The transcription factor BATF is required for the differentiation of interleukin 17 (IL-17)-producing helper T cells (TH17 cells) and follicular helper T cells (TFH cells). Here we identified a ...fundamental role for BATF in regulating the differentiation of effector of CD8(+) T cells. BATF-deficient CD8(+) T cells showed profound defects in effector population expansion and underwent proliferative and metabolic catastrophe early after encountering antigen. BATF, together with the transcription factors IRF4 and Jun proteins, bound to and promoted early expression of genes encoding lineage-specific transcription-factors (T-bet and Blimp-1) and cytokine receptors while paradoxically repressing genes encoding effector molecules (IFN-γ and granzyme B). Thus, BATF amplifies T cell antigen receptor (TCR)-dependent expression of transcription factors and augments the propagation of inflammatory signals but restrains the expression of genes encoding effector molecules. This checkpoint prevents irreversible commitment to an effector fate until a critical threshold of downstream transcriptional activity has been achieved.
Exhausted T cells express multiple co-inhibitory molecules that impair their function and limit immunity to chronic viral infection. Defining novel markers of exhaustion is important both for ...identifying and potentially reversing T cell exhaustion. Herein, we show that the ectonucleotidse CD39 is a marker of exhausted CD8+ T cells. CD8+ T cells specific for HCV or HIV express high levels of CD39, but those specific for EBV and CMV do not. CD39 expressed by CD8+ T cells in chronic infection is enzymatically active, co-expressed with PD-1, marks cells with a transcriptional signature of T cell exhaustion and correlates with viral load in HIV and HCV. In the mouse model of chronic Lymphocytic Choriomeningitis Virus infection, virus-specific CD8+ T cells contain a population of CD39high CD8+ T cells that is absent in functional memory cells elicited by acute infection. This CD39high CD8+ T cell population is enriched for cells with the phenotypic and functional profile of terminal exhaustion. These findings provide a new marker of T cell exhaustion, and implicate the purinergic pathway in the regulation of T cell exhaustion.
The PD-1 pathway regulates dysfunctional T cells in chronic infection and cancer, but the role of this pathway during acute infection remains less clear. Here, we demonstrate that PD-1 signals are ...needed for optimal memory. Mice deficient in the PD-1 pathway exhibit impaired CD8+ T cell memory following acute influenza infection, including reduced virus-specific CD8+ T cell numbers and compromised recall responses. PD-1 blockade during priming leads to similar differences early post-infection but without the defect in memory formation, suggesting that timing and/or duration of PD-1 blockade could be tailored to modulate host responses. Our studies reveal a role for PD-1 as an integrator of CD8+ T cell signals that promotes CD8+ T cell memory formation and suggest PD-1 continues to fine-tune CD8+ T cells after they migrate into non-lymphoid tissues. These findings have important implications for PD-1-based immunotherapy, in which PD-1 inhibition may influence memory responses in patients.
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•Early loss of PD-1 leads to overactivation of CD8+ T cells during acute infection•Mice constitutively lacking PD-1 or PD-L develop impaired CD8+ T cell memory•Cell-intrinsic PD-1 signals suppress effector cell expansion and promote memory•Timing of PD-1 blockade determines impact on memory generation
The role of PD-1 in memory development is poorly understood. Here, Pauken et al. show that constitutive loss of PD-1 during acute infection causes overactivation of CD8+ T cells during the effector phase and impairs memory and recall responses. These data indicate PD-1 is required for optimal memory.
Lymph node fibroblastic reticular cells (FRCs) respond to signals from activated T cells by releasing nitric oxide, which inhibits T cell proliferation and restricts the size of the expanding T cell ...pool. Whether interactions with FRCs also support the function or differentiation of activated CD8
T cells is not known. Here we report that encounters with FRCs enhanced cytokine production and remodeled chromatin accessibility in newly activated CD8
T cells via interleukin-6. These epigenetic changes facilitated metabolic reprogramming and amplified the activity of pro-survival pathways through differential transcription factor activity. Accordingly, FRC conditioning significantly enhanced the persistence of virus-specific CD8
T cells in vivo and augmented their differentiation into tissue-resident memory T cells. Our study demonstrates that FRCs play a role beyond restricting T cell expansion-they can also shape the fate and function of CD8
T cells.
The T cell costimulatory receptor CD28 is required for the full activation of naïve T cells and for the development and maintenance of Foxp3(+) regulatory T (Treg) cells. We showed that the ...cytoplasmic domain of CD28 was bound to the plasma membrane in resting cells and that ligand binding to CD28 resulted in its release. Membrane binding by the CD28 cytoplasmic domain required two clusters of basic amino acid residues, which interacted with the negatively charged inner leaflet of the plasma membrane. These same clusters of basic residues also served as interaction sites for Lck, a Src family kinase critical for CD28 function. This signaling complex was further stabilized by the Lck-mediated phosphorylation of CD28 Tyr(207) and the subsequent binding of the Src homology 2 (SH2) domain of Lck to this phosphorylated tyrosine. Mutation of the basic clusters in the CD28 cytoplasmic domain reduced the recruitment to the CD28-Lck complex of protein kinase Cθ (PKCθ), which serves as a key effector kinase in the CD28 signaling pathway. Consequently, mutation of either a basic cluster or Tyr(207) impaired CD28 function in mice as shown by the reduced thymic differentiation of FoxP3(+) Treg cells. On the basis of these results, we propose a previously undescribed model for the initiation of CD28 signaling.
Significance Effector CD8 ⁺ T-cell differentiation is essential for protective immunity. Investigating specific genes in this process by knockdown with RNAi is challenging because naive T cells are ...refractory to viral transduction. To overcome this obstacle, we developed a novel strategy to knock down genes in naive CD8 ⁺ T cells by creating bone marrow chimera from hematopoietic progenitors transduced with an inducible shRNA. This approach enabled inducible in vivo gene knockdown in any cell type developed from this progenitor pool. We applied this strategy to show that the transcription factor BATF is essential for initial commitment to effector differentiation but becomes dispensable by 72 h. This approach now enables the study of gene function in vivo in cells of hematopoietic origin otherwise refractory to viral transduction.
The differentiation of effector CD8 ⁺ T cells is critical for the development of protective responses to pathogens and for effective vaccines. In the first few hours after activation, naive CD8 ⁺ T cells initiate a transcriptional program that leads to the formation of effector and memory T cells, but the regulation of this process is poorly understood. Investigating the role of specific transcription factors (TFs) in determining CD8 ⁺ effector T-cell fate by gene knockdown with RNAi is challenging because naive T cells are refractory to transduction with viral vectors without extensive ex vivo stimulation, which obscures the earliest events in effector differentiation. To overcome this obstacle, we developed a novel strategy to test the function of genes in naive CD8 ⁺ T cells in vivo by creating bone marrow chimera from hematopoietic progenitors transduced with an inducible shRNA construct. Following hematopoietic reconstitution, this approach allowed inducible in vivo gene knockdown in any cell type that developed from this transduced progenitor pool. We demonstrated that lentivirus-transduced progenitor cells could reconstitute normal hematopoiesis and develop into naive CD8 ⁺ T cells that were indistinguishable from wild-type naive T cells. This experimental system enabled induction of efficient gene knockdown in vivo without subsequent manipulation. We applied this strategy to show that the TF BATF is essential for initial commitment of naive CD8 ⁺ T cells to effector development but becomes dispensable by 72h. This approach makes possible the study of gene function in vivo in unperturbed cells of hematopoietic origin that are refractory to viral transduction.
Follicular Tregs (Tfr cells) inhibit antibody production, whereas follicular Th cells (Tfh cells) stimulate it. Tfr cells are found in blood; however, relatively little is known about the ...developmental signals for these cells or their functions. Here we demonstrated that circulating Tfr and Tfh cells share properties of memory cells and are distinct from effector Tfr and Tfh cells found within lymph nodes (LNs). Circulating memory-like Tfh cells were potently reactivated by DCs, homed to germinal centers, and produced more cytokines than did effector LN Tfh cells. Circulating memory-like Tfr cells persisted for long periods of time in vivo and homed to germinal centers after reactivation. Effector LN Tfr cells suppressed Tfh cell activation and production of cytokines, including IL-21, and inhibited class switch recombination and B cell activation. The suppressive function of this population was not dependent on specific antigen. Similar to LN effector Tfr cells, circulating Tfr cells also suppressed B and Tfh cells, but with a much lower capacity. Our data indicate that circulating memory-like Tfr cells are less suppressive than LN Tfr cells and circulating memory-like Tfh cells are more potent than LN effector Tfh cells; therefore, these circulating populations can provide rapid and robust systemic B cell help during secondary antigen exposure.
Gene-expression profiling has become a mainstay in immunology, but subtle changes in gene networks related to biological processes are hard to discern when comparing various datasets. For instance, ...conservation of the transcriptional response to sepsis in mouse models and human disease remains controversial. To improve transcriptional analysis in immunology, we created ImmuneSigDB: a manually annotated compendium of ∼5,000 gene-sets from diverse cell states, experimental manipulations, and genetic perturbations in immunology. Analysis using ImmuneSigDB identified signatures induced in activated myeloid cells and differentiating lymphocytes that were highly conserved between humans and mice. Sepsis triggered conserved patterns of gene expression in humans and mouse models. However, we also identified species-specific biological processes in the sepsis transcriptional response: although both species upregulated phagocytosis-related genes, a mitosis signature was specific to humans. ImmuneSigDB enables granular analysis of transcriptomic data to improve biological understanding of immune processes of the human and mouse immune systems.
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•ImmuneSigDB: Collection of ∼5,000 gene sets derived from ∼400 immunological studies•Includes a wide range of mouse and human immune cell states and perturbations•Designed for use with GSEA and an approach called Leading Edge Metagene analysis•ImmuneSigDB identified shared and unique biology in human and mouse sepsis response
Meaningful interpretation of gene-expression analyses relies on identifying changes in expression of sets of genes corresponding to specific biological processes and cell states. Haining and colleagues generated a collection of ∼5,000 annotated, immunology-specific gene sets and uncovered shared and species-specific biology in mouse and human transcriptional responses to sepsis.
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