Antibodies play a crucial role in virus control. The production of antibodies requires virus-specific B cells to encounter viral antigens in lymph nodes, become activated, interact with different ...immune cells, proliferate and enter specific differentiation programmes. Each step occurs in distinct lymph node niches, requiring a coordinated migration of B cells between different subcompartments. The development of multiphoton intravital microscopy has enabled researchers to begin to elucidate the precise cellular and molecular events by which lymph nodes coordinate humoral responses. This Review discusses recent studies that clarify how viruses interfere with antibody responses, highlighting how these mechanisms relate to our topological and temporal understanding of B cell activation within secondary lymphoid organs.
Strategically positioned along lymphatic vessels, lymph nodes act as filter stations preventing systemic pathogen dissemination; they are primary sites of innate immune responses and provide the ...staging grounds for the generation of adaptive immunity. Critical mediators of these lymph node functions are two phenotypically and functionally distinct subsets of macrophages: the subcapsular sinus macrophages and the medullary macrophages. This review focuses on the phenotype and function of these lymph node sinus‐resident macrophages and summarizes methods for their proper identification and experimental manipulation.
Differentiation of CD4
T cells into either follicular helper T (T
) or type 1 helper T (T
1) cells influences the balance between humoral and cellular adaptive immunity, but the mechanisms whereby ...pathogens elicit distinct effector cells are incompletely understood. Here we analyzed the spatiotemporal dynamics of CD4
T cells during infection with recombinant vesicular stomatitis virus (VSV), which induces early, potent neutralizing antibodies, or recombinant lymphocytic choriomeningitis virus (LCMV), which induces a vigorous cellular response but inefficient neutralizing antibodies, expressing the same T cell epitope. Early exposure of dendritic cells to type I interferon (IFN), which occurred during infection with VSV, induced production of the cytokine IL-6 and drove T
cell polarization, whereas late exposure to type I IFN, which occurred during infection with LCMV, did not induce IL-6 and allowed differentiation into T
1 cells. Thus, tight spatiotemporal regulation of type I IFN shapes antiviral CD4
T cell differentiation and might instruct vaccine design strategies.
Immunoglobulin M (IgM) is the first type of antibody produced during acute infections and thus provides an early line of specific defense against pathogens. Being produced in secondary lymphoid ...organs, IgM must rapidly be exported to the blood circulation. However, it is currently unknown how such large pentameric molecules are released from lymph nodes (LNs). Here, we show that upon immunization, IgM transiently gains access to the luminal side of the conduit system, a reticular infrastructure enabling fast delivery of tissue-derived soluble substances to the LN parenchyma. Using microinjections of purified IgM, we demonstrate that conduit-associated IgM is delivered by neither the afferent lymph nor the blood, but is locally conveyed by conduits. Exploiting in vivo models, we further demonstrate that conduit-associated IgM is locally and transiently produced by activated, antigen-specific B cells migrating in the T cell zone. Thus, our study reveals that the conduit system is coopted by B cells to rapidly export secreted IgM out of LNs.
Protection from viral infections depends on immunoglobulin isotype switching, which endows antibodies with effector functions. Here, we find that the protein kinase DYRK1A is essential for B ...cell-mediated protection from viral infection and effective vaccination through regulation of class switch recombination (CSR). Dyrk1a-deficient B cells are impaired in CSR activity in vivo and in vitro. Phosphoproteomic screens and kinase-activity assays identify MSH6, a DNA mismatch repair protein, as a direct substrate for DYRK1A, and deletion of a single phosphorylation site impaired CSR. After CSR and germinal center (GC) seeding, DYRK1A is required for attenuation of B cell proliferation. These findings demonstrate DYRK1A-mediated biological mechanisms of B cell immune responses that may be used for therapeutic manipulation in antibody-mediated autoimmunity.
Tr1 cell therapy is considered an emerging approach to improve transplant tolerance and enhance allogeneic graft survival. However, it remains unclear how Tr1 cells promote transplant tolerance and ...whether they will be safe and stable in the face of an acute viral infection. By employing a mouse model of pancreatic islet transplantation, we report that Tr1 cell therapy promoted transplant tolerance via de novo induction of Tr1 cells in the recipients. Acute viral infection with lymphocytic choriomeningitis virus (LCMV) had no impact on Tr1 cell number and function, neither on the Tr1 cells infused nor on the ones induced, and that was reflected in the robust maintenance of the graft. Moreover, Tr1 cell immunotherapy had no detrimental effect on CD8 and CD4 anti‐LCMV effector T‐cell responses and viral control. Together, these data suggest that Tr1 cells did not convert to effector cells during acute infection with LCMV, maintained transplant tolerance and did not inhibit antiviral immunity.
Tr1 cell immunotherapy induces transplant tolerance to pancreatic islets via the de novo induction of Tr1 cells in the spleen. Tolerance established via Tr1 cell immunotherapy does not inhibit acute antiviral T‐cell responses. Viral Infection does not break transplant tolerance established by Tr1 cell immunotherapy.
Humoral and cellular responses to viral infections coexist in a dynamic equilibrium that often results in efficient viral clearance. However, in some infections one of the two responses prevails, for ...instance when an overactivation of cytotoxic T cells is accompanied by weak and insufficient antibody responses. Although the cellular response is usually sufficient to control a primary viral infection, in some cases clearance is not complete and persistent infections ensue. In order to design effective therapeutic or vaccination strategies aiming at inducing early and potent neutralizing antibody responses, a deep knowledge of the cellular and molecular determinants of antiviral immune responses is needed. Here, we review our understanding on the spatiotemporal dynamics of antiviral humoral immune responses, with a particular focus on recent studies using intravital imaging approaches as an insightful complement to more traditional techniques.
•CXCR5+ CD8 T cells have been identified in chronic viral infections showing heightened proliferative and cytotoxic properties as compared to CXCR5- CD8 T cells.•CXCR5+ CD8 T cells have been ...identified in mice with mutations in immunoregulatory genes (e.g. scurfy mice) showing Tfh-like properties promoting humoral autoimmunity.•CXCR5+ CD8 T cells can function as regulatory T cells that inhibit CD4 T follicular helper (Tfh) humoral responses and the development of autoantibodies in certain mouse models.
Our knowledge on the development and functions of CXCR5+ CD8 T cells is rudimentary when confronted to other extensively studied CD8 T cell subsets. A decade ago, it became apparent that CD8 T cells possess two additional and rather unexpected functional properties other than cytotoxicity, one involving what is known as B cell helper activity and the other involving suppression of self-reactive responses generally known as T cell regulation. Although these adaptive responses are well-known functions of CD4 T cells, they remain poorly understood in CD8 T cells. Thus far, three subsets of CXCR5+ CD8 T cells have been identified. The first subset of CXCR5+ CD8 T cells is present in chronic viral infections and is referred to as progenitors of exhausted T cells showing heightened proliferative and cytotoxic properties as compared to CXCR5- CD8 T cells. The second subset of CXCR5+ CD8 T cells functions as regulatory T cells that inhibit CD4 T follicular helper (Tfh) humoral responses and the development of autoantibodies. The third subset of CXCR5+ CD8 T cells was identified in mice with mutations in immunoregulatory genes (i.e. FOXP3 and IL-2-deficient mice) and involves CD8 T cells with Tfh-like properties that promote humoral autoimmunity through interaction with B cells. This review summarizes the phenotype, function, and differentiation of CXCR5+ CD8 T cells.
Here, we provide detailed protocols for the isolation of mouse Kupffer cells – the liver-resident macrophages – for phenotypic (e.g., via flow cytometry, mass cytometry, or RNA-sequencing) analyses ...or for functional experiments involving cell culture. The procedures presented can be adapted for the isolation of other hepatic cell populations.
For complete details on the use and execution of this protocol, please refer to De Simone et al. (2021).
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•Protocol for Kupffer cell (KC) isolation•Suitable for the simultaneous isolation of other hepatic cell populations•Isolated KCs are suitable for phenotypic and functional analyses•We provide critical tips for cell processing and FACS-based sorting
Here, we provide detailed protocols for the isolation of mouse Kupffer cells – the liver-resident macrophages – for phenotypic (e.g., via flow cytometry, mass cytometry or RNA-sequencing) analyses or for functional experiments involving cell culture. The procedures presented can be adapted for the isolation of other hepatic cell populations.
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