time-lapse imaging to study activated murine cd8+ t-cell migration dynamics

Elucidating T-Cell Kinetics: Methods for Real-Time Migration Analysis

T cells are the major effectors of the adaptive, antigen-specific immune response. On a population level, T cells are heterogeneous, comprised of cellular subsets with distinct specialized functions. Importantly, CD8+ T cells are the main cytolytic effectors of the immune system, which directly eliminate infected or dysfunctional cells1.
Mature CD8+ T cells reside in tissue and circulate through blood and lymphatics in search of antigens. During infection, T cells are presented with antigens in blood or tissue and quickly drain to the spleen or nearest draining lymph node to begin a productive immune response. In either case, T cells become activated, undergo clonal expansion, and leave the lymphatic system to enter the blood, if not already there. During this process, intracellular signaling confers the downregulation of lymphatic homing receptors and the upregulation of numerous integrin and chemokine receptors essential for tissue-specific migration2. Ultimately, the directed migration of T cells to sites of infection is driven by converging environmental signals that include integrin and chemokine signaling.
Chemokines can be broadly categorized into two main classes: (1) homeostatic signals, which are essential for differentiation, survival, and basal function, and (2) inflammatory signals, such as CXCL9, CXCL10, and CCL3, which are required for chemotaxis. Generally, chemokines create a signal gradient that drives directional migration, known as chemotaxis, in addition to activating integrin expression1. Chemotaxis is finely regulated and highly sensitive, with T cells capable of responding to tiny changes in gradient that can lead them toward a specific direction or location.
In addition to these T cell-related factors, migration is also affected by the extracellular matrix (ECM) composition and density. The ECM is made up of a dense network of proteins, including collagen and proteoglycans, which provide the scaffold for adhesive integrin receptors on T cells. Integrins are a diverse family of transmembrane proteins, each with highly specialized binding domains and downstream signaling effects. Dynamic expression of integrin receptors on the surface of a T cell enables quick adaptation to their changing environments3. Importantly, integrins connect the ECM and intracellular cytoskeletal actin networks that work together to generate the propelling force required for T cell movement.
In summary, migration patterns vary based on the immune cell phenotype or environmental signals. These complex biological processes are tightly regulated by the expression of cytokines, chemokines, and integrins on the surface of the T cell, surrounding cells, and the local, infected tissue. In vivo, these migratory mechanisms can be&#160;complex and may result from several additive signals4. Due to this complexity, it can be impossible to establish a causal relationship between seemingly interlocked variables. To overcome this, there are several in vitro approaches to study specific aspects of T cell migration such as response to specific chemokine signals and the interaction between T cell integrins and ECM binding proteins. This protocol addresses methods to isolate and activate murine CD8+ T cells, with in vitro migration assays in two-dimensional space and computational analysis tools for analyzing specified T cell migration. These methods are advantageous to the user because they do not require sophisticated materials or devices, as with some other cell migration assays described in the literature. Cell migration data generated with these methods can&#160;provide evidence of immune responses in a simplistic manner that enables further, informed investigation in vivo.

Author Spotlight: Understanding Disease Mechanisms Through Real-Time Analysis of T-Cell Migration

Real-Time In Vitro Migration Assay for Primary Murine CD8+ T Cells

The goal of our research is to understand T cell migration patterns in highly defined environmental conditions to enable informed in vitro experimentation and decipher molecular interactions impacting migration. Live imaging, such as intravital multiphoton microscopy, is used for in vivo understanding of immune cell kinetics. But microfluidic devices are a common in vitro tool that offer precise control over the microenvironment that cannot be afforded in a live specimen.Our protocol allows us to analyze intricate signaling pathways and provides better understanding for targeted in vitro experiments to further address the biological roles of individual signals in a cell type specific manner. Our method is simple, reproducible and easy to access in research labs that have a brightfield microscope featuring an attached digital camera. Therefore, our approach ensures a reliable set of methods to study dynamic cell migration events.Our lab will focus on investigating the migration of immune cells, including T cells and neutrophils in a variety of disease settings, such as tumors and infection, thereby comprehending the mechanisms that are important to regulate immune cell migration. This will help in developing the therapeutic methods to help treat and prevent disease.

Time-Lapse Imaging to Study Activated Murine CD8+ T-Cell Migration Dynamics

time-lapse-imaging-to-study-activated-murine-cd8-t-cell-migration

Research

JoVE Journal

Immunology and Infection

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