dynamics of both plated3&#160;as well as resident&#160;T cells4.
Here, a protocol for the preparation of human lung tumor slices, immunostaining of resident CD8 T and tumor cells, and tracking of CD8 T lymphocytes within the tumor microenvironment using confocal microscopy is described. This system is uniquely placed to screen for novel immunotherapy agents favoring T cell migration in tumors.

Ex Vivo Imaging of Resident CD8 T Lymphocytes in Human Lung Tumor Slices Using Confocal Microscopy

This protocol describes a method to image resident tumor-infiltrating CD8 T cells labeled with fluorescently coupled antibodies within human lung tumor slices. This technique permits real-time analyses of CD8 T cell migration using confocal microscopy.

CD8 T cell are key players in the fight against cancer. In order for CD8 T cells to kill tumor cells they need to enter into the tumor, migrate within the ...

Cancer Research

Dissection and 2-Photon Imaging of Peripheral Lymph Nodes in Mice

Two-photon imaging has revealed an elegant choreography of motility and cellular interactions within the lymph node under basal conditions and at the initiation of an immune response 1. Here, we present methods for adoptive transfer of labeled T cells, isolation of lymph nodes, and imaging motility of CD4+ T cells in the explanted lymph node as first described in 2002 2. Two-photon imaging of immune cells requires that the cells are fluorescently labeled, either by staining with a cell tracker dye or by expressing a fluorescent protein. We demonstrate the adoptive transfer procedure of injecting cells derived from donor mice into the tail vein of a recipient animal, where they home to lymphoid organs within approximately 15-30 min. We illustrate the isolation of a lymph node and describe methods to ensure proper mounting of the excised lymph node. Other considerations such as proper oxygenation of perfused media, temperature, and laser power are discussed. Finally, we present 3D video images of naive CD4+ T cells exhibiting steady state motility at 37&deg;C.

Two-photon imaging has uncovered lymphocyte motility and cellular interactions within the lymph node under basal conditions and durring an immune response 1. Here, we demonstrate adoptive transfer of T cells, isolation of lymph nodes, and imaging motility of CD4+ T cells in the explanted lymph node.

Two-photon imaging has revealed an elegant choreography of motility and cellular interactions within the lymph node under basal conditions and at the ...

Biology

Intravital Imaging of the Mouse Popliteal Lymph Node

Lymph nodes (LNs) are secondary lymphoid organs, which are strategically located throughout the body to allow for trapping and presentation of foreign antigens from peripheral tissues to prime the adaptive immune response. Juxtaposed between innate and adaptive immune responses, the LN is an ideal site to study immune cell interactions1,2. Lymphocytes (T cells, B cells and NK cells), dendritic cells (DCs), and macrophages comprise the bulk of bone marrow-derived cellular elements of the LN. These cells are strategically positioned in the LN to allow efficient surveillance of self antigens and potential foreign antigens3-5. The process by which lymphocytes successfully encounter cognate antigens is a subject of intense investigation in recent years, and involves an integration of molecular contacts including antigen receptors, adhesion molecules, chemokines, and stromal structures such as the fibro-reticular network2,6-12. 
Prior to the development of high-resolution real-time fluorescent in vivo imaging, investigators relied on static imaging, which only offers answers regarding morphology, position, and architecture. While these questions are fundamental in our understanding of immune cell behavior, the limitations intrinsic with this technique does not permit analysis to decipher lymphocyte trafficking and environmental clues that affect dynamic cell behavior. Recently, the development of intravital two-photon laser scanning microscopy (2P-LSM) has allowed investigators to view the dynamic movements and interactions of individual cells within live LNs in situ12-16. In particular, we and others have applied this technique to image cellular behavior and interactions within the popliteal LN, where its compact, dense nature offers the advantage of multiplex data acquisition over a large tissue area with diverse tissue sub-structures11,17-18. It is important to note that this technique offers added benefits over explanted tissue imaging techniques, which require disruption of blood, lymph flow, and ultimately the cellular dynamics of the system. Additionally, explanted tissues have a very limited window of time in which the tissue remains viable for imaging after explant. With proper hydration and monitoring of the animal's environmental conditions, the imaging time can be significantly extended with this intravital technique. Here, we present a detailed method of preparing mouse popliteal LN for the purpose of performing intravital imaging.

Recent advances in 2-photon microscopy have enabled real-time in situ imaging of live tissues in animal models, thereby enhancing our ability to investigate cellular behavior in both physiologic and pathologic conditions. Here, we outline the preparations required to perform intravital imaging of the mouse popliteal lymph node.

Lymph nodes (LNs) are secondary lymphoid organs, which are strategically located throughout the body to allow for trapping and presentation of foreign ...

Highly Resolved Intravital Striped-illumination Microscopy of Germinal Centers

Monitoring cellular communication by intravital deep-tissue multi-photon microscopy is the key for understanding the fate of immune cells within thick tissue samples and organs in health and disease. By controlling the scanning pattern in multi-photon microscopy and applying appropriate numerical algorithms, we developed a striped-illumination approach, which enabled us to achieve 3-fold better axial resolution and improved signal-to-noise ratio, i.e. contrast, in more than 100 &#181;m tissue depth within highly scattering tissue of lymphoid organs as compared to standard multi-photon microscopy. The acquisition speed as well as photobleaching and photodamage effects were similar to standard photo-multiplier-based technique, whereas the imaging depth was slightly lower due to the use of field detectors. By using the striped-illumination approach, we are able to observe the dynamics of immune complex deposits on secondary follicular dendritic cells &#8211; on the level of a few protein molecules in germinal centers.

High-resolution intravital imaging with enhanced contrast up to 120 &#181;m depth in lymph nodes of adult mice is achieved by spatially modulating the excitation pattern of a multi-focal two-photon microscope. In 100 &#181;m depth we measured resolutions of 487 nm (lateral) and 551 nm (axial), thus circumventing scattering and diffraction limits.

Monitoring cellular communication by intravital deep-tissue multi-photon microscopy is the key for understanding the fate of immune cells within thick ...

Precision-cut Mouse Lung Slices to Visualize Live Pulmonary Dendritic Cells

Inhalation of allergens and pathogens elicits multiple changes in a variety of immune cell types in the lung. Flow cytometry is a powerful technique for quantitative analysis of cell surface proteins on immune cells, but it provides no information on the localization and migration patterns of these cells within the lung. Similarly,&#160;chemotaxis assays can be performed to study the potential of cells to respond to chemotactic factors in vitro, but these assays do not reproduce the complex environment of the intact lung. In contrast to these aforementioned techniques, the location of individual cell types within the lung can be readily visualized by generating Precision-cut Lung Slices (PCLS), staining them with commercially available, fluorescently tagged antibodies, and visualizing the sections by confocal microscopy. PCLS can be used for both live and fixed lung tissue, and the slices can encompass areas as large as a cross section of an entire lobe. We have used this protocol to successfully visualize the location of a wide variety of cell types in the lung, including distinct types of dendritic cells, macrophages, neutrophils, T cells and B cells, as well as structural cells such as lymphatic, endothelial, and epithelial cells. The ability to visualize cellular interactions, such as those between dendritic cells and T cells, in live, three-dimensional lung tissue, can reveal how cells move within the lung and interact with one another at steady state and during inflammation. Thus, when used in combination with other procedures, such as flow cytometry and quantitative PCR, PCLS can contribute to a comprehensive understanding of cellular events that underlie allergic and inflammatory diseases of the lung.

We describe a method for generating Precision-cut Lung Slices (PCLS) and immunostaining them to visualize the localization of various immune cell types in the lung. Our protocol can be extended to visualize the location and function of many different cell types under a variety of conditions.

Inhalation of allergens and pathogens elicits multiple changes in a variety of immune cell types in the lung. Flow cytometry is a powerful technique for ...

Light-sheet Microscopy for Three-dimensional Visualization of Human Immune Cells

In vivo, activation, proliferation, and function of immune cells all occur in a three-dimensional (3D) environment, for instance in lymph nodes or tissues. Up to date, most in vitro systems rely on two-dimensional (2D) surfaces, such as cell-culture plates or coverslips. To optimally mimic physiological conditions in vitro, we utilize a simple 3D collagen matrix. Collagen is one of the major components of extracellular matrix (ECM) and has been widely used to constitute 3D matrices. For 3D imaging, the recently developed light-sheet microscopy technology (also referred to as single plane illumination microscopy) is featured with high acquisition speed, large penetration depth, low bleaching, and photocytotoxicity. Furthermore, light-sheet microscopy is particularly advantageous for long-term measurement. Here we describe an optimized protocol how to set up and handle human immune cells, e.g. primary human cytotoxic T lymphocytes (CTL) and natural killer (NK) cells in the 3D collagen matrix for usage with the light-sheet microscopy for live cell imaging and fixed samples. The procedure for image acquisition and analysis of cell migration are presented. A particular focus is given to highlight critical steps and factors for sample preparation and data analysis. This protocol can be employed for other types of suspension cells in a 3D collagen matrix and is not limited to immune cells.

Here, we present a protocol to visualize immune cells embedded in a three-dimensional (3D) collagen matrix using light-sheet microscopy. This protocol also elaborates how to track cell migration in 3D. This protocol can be employed for other types of suspension cells in the 3D matrix.

In vivo, activation, proliferation, and function of immune cells all occur in a three-dimensional (3D) environment, for instance in lymph nodes or ...

Quantitative Visualization of Leukocyte Infiltrate in a Murine Model of Fulminant Myocarditis by Light Sheet Microscopy

Light-sheet fluorescence microscopy (LSFM), in combination with chemical clearing protocols, has become the gold standard for analyzing fluorescently labelled structures in large biological specimens, and is down to cellular resolution. Meanwhile, the constant refinement of underlying protocols and the enhanced availability of specialized commercial systems enable us to investigate the microstructure of whole mouse organs and even allow for the characterization of cellular behavior in various live-cell imaging approaches. Here, we describe a protocol for the spatial whole-mount visualization and quantification of the CD45+ leukocyte population in inflamed mouse hearts. The method employs a transgenic mouse strain (CD11c.DTR)that has recently been shown to serve as a robust, inducible model for the study of the development of fulminant fatal myocarditis, characterized by lethal cardiac arrhythmias. This protocol includes myocarditis induction, intravital antibody-mediated cell staining, organ preparation, and LSFM with subsequent computer-assisted image post-processing. Although presented as a highly-adapted method for our particular scientific question, the protocol represents the blueprint of an easily adjustable system that can also target completely different fluorescent structures in other organs and even in other species.

Here, we describe a light-sheet microscopy approach to visualize the cardiac CD45+ leukocyte infiltrate in a murine model of aseptic fulminant myocarditis, which is induced by the intratracheal diphtheria toxin treatment of CD11c.DTR mice.

Light-sheet fluorescence microscopy (LSFM), in combination with chemical clearing protocols, has become the gold standard for analyzing fluorescently ...

Intravital Widefield Fluorescence Microscopy of Pulmonary Microcirculation in Experimental Acute Lung Injury Using a Vacuum-Stabilized Imaging System

Intravital imaging of leukocyte-endothelial interactions offers valuable insights into immune-mediated disease in live animals. The study of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) and other respiratory pathologies in vivo is difficult due to the limited accessibility and inherent motion artifacts of the lungs. Nonetheless, various approaches have been developed to overcome these challenges. This protocol describes a method for intravital fluorescence microscopy to study real-time leukocyte-endothelial interactions in the pulmonary microcirculation in an experimental model of ALI. An in vivo lung imaging system and 3-D printed intravital microscopy platform are used to secure the anesthetized mouse and stabilize the lung while minimizing confounding lung injury. Following preparation, widefield fluorescence microscopy is used to study leukocyte adhesion, leukocyte rolling, and capillary function. While the protocol presented here focuses on imaging in an acute model of inflammatory lung disease, it may also be adapted to study other pathological and physiological processes in the lung.

Intravital fluorescence microscopy can be utilized to study leukocyte-endothelial interactions and capillary perfusion in real-time. This protocol describes methods to image and quantify these parameters in the pulmonary microcirculation using a vacuum-stabilized lung imaging system.

Intravital imaging of leukocyte-endothelial interactions offers valuable insights into immune-mediated disease in live animals. The study of acute lung ...

Light-Sheet Microscopy and Tissue Clearing for Comprehensive Cardiac Imaging

Light-Sheet Imaging to Reveal Cardiac Structure in Rodent Hearts

Light-sheet microscopy (LSM) plays a pivotal role in comprehending the intricate three-dimensional (3D) structure of the heart, providing crucial insights into fundamental cardiac physiology and pathologic responses. We hereby delve into the development and implementation of the LSM technique to elucidate the micro-architecture of the heart in mouse models. The methodology integrates a customized LSM system with tissue clearing techniques, mitigating light scattering within cardiac tissues for volumetric imaging. The combination of conventional LSM with image stitching and multiview deconvolution approaches allows for the capture of the entire heart. To address the inherent trade-off between axial resolution and field of view (FOV), we further introduce an axially swept light-sheet microscopy (ASLM) method to minimize out-of-focus light and uniformly illuminate the heart across the propagation direction. In the meanwhile, tissue clearing methods such as iDISCO enhance light penetration, facilitating the visualization of deep structures and ensuring a comprehensive examination of the myocardium throughout the entire heart. The combination of the proposed LSM and tissue clearing methods presents a promising platform for researchers in resolving cardiac structures in rodent hearts, holding great potential for the understanding of cardiac morphogenesis and remodeling.

Author Spotlight: Customized Light-Sheet Imaging for Investigating Myocardial Structures in Rodent Hearts

The protocol utilizes advanced light-sheet microscopy along with adapted tissue clearing methods to investigate intricate cardiac structures in rodent hearts, holding great potential for the understanding of cardiac morphogenesis and remodeling.

Light-sheet microscopy (LSM) plays a pivotal role in comprehending the intricate three-dimensional (3D) structure of the heart, providing crucial insights ...

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