CD4
T cells integrate well-defined signals from the T-cell receptor (TCR) (signal 1) and a host of costimulatory molecules (signal 2) to initiate clonal expansion and differentiation into diverse ...functional T helper (Th) subsets. However, our ability to guide the expansion of context-appropriate Th subsets by deploying these signals in vaccination remains limited. Using cell-based vaccines, we selectively amplified signal 1 by exclusive presentation of an optimized peptide:MHC II (pMHC II) complex in the absence of classic costimulation. Contrary to expectations, amplified signal 1 alone was strongly immunogenic and selectively expanded high-affinity TCR clonotypes, despite delivering intense TCR signals. In contrast to natural infection or standard vaccines, amplified signal 1, presented by a variety of professional and nonprofessional antigen-presenting cells (APCs), induced exclusively polyfunctional Th1 effector and memory cells, which protected against retroviral infection and tumor challenge, and expanded tumor-reactive CD4
T cells otherwise rendered unresponsive in tumor-bearing hosts. Together, our findings uncover a default Th1 response to ample signal 1 and offer a means to selectively prime such protective responses by vaccination.
Follicular helper T cells (T
) mediate B cell selection and clonal expansion in germinal centers (GCs), and follicular regulatory T cells (T
) prevent the emergence of self-reactive B cells and help ...to extinguish the reaction. Here we show that GC reactions continually recruit T cells from both the naïve conventional and naive thymic regulatory T cell (Treg) repertoires. In the early GC, newly recruited T cells develop into T
, whereas cells entering during the contraction phase develop into T
cells that contribute to GC dissolution. The T
fate decision is associated with decreased antigen availability and is modulated by slow antigen delivery or mRNA vaccination. Thus, invasion of ongoing GCs by newly developing T
and T
helps remodel the GC based on antigen availability.
To explore the influence of genetics on homeostatic regulation of dendritic cell (DC) numbers, we present a screen of DCs and their progenitors in lymphoid and non-lymphoid tissues in Collaborative ...Cross (CC) and Diversity Outbred (DO) mice. We report 30 and 71 loci with logarithm of the odds (LOD) scores >8.18 and ranging from 6.67 to 8.19, respectively. The analysis reveals the highly polygenic and pleiotropic architecture of this complex trait, including many of the previously identified genetic regulators of DC development and maturation. Two SNPs in genes potentially underlying variation in DC homeostasis, a splice variant in Gramd4 (rs235532740) and a missense variant in Orai3 (rs216659754), are confirmed by gene editing using CRISPR-Cas9. Gramd4 is a central regulator of DC homeostasis that impacts the entire DC lineage, and Orai3 regulates cDC2 numbers in tissues. Overall, the data reveal a large number of candidate genes regulating DC homeostasis in vivo.
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•Collaborative Cross and Diversity Outbred mice show dendritic cell (DC) frequency variation•QTL mapping reveals the highly polygenic and pleiotropic architecture of DC homeostasis•Gramd4 and Orai3 regulate DC frequency
Oliveira et al. use quantitative trait locus (QTL) mapping in Diversity Outbred mice to find candidate genes linked to dendritic cell (DC) homeostasis. Site-directed mutagenesis using CRISPR-Cas9 confirms two candidate genes, Gramd4 and Orai3. Overall, the data represent a resource for interrogating the mechanisms governing DC homeostasis in tissues.
Antibody cloning from single B cells is an essential tool for characterizing humoral immune responses and obtaining valuable therapeutic and analytical reagents. Antibody cloning from individuals ...with high serologic titers to HIV-1, Influenza, Malaria and ZIKV has led to new insights that inform vaccine design efforts. In contrast to humans and mice, less is known about antibody cloning from single B cells in macaques. Here, we describe a protocol to identify and purify single antigen-specific macaque B cells, and subsequently clone and produce macaque monoclonal antibodies. The sorting strategy requires the use of a combination of fluorochrome labeled antigens and omission of anti-IgG antibodies that can interfere with antigen binding and vice versa. Optimized methods for macaque antibody gene amplification, DNA preparation for antibody production and antibody screening by ELISA are also presented.
•Design of sorting strategies to isolate HIV-1 Envelope-specific B cells.•Envelope baits and anti-isotype antibodies compete for binding to B cell receptor.•Method for next generation sequencing and cloning of macaque antibodies.•Cost-effective protocol to produce and screen monoclonal antibodies.
CD4+ T cells develop distinct and often contrasting helper, regulatory, or cytotoxic activities. Typically a property of CD8+ T cells, granzyme-mediated cytotoxic T cell (CTL) potential is also ...exerted by CD4+ T cells. However, the conditions that induce CD4+ CTLs are not entirely understood. Using single-cell transcriptional profiling, we uncover a unique signature of Granzyme B (GzmB)+ CD4+ CTLs, which distinguishes them from other CD4+ T helper (Th) cells, including Th1 cells, and strongly contrasts with the follicular helper T (Tfh) cell signature. The balance between CD4+ CTL and Tfh differentiation heavily depends on the class of infecting virus and is jointly regulated by the Tfh-related transcription factors Bcl6 and Tcf7 (encoding TCF-1) and by the expression of the inhibitory receptors PD-1 and LAG3. This unique profile of CD4+ CTLs offers targets for their study, and its antagonism by the Tfh program separates CD4+ T cells with either helper or killer functions.
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•Adenoviruses prime CD4 T cells with CTL potential, but retroviruses do not•CD4 CTLs are transcriptionally distinguishable from other Th cells•The CD4 CTL program is the direct opposite of the Tfh program•CD4 CTLs are restrained by the TCF-1-Bcl6 nexus and by PD-1 and LAG3
“Helper” CD4 T cells can also exhibit granzyme-mediated cytotoxicity. Donnarumma et al. investigate the conditions that induce CD4 CTLs and describe the dominant effect of the class of infecting virus. They uncover a unique transcriptional signature of CD4 CTLs and its multi-layered control.
Antigen receptor diversity underpins adaptive immunity by providing the ground for clonal selection of lymphocytes with the appropriate antigen reactivity. Current models attribute T cell clonal ...selection during the immune response to T-cell receptor (TCR) affinity for either foreign or self peptides. Here, we report that clonal selection of CD4(+) T cells is also extrinsically regulated by B cells. In response to viral infection, the antigen-specific TCR repertoire is progressively diversified by staggered clonotypic expansion, according to functional avidity, which correlates with self-reactivity. Clonal expansion of lower-avidity T-cell clonotypes depends on availability of MHC II-expressing B cells, in turn influenced by B-cell activation. B cells clonotypically diversify the CD4(+) T-cell response also to vaccination or tumour challenge, revealing a common effect.
The germinal centre is a dynamic microenvironment in which B cells that express high-affinity antibody variants produced by somatic hypermutation are selected for clonal expansion by limiting the ...numbers of T follicular helper cells
. Although much is known about the mechanisms that control the selection of B cells in the germinal centre, far less is understood about the clonal behaviour of the T follicular helper cells that help to regulate this process. Here we report on the dynamic behaviour of T follicular helper cell clones during the germinal centre reaction. We find that, similar to germinal centre B cells, T follicular helper cells undergo antigen-dependent selection throughout the germinal centre reaction that results in differential proliferative expansion and contraction. Increasing the amount of antigen presented in the germinal centre leads to increased division of T follicular helper cells. Competition between T follicular helper cell clones is mediated by the affinity of T cell receptors for peptide-major-histocompatibility-complex ligands. T cells that preferentially expand in the germinal centre show increased expression of genes downstream of the T cell receptor, such as those required for metabolic reprogramming, cell division and cytokine production. These dynamic changes lead to marked remodelling of the functional T follicular helper cell repertoire during the germinal centre reaction.
The germinal centre is a dynamic microenvironment in which B cells that express high-affinity antibody variants produced by somatic hypermutation are selected for clonal expansion by limiting the ...numbers of T follicular helper cells1,2. Although much is known about the mechanisms that control the selection of B cells in the germinal centre, far less is understood about the clonal behaviour of the T follicular helper cells that help to regulate this process. Here we report on the dynamic behaviour of T follicular helper cell clones during the germinal centre reaction. We find that, similar to germinal centre B cells, T follicular helper cells undergo antigen-dependent selection throughout the germinal centre reaction that results in differential proliferative expansion and contraction. Increasing the amount of antigen presented in the germinal centre leads to increased division of T follicular helper cells. Competition between T follicular helper cell clones is mediated by the affinity of T cell receptors for peptide-major-histocompatibility-complex ligands. T cells that preferentially expand in the germinal centre show increased expression of genes downstream ofthe T cell receptor, such as those required for metabolic reprogramming, cell division and cytokine production. These dynamic changes lead to marked remodelling of the functional T follicular helper cell repertoire during the germinal centre reaction.
Broadly neutralizing monoclonal antibodies protect against infection with HIV-1 in animal models, suggesting that a vaccine that elicits these antibodies would be protective in humans. However, it ...has not yet been possible to induce adequate serological responses by vaccination. Here, to activate B cells that express precursors of broadly neutralizing antibodies within polyclonal repertoires, we developed an immunogen, RC1, that facilitates the recognition of the variable loop 3 (V3)-glycan patch on the envelope protein of HIV-1. RC1 conceals non-conserved immunodominant regions by the addition of glycans and/or multimerization on virus-like particles. Immunization of mice, rabbits and rhesus macaques with RC1 elicited serological responses that targeted the V3-glycan patch. Antibody cloning and cryo-electron microscopy structures of antibody-envelope complexes confirmed that immunization with RC1 expands clones of B cells that carry the anti-V3-glycan patch antibodies, which resemble precursors of human broadly neutralizing antibodies. Thus, RC1 may be a suitable priming immunogen for sequential vaccination strategies in the context of polyclonal repertoires.
Best known for presenting antigenic peptides to CD4+ T cells, major histocompatibility complex class II (MHC II) also transmits or may modify intracellular signals. Here, we show that MHC II ...cell-autonomously regulates the balance between self-renewal and differentiation in B-cell precursors, as well as in malignant B cells. Initiation of MHC II expression early during bone marrow B-cell development limited the occupancy of cycling compartments by promoting differentiation, thus regulating the numerical output of B cells. MHC II deficiency preserved stem cell characteristics in developing pro-B cells in vivo, and ectopic MHC II expression accelerated hematopoietic stem cell differentiation in vitro. Moreover, MHC II expression restrained growth of murine B-cell leukemia cell lines in vitro and in vivo, independently of CD4+ T-cell surveillance. Our results highlight an important cell-intrinsic contribution of MHC II expression to establishing the differentiated B-cell phenotype.
•MHC II cell-autonomously regulates self-renewal and differentiation in developing B-cell precursors.•MHC II expression restrains growth of B-cell leukemias in vitro and in vivo, independent of CD4+ T-cell surveillance.
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