Chemokines control naive CD8(+) T cell selection of optimal lymph node antigen presenting cells

Cell Biology and Viral Immunology Sections, Laboratory of Viral Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
Journal of Experimental Medicine (Impact Factor: 13.91). 11/2011; 208(12):2511-24. DOI: 10.1084/jem.20102545
Source: PubMed

ABSTRACT Naive antiviral CD8(+) T cells are activated in the draining LN (DLN) by dendritic cells (DCs) presenting viral antigens. However, many viruses infect LN macrophages, which participate in initiation of innate immunity and B cell activation. To better understand how and why T cells select infected DCs rather than macrophages, we performed intravital microscopy and ex vivo analyses after infecting mice with vaccinia virus (VV), a large DNA virus that infects both LN macrophages and DCs. Although CD8(+) T cells interact with both infected macrophages and DCs in the LN peripheral interfollicular region (PIR), DCs generate more frequent and stable interactions with T cells. VV infection induces rapid release of CCR5-binding chemokines in the LN, and administration of chemokine-neutralizing antibodies diminishes T cell activation by increasing T cell localization to macrophages in the macrophage-rich region (MRR) at the expense of PIR DCs. Similarly, DC ablation increases both T cell localization to the MRR and the duration of T cell-macrophage contacts, resulting in suboptimal T cell activation. Thus, virus-induced chemokines in DLNs enable antiviral CD8(+) T cells to distinguish DCs from macrophages to optimize T cell priming.

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    ABSTRACT: Mounting a protective immune response is critically dependent on the orchestrated move-ment of cells within lymphoid tissues. The structure of secondary lymphoid organs reg-ulates immune responses by promoting optimal cell–cell and cell–extracellular matrix interactions. Naïve T cells are initially activated by antigen presenting cells in secondary lymphoid organs. Following priming, effector T cells migrate to the site of infection to exert their functions. Majority of the effector cells die while a small population of antigen-specific T cells persists as memory cells in distinct anatomical locations. The persistence and loca-tion of memory cells in lymphoid and non-lymphoid tissues is critical to protect the host from re-infection. The localization of memory T cells is carefully regulated by several fac-tors including the highly organized secondary lymphoid structure, the cellular expression of chemokine receptors and compartmentalized secretion of their cognate ligands. This bal-ance between the anatomy and the ordered expression of cell surface and soluble proteins regulates the subtle choreography of T cell migration. In recent years, our understanding of cellular dynamics of T cells has been advanced by the development of new imaging techniques allowing in situ visualization of T cell responses. Here, we review the past and more recent studies that have utilized sophisticated imaging technologies to investigate the migration dynamics of naïve, effector, and memory T cells. The ability to image the dynamics of T cell immune responses in situ has undergone significant advances over the past decade. For over a century, bright field transillumination or epifluorese-cence microscopy was the only technology utilized to image excised organ sections or to visualize cellular processes in vivo. These tech-niques were useful for visualizing leukocyte interactions with the endothelium (1–3). The introduction of immunohistochemistry and immunofluorescence coupled with the use of monoclonal antibodies introduced specificity to the staining of lymphocytes. More recently, the advent of integrated fluorescent probes (e.g., CFSE) or natural fluorescent proteins (e.g., green fluorescent pro-tein) permitted investigators to tag specific cell populations in vivo. These fluorescently labeled cells could now be tracked in real-time by directly imaging organs in explant preparations or directly intravitally in live animals. An overview of the techniques used for dynamic imaging of T cells is shown in Figure 1. A significant technological advance was achieved with the laser scanning confocal microscope (LSCM). This type of microscope uses a lens to focus the laser excitation light on the specimen and the emitted light from the focal plane is refocused trough the same lens to the center of an open detector aperture (pinhole). This innovation obstructs the light coming from above and below the focal plane and thus increases the resolution. Sharp optical sec-tioning through a specimen at different depths can be performed to produce a 3 dimensional reconstruction of the sample. How-ever, single photon confocal microcopy does not allow imaging at great depth (>100 µm) due to light scattering, photobleaching of stained tissue that is outside of the focal plane, and slow speed of data acquisition. Thus, it is very suitable for imaging thin tissues sections. Real-time dynamic imaging using LSCM is limited to the surface of the organ and for shorter periods of time. However, recent modifications to the standard single photon confocal micro-scope such as the addition of a microlens high speed spinning disk prevents cell damage and allows for rapid acquisition of imag-ing data of very large surfaces (approximately 870 µm × 660µm) (6). Thus, if deep tissue imaging is not required, the spinning disk confocal microscope can be very effective for performing dynamic imaging of large areas of various tissues. Several groups have recently used this technology for in vivo imaging, since it allows superior resolution (7). In a recent study, Cockburn and colleagues described the antigen-specific CD8+ T cell mediated killing of liver stage malaria parasites using a high speed spinning disk confocal microscope (7). In this case, even a superficial pene-tration of the laser beam was sufficient to observe the morphology of the liver parenchyma. Compared to conventional lower wavelength and single pho-ton excitation, the use of near-infrared two-photon (2P) exci-tation permits imaging of tissues at substantially greater depth (>300 µm). Moreover, the fact that the excitation of fluores-cent proteins is confined to the focal plane significantly mini-mizes the problem of photobleaching. Consequently, by using 2P microscopy it is now possible to visualize the dynamics of immune cells in real-time, and at greater depths in intact explanted tissues or in live animals without causing overt cellular damage (8). Read-ily available tissues like the skin and the associated draining lymph nodes (dLN) were among the first tissues that were imaged intrav-itally using elegant surgical techniques (Figure 1). More recently,
    Frontiers in Immunology 07/2014; DOI:10.13140/2.1.4684.6081
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    ABSTRACT: Chemokines are chemotactic cytokines that control the migratory patterns and positioning of all immune cells. Although chemokines were initially appreciated as important mediators of acute inflammation, we now know that this complex system of approximately 50 endogenous chemokine ligands and 20 G protein-coupled seven-transmembrane signaling receptors is also critical for the generation of primary and secondary adaptive cellular and humoral immune responses. Recent studies demonstrate important roles for the chemokine system in the priming of naive T cells, in cell fate decisions such as effector and memory cell differentiation, and in regulatory T cell function. In this review, we focus on recent advances in understanding how the chemokine system orchestrates immune cell migration and positioning at the organismic level in homeostasis, in acute inflammation, and during the generation and regulation of adoptive primary and secondary immune responses in the lymphoid system and peripheral nonlymphoid tissue.
    Annual Review of Immunology 03/2014; 32:659-702. DOI:10.1146/annurev-immunol-032713-120145 · 41.39 Impact Factor
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    ABSTRACT: Antigen derived from viral infections with influenza and vesicular stomatitis virus can persist after resolution of infection. Here we show that antigen can similarly persist for weeks following viral challenge and vaccination. Antigen is captured by lymphatic endothelial cells (LECs) under conditions that induce LEC proliferation. Consistent with published data showing that viral antigen persistence impacts the function of circulating memory T cells, we find that vaccine-elicited antigen persistence, found on LECs, positively influences the degree of protective immunity provided by circulating memory CD8(+) T cells. The coupling of LEC proliferation and antigen capture identifies a mechanism by which the LECs store, or 'archive', antigens for extended periods of time after antigen challenge, thereby increasing IFNγ/IL-2 production and enhancing protection against infection. These findings therefore have the potential to have an impact on future vaccination strategies and our understanding of the role for persisting antigen in both vaccine and infectious settings.
    Nature Communications 06/2014; 5:3989. DOI:10.1038/ncomms4989 · 10.74 Impact Factor

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