RESUMO
For many infections and almost all vaccines, neutralizing-antibody-mediated immunity is the primary basis and best functional correlate of immunological protection. Durable long-term humoral immunity is mediated by antibodies secreted by plasma cells that preexist subsequent exposures and by memory B cells that rapidly respond to infections once they have occurred. In the midst of the current pandemic of coronavirus disease 2019, it is important to define our current understanding of the unique roles of memory B cells and plasma cells in immunity and the factors that control the formation and persistence of these cell types. This fundamental knowledge is the basis to interpret findings from natural infections and vaccines. Here, we review transcriptional and metabolic programs that promote and support B cell fates and functions, suggesting points at which these pathways do and do not intersect.
Assuntos
Linfócitos B/imunologia , Linfócitos B/metabolismo , Metabolismo Energético , Regulação da Expressão Gênica , Memória Imunológica , Plasmócitos/imunologia , Plasmócitos/metabolismo , Animais , Biomarcadores , Diferenciação Celular/genética , Diferenciação Celular/imunologia , Sobrevivência Celular/genética , Sobrevivência Celular/imunologia , Centro Germinativo/imunologia , Centro Germinativo/metabolismo , Humanos , Memória Imunológica/genética , Ativação Linfocitária/genética , Ativação Linfocitária/imunologia , Transcrição GênicaRESUMO
Maintenance of immunological self-tolerance requires lymphocytes carrying self-reactive antigen receptors to be selectively prevented from mounting destructive or inflammatory effector responses. Classically, self-tolerance is viewed in terms of the removal, editing, or silencing of B and T cells that have formed self-reactive antigen receptors during their early development. However, B cells activated by foreign antigen can enter germinal centers (GCs), where they further modify their antigen receptor by somatic hypermutation (SHM) of their immunoglobulin genes. The inevitable emergence of activated, self-reactive GC B cells presents a unique challenge to the maintenance of self-tolerance that must be rapidly countered to avoid autoantibody production. Here we discuss current knowledge of the mechanisms that enforce B cell self-tolerance, with particular focus on the control of self-reactive GC B cells. We also consider how self-reactive GC B cells can escape self-tolerance to initiate autoantibody production or instead be redeemed via SHM and used in productive antibody responses.
Assuntos
Autoimunidade , Linfócitos B/imunologia , Centro Germinativo/imunologia , Animais , Autoanticorpos/imunologia , Autoantígenos/imunologia , Linfócitos B/metabolismo , Centro Germinativo/metabolismo , Humanos , Tolerância Imunológica , Ativação Linfocitária/genética , Ativação Linfocitária/imunologia , Plasmócitos/imunologia , Plasmócitos/metabolismo , Subpopulações de Linfócitos T/imunologia , Subpopulações de Linfócitos T/metabolismoRESUMO
Peripheral sensory neurons widely innervate various tissues to continuously monitor and respond to environmental stimuli. Whether peripheral sensory neurons innervate the spleen and modulate splenic immune response remains poorly defined. Here, we demonstrate that nociceptive sensory nerve fibers extensively innervate the spleen along blood vessels and reach B cell zones. The spleen-innervating nociceptors predominantly originate from left T8-T13 dorsal root ganglia (DRGs), promoting the splenic germinal center (GC) response and humoral immunity. Nociceptors can be activated by antigen-induced accumulation of splenic prostaglandin E2 (PGE2) and then release calcitonin gene-related peptide (CGRP), which further promotes the splenic GC response at the early stage. Mechanistically, CGRP directly acts on B cells through its receptor CALCRL-RAMP1 via the cyclic AMP (cAMP) signaling pathway. Activating nociceptors by ingesting capsaicin enhances the splenic GC response and anti-influenza immunity. Collectively, our study establishes a specific DRG-spleen sensory neural connection that promotes humoral immunity, suggesting a promising approach for improving host defense by targeting the nociceptive nervous system.
Assuntos
Peptídeo Relacionado com Gene de Calcitonina , Centro Germinativo , Imunidade Humoral , Baço , Animais , Masculino , Camundongos , Linfócitos B/imunologia , Linfócitos B/metabolismo , Peptídeo Relacionado com Gene de Calcitonina/metabolismo , Capsaicina/farmacologia , AMP Cíclico/metabolismo , Dinoprostona/metabolismo , Gânglios Espinais/metabolismo , Centro Germinativo/imunologia , Camundongos Endogâmicos C57BL , Nociceptores/metabolismo , Proteína 1 Modificadora da Atividade de Receptores/metabolismo , Células Receptoras Sensoriais/metabolismo , Células Receptoras Sensoriais/efeitos dos fármacos , Transdução de Sinais , Baço/inervação , Baço/imunologia , FemininoRESUMO
Although T cell help for B cells was described several decades ago, it was the identification of CXCR5 expression by B follicular helper T (Tfh) cells and the subsequent discovery of their dependence on BCL6 that led to the recognition of Tfh cells as an independent helper subset and accelerated the pace of discovery. More than 20 transcription factors, together with RNA-binding proteins and microRNAs, control the expression of chemotactic receptors and molecules important for the function and homeostasis of Tfh cells. Tfh cells prime B cells to initiate extrafollicular and germinal center antibody responses and are crucial for affinity maturation and maintenance of humoral memory. In addition to the roles that Tfh cells have in antimicrobial defense, in cancer, and as HIV reservoirs, regulation of these cells is critical to prevent autoimmunity. The realization that follicular T cells are heterogeneous, comprising helper and regulatory subsets, has raised questions regarding a possible division of labor in germinal center B cell selection and elimination.
Assuntos
Linfócitos B/imunologia , Centro Germinativo/imunologia , Imunidade Humoral , Subpopulações de Linfócitos T/imunologia , Linfócitos T Auxiliares-Indutores/imunologia , Animais , Diferenciação Celular , Regulação da Expressão Gênica , Humanos , Memória Imunológica , Ativação Linfocitária , MicroRNAs/genética , Proteínas Proto-Oncogênicas c-bcl-6/metabolismo , Receptores CXCR5/metabolismoRESUMO
Germinal centers (GCs) form in secondary lymphoid organs in response to infection and immunization and are the source of affinity-matured B cells. The duration of GC reactions spans a wide range, and long-lasting GCs (LLGCs) are potentially a source of highly mutated B cells. We show that rather than consisting of continuously evolving B cell clones, LLGCs elicited by influenza virus or SARS-CoV-2 infection in mice are sustained by progressive replacement of founder clones by naive-derived invader B cells that do not detectably bind viral antigens. Rare founder clones that resist replacement for long periods are enriched in clones with heavily mutated immunoglobulins, including some with very high affinity for antigen, that can be recalled by boosting. Our findings reveal underappreciated aspects of the biology of LLGCs generated by respiratory virus infection and identify clonal replacement as a potential constraint on the development of highly mutated antibodies within these structures.
Assuntos
Linfócitos B , Centro Germinativo , Infecções por Vírus de RNA , Animais , Camundongos , Linfócitos B/citologia , Linfócitos B/imunologia , Células Clonais , COVID-19 , Centro Germinativo/citologia , Centro Germinativo/imunologia , SARS-CoV-2 , Influenza Humana , Infecções por Vírus de RNA/imunologia , Infecções por Vírus de RNA/patologia , Infecções por Vírus de RNA/virologiaRESUMO
SARS-CoV-2 mRNA vaccines induce robust anti-spike (S) antibody and CD4+ T cell responses. It is not yet clear whether vaccine-induced follicular helper CD4+ T (TFH) cell responses contribute to this outstanding immunogenicity. Using fine-needle aspiration of draining axillary lymph nodes from individuals who received the BNT162b2 mRNA vaccine, we evaluated the T cell receptor sequences and phenotype of lymph node TFH. Mining of the responding TFH T cell receptor repertoire revealed a strikingly immunodominant HLA-DPB1∗04-restricted response to S167-180 in individuals with this allele, which is among the most common HLA alleles in humans. Paired blood and lymph node specimens show that while circulating S-specific TFH cells peak one week after the second immunization, S-specific TFH persist at nearly constant frequencies for at least six months. Collectively, our results underscore the key role that robust TFH cell responses play in establishing long-term immunity by this efficacious human vaccine.
Assuntos
COVID-19/imunologia , COVID-19/virologia , Imunidade/imunologia , SARS-CoV-2/imunologia , Células T Auxiliares Foliculares/imunologia , Vacinação , Vacinas Sintéticas/imunologia , Vacinas de mRNA/imunologia , Adulto , Linfócitos B/imunologia , Vacina BNT162/imunologia , COVID-19/sangue , Células Clonais , Estudos de Coortes , Citocinas/metabolismo , Feminino , Centro Germinativo/imunologia , Cadeias beta de HLA-DP/imunologia , Humanos , Epitopos Imunodominantes/imunologia , Células Jurkat , Linfonodos/metabolismo , Masculino , Pessoa de Meia-Idade , Peptídeos/química , Peptídeos/metabolismo , Multimerização Proteica , Receptores de Antígenos de Linfócitos T/metabolismoRESUMO
Affinity-matured plasma cells (PCs) of varying lifespans are generated through a germinal center (GC) response. The developmental dynamics and genomic programs of antigen-specific PC precursors remain to be elucidated. Here, using a model antigen in mice, we demonstrate biphasic generation of PC precursors, with those generating long-lived bone marrow PCs preferentially produced in the late phase of GC response. Clonal tracing using single-cell RNA sequencing and B cell antigen receptor sequencing in spleen and bone marrow compartments, coupled with adoptive transfer experiments, reveals a new PC transition state that gives rise to functionally competent PC precursors. The latter undergo clonal expansion, dependent on inducible expression of TIGIT. We propose a model for the proliferation and programming of precursors of long-lived PCs, based on extended antigen encounters in the GC.
Assuntos
Diferenciação Celular , Centro Germinativo , Plasmócitos , Animais , Plasmócitos/imunologia , Plasmócitos/metabolismo , Camundongos , Centro Germinativo/imunologia , Receptores de Antígenos de Linfócitos B/metabolismo , Receptores de Antígenos de Linfócitos B/genética , Camundongos Endogâmicos C57BL , Receptores Imunológicos/metabolismo , Receptores Imunológicos/genética , Camundongos TransgênicosRESUMO
The immunological mechanisms underlying chronic colitis are poorly understood. T follicular helper (TFH) cells are critical in helping B cells during germinal center reactions. In a T cell transfer colitis model, a lymphoid structure composed of mature dendritic cells (DCs) and TFH cells was found within T cell zones of colonic lymphoid follicles. TFH cells were required for mature DC accumulation, the formation of DC-T cell clusters and colitis development. Moreover, DCs promoted TFH cell differentiation, contributing to colitis development. A lineage-tracing analysis showed that, following migration to the lamina propria, TFH cells transdifferentiated into long-lived pathogenic TH1 cells, promoting colitis development. Our findings have therefore demonstrated the reciprocal regulation of TFH cells and DCs in colonic lymphoid follicles, which is critical in chronic colitis pathogenesis.
Assuntos
Diferenciação Celular , Colite , Células Dendríticas , Células T Auxiliares Foliculares , Animais , Células Dendríticas/imunologia , Colite/imunologia , Colite/patologia , Células T Auxiliares Foliculares/imunologia , Camundongos , Diferenciação Celular/imunologia , Camundongos Endogâmicos C57BL , Modelos Animais de Doenças , Células Th1/imunologia , Colo/imunologia , Colo/patologia , Camundongos Knockout , Centro Germinativo/imunologia , Camundongos TransgênicosRESUMO
Current prophylactic human immunodeficiency virus 1 (HIV-1) vaccine research aims to elicit broadly neutralizing antibodies (bnAbs). Membrane-proximal external region (MPER)-targeting bnAbs, such as 10E8, provide exceptionally broad neutralization, but some are autoreactive. Here, we generated humanized B cell antigen receptor knock-in mouse models to test whether a series of germline-targeting immunogens could drive MPER-specific precursors toward bnAbs. We found that recruitment of 10E8 precursors to germinal centers (GCs) required a minimum affinity for germline-targeting immunogens, but the GC residency of MPER precursors was brief due to displacement by higher-affinity endogenous B cell competitors. Higher-affinity germline-targeting immunogens extended the GC residency of MPER precursors, but robust long-term GC residency and maturation were only observed for MPER-HuGL18, an MPER precursor clonotype able to close the affinity gap with endogenous B cell competitors in the GC. Thus, germline-targeting immunogens could induce MPER-targeting antibodies, and B cell residency in the GC may be regulated by a precursor-competitor affinity gap.
Assuntos
Afinidade de Anticorpos , Linfócitos B , Centro Germinativo , Anticorpos Anti-HIV , HIV-1 , Centro Germinativo/imunologia , Animais , Camundongos , Humanos , Linfócitos B/imunologia , HIV-1/imunologia , Anticorpos Anti-HIV/imunologia , Afinidade de Anticorpos/imunologia , Anticorpos Neutralizantes/imunologia , Infecções por HIV/imunologia , Vacinas contra a AIDS/imunologia , Receptores de Antígenos de Linfócitos B/metabolismo , Receptores de Antígenos de Linfócitos B/imunologia , Técnicas de Introdução de Genes , Camundongos Transgênicos , Anticorpos Amplamente Neutralizantes/imunologia , Camundongos Endogâmicos C57BLRESUMO
While some infections elicit germinal centers, others produce only extrafollicular responses. The mechanisms controlling these dichotomous fates are poorly understood. We identify IL-12 as a cytokine switch, acting directly on B cells to promote extrafollicular and suppress germinal center responses. IL-12 initiates a B cell-intrinsic feed-forward loop between IL-12 and IFNγ, amplifying IFNγ production, which promotes proliferation and plasmablast differentiation from mouse and human B cells, in synergy with IL-12. IL-12 sustains the expression of a portion of IFNγ-inducible genes. Together, they also induce unique gene changes, reflecting both IFNγ amplification and cooperative effects between both cytokines. In vivo, cells lacking both IL-12 and IFNγ receptors are more impaired in plasmablast production than those lacking either receptor alone. Further, B cell-derived IL-12 enhances both plasmablast responses and T helper 1 cell commitment. Thus, B cell-derived IL-12, acting on T and B cells, determines the immune response mode, with implications for vaccines, pathogen protection and autoimmunity.
Assuntos
Linfócitos B , Diferenciação Celular , Centro Germinativo , Interferon gama , Interleucina-12 , Animais , Interleucina-12/imunologia , Interleucina-12/metabolismo , Camundongos , Interferon gama/metabolismo , Interferon gama/imunologia , Centro Germinativo/imunologia , Humanos , Linfócitos B/imunologia , Linfócitos B/metabolismo , Diferenciação Celular/imunologia , Camundongos Knockout , Camundongos Endogâmicos C57BL , Plasmócitos/imunologia , Plasmócitos/metabolismo , Ativação Linfocitária/imunologia , Receptores de Interferon/metabolismo , Receptores de Interferon/genética , Células Cultivadas , Proliferação de CélulasRESUMO
Memory B cells (MBCs) differentiate into plasma cells (PCs) or germinal centers (GCs) upon antigen recall. How this decision is programmed is not understood. We found that the relative strength between two antagonistic transcription factors, B lymphocyte-induced maturation protein 1 (BLIMP1) and BTB domain and CNC homolog 2 (BACH2), progressively increases in favor of BLIMP1 in antigen-responding B cells through the course of primary responses. MBC subsets that preferentially produce secondary GCs expressed comparatively higher BACH2 but lower BLIMP1 than those predisposed for PC development. Skewing the BLIMP1-BACH2 balance in otherwise fate-predisposed MBC subsets could switch their fate preferences. Underlying the changing BLIMP1-over-BACH2 balance, we observed progressively increased accessibilities at chromatin loci that are specifically opened in PCs, particularly those that contain interferon-sensitive response elements (ISREs) and are controlled by interferon regulatory factor 4 (IRF4). IRF4 is upregulated by B cell receptor, CD40 or innate receptor signaling and it induces graded levels of PC-specifying epigenetic imprints according to the strength of stimulation. By analyzing history-stamped GC B cells, we found progressively increased chromatin accessibilities at PC-specific, IRF4-controlled gene loci over time. Therefore, the cumulative stimulation history of B cells is epigenetically recorded in an IRF4-dependent manner, determines the relative strength between BLIMP1 and BACH2 in individual MBCs and dictates their probabilities to develop into GCs or PCs upon restimulation.
Assuntos
Fatores de Transcrição de Zíper de Leucina Básica , Diferenciação Celular , Epigênese Genética , Centro Germinativo , Memória Imunológica , Fatores Reguladores de Interferon , Células B de Memória , Plasmócitos , Fator 1 de Ligação ao Domínio I Regulador Positivo , Fator 1 de Ligação ao Domínio I Regulador Positivo/metabolismo , Fator 1 de Ligação ao Domínio I Regulador Positivo/genética , Animais , Fatores Reguladores de Interferon/metabolismo , Fatores Reguladores de Interferon/genética , Camundongos , Fatores de Transcrição de Zíper de Leucina Básica/metabolismo , Fatores de Transcrição de Zíper de Leucina Básica/genética , Células B de Memória/imunologia , Células B de Memória/metabolismo , Plasmócitos/imunologia , Plasmócitos/metabolismo , Centro Germinativo/imunologia , Centro Germinativo/metabolismo , Camundongos Endogâmicos C57BL , Transdução de Sinais , Ativação Linfocitária/genéticaRESUMO
Antibodies mediate natural and vaccine-induced immunity against viral and bacterial pathogens, whereas fungi represent a widespread kingdom of pathogenic species for which neither vaccine nor neutralizing antibody therapies are clinically available. Here, using a multi-kingdom antibody profiling (multiKAP) approach, we explore the human antibody repertoires against gut commensal fungi (mycobiota). We identify species preferentially targeted by systemic antibodies in humans, with Candida albicans being the major inducer of antifungal immunoglobulin G (IgG). Fungal colonization of the gut induces germinal center (GC)-dependent B cell expansion in extraintestinal lymphoid tissues and generates systemic antibodies that confer protection against disseminated C. albicans or C. auris infection. Antifungal IgG production depends on the innate immunity regulator CARD9 and CARD9+CX3CR1+ macrophages. In individuals with invasive candidiasis, loss-of-function mutations in CARD9 are associated with impaired antifungal IgG responses. These results reveal an important role of gut commensal fungi in shaping the human antibody repertoire through CARD9-dependent induction of host-protective antifungal IgG.
Assuntos
Anticorpos Antifúngicos/imunologia , Proteínas Adaptadoras de Sinalização CARD/metabolismo , Trato Gastrointestinal/imunologia , Trato Gastrointestinal/microbiologia , Imunidade , Imunoglobulina G/imunologia , Micobioma/imunologia , Animais , Linfócitos B/imunologia , Candida albicans/imunologia , Candidíase/imunologia , Candidíase/microbiologia , Fezes/microbiologia , Centro Germinativo/imunologia , Humanos , Camundongos Endogâmicos C57BL , Fagócitos/metabolismo , Polimorfismo de Nucleotídeo Único/genética , Ligação Proteica , Transdução de SinaisRESUMO
Regulatory T cells prevent the emergence of autoantibodies and excessive IgE, but the precise mechanisms are unclear. Here, we show that BCL6-expressing Tregs, known as follicular regulatory T (Tfr) cells, produce abundant neuritin protein that targets B cells. Mice lacking Tfr cells or neuritin in Foxp3-expressing cells accumulated early plasma cells in germinal centers (GCs) and developed autoantibodies against histones and tissue-specific self-antigens. Upon immunization, these mice also produced increased plasma IgE and IgG1. We show that neuritin is taken up by B cells, causes phosphorylation of numerous proteins, and dampens IgE class switching. Neuritin reduced differentiation of mouse and human GC B cells into plasma cells, downregulated BLIMP-1, and upregulated BCL6. Administration of neuritin to Tfr-deficient mice prevented the accumulation of early plasma cells in GCs. Production of neuritin by Tfr cells emerges as a central mechanism to suppress B cell-driven autoimmunity and IgE-mediated allergies.
Assuntos
Linfócitos B/imunologia , Proteínas do Tecido Nervoso/metabolismo , Linfócitos T Reguladores/imunologia , Animais , Autoanticorpos/imunologia , Autoimunidade , Linfócitos B/citologia , Linfócitos B/metabolismo , Diferenciação Celular , Fatores de Transcrição Forkhead/genética , Fatores de Transcrição Forkhead/metabolismo , Proteínas Ligadas por GPI/metabolismo , Centro Germinativo/imunologia , Centro Germinativo/metabolismo , Histonas/imunologia , Switching de Imunoglobulina , Imunoglobulina E/sangue , Imunoglobulina E/imunologia , Imunoglobulina G/sangue , Imunoglobulina G/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Fosforilação , Plasmócitos/citologia , Plasmócitos/imunologia , Plasmócitos/metabolismo , Fator 1 de Ligação ao Domínio I Regulador Positivo/genética , Fator 1 de Ligação ao Domínio I Regulador Positivo/metabolismo , Proteínas Proto-Oncogênicas c-bcl-6/genética , Proteínas Proto-Oncogênicas c-bcl-6/metabolismo , Linfócitos T Reguladores/citologia , Linfócitos T Reguladores/metabolismoRESUMO
Immunological memory is required for protection against repeated infections and is the basis of all effective vaccines. Antibodies produced by memory B cells play an essential role in many of these responses. We have combined lineage tracing with antibody cloning from single B cells to examine the role of affinity in B cell selection into germinal centers (GCs) and the memory B cell compartment in mice immunized with an HIV-1 antigen. We find that contemporaneously developing memory and GC B cells differ in their affinity for antigen throughout the immune response. Whereas GC cells and their precursors are enriched in antigen binding, memory B cells are not. Thus, the polyclonal memory B cell compartment is composed of B cells that were activated during the immune response but whose antigen binding affinity failed to support further clonal expansion in the GC.
Assuntos
Afinidade de Anticorpos/imunologia , Linfócitos B/imunologia , Centro Germinativo/imunologia , Memória Imunológica , Animais , Antígenos/metabolismo , Células HEK293 , Humanos , Imunização , Camundongos , Mutação/genética , Receptores de Antígenos de Linfócitos B/metabolismoRESUMO
Repeated exposure to pathogens or their antigens triggers anamnestic antibody responses that are higher in magnitude and affinity than the primary response. These involve reengagement of memory B cell (MBC) clones, the diversity and specificity of which determine the breadth and effectiveness of the ensuing antibody response. Using prime-boost models in mice, we find that secondary responses are characterized by a clonality bottleneck that restricts the engagement of the large diversity of MBC clones generated by priming. Rediversification of mutated MBCs is infrequent within secondary germinal centers (GCs), which instead consist predominantly of B cells without prior GC experience or detectable clonal expansion. Few MBC clones, generally derived from higher-affinity germline precursors, account for the majority of secondary antibody responses, while most primary-derived clonal diversity is not reengaged detectably by boosting. Understanding how to counter this bottleneck may improve our ability to elicit antibodies to non-immunodominant epitopes by vaccination.
Assuntos
Linfócitos B/imunologia , Centro Germinativo/imunologia , Memória Imunológica/imunologia , Imunidade Adaptativa/imunologia , Animais , Formação de Anticorpos/imunologia , Formação de Anticorpos/fisiologia , Antígenos/imunologia , Linfócitos B/metabolismo , Células CHO , Linhagem Celular , Cricetulus , Feminino , Centro Germinativo/metabolismo , Humanos , Memória Imunológica/fisiologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Modelos AnimaisRESUMO
Humoral responses in coronavirus disease 2019 (COVID-19) are often of limited durability, as seen with other human coronavirus epidemics. To address the underlying etiology, we examined post mortem thoracic lymph nodes and spleens in acute SARS-CoV-2 infection and observed the absence of germinal centers and a striking reduction in Bcl-6+ germinal center B cells but preservation of AID+ B cells. Absence of germinal centers correlated with an early specific block in Bcl-6+ TFH cell differentiation together with an increase in T-bet+ TH1 cells and aberrant extra-follicular TNF-α accumulation. Parallel peripheral blood studies revealed loss of transitional and follicular B cells in severe disease and accumulation of SARS-CoV-2-specific "disease-related" B cell populations. These data identify defective Bcl-6+ TFH cell generation and dysregulated humoral immune induction early in COVID-19 disease, providing a mechanistic explanation for the limited durability of antibody responses in coronavirus infections, and suggest that achieving herd immunity through natural infection may be difficult.
Assuntos
Infecções por Coronavirus/imunologia , Centro Germinativo/imunologia , Pneumonia Viral/imunologia , Linfócitos T Auxiliares-Indutores/imunologia , Idoso , Idoso de 80 Anos ou mais , Linfócitos B/imunologia , COVID-19 , Feminino , Centro Germinativo/patologia , Humanos , Masculino , Pessoa de Meia-Idade , Pandemias , Proteínas Proto-Oncogênicas c-bcl-6/genética , Proteínas Proto-Oncogênicas c-bcl-6/metabolismo , Baço/imunologia , Baço/patologia , Fator de Necrose Tumoral alfa/metabolismoRESUMO
The most aggressive B cell lymphomas frequently manifest extranodal distribution and carry somatic mutations in the poorly characterized gene TBL1XR1. Here, we show that TBL1XR1 mutations skew the humoral immune response toward generating abnormal immature memory B cells (MB), while impairing plasma cell differentiation. At the molecular level, TBL1XR1 mutants co-opt SMRT/HDAC3 repressor complexes toward binding the MB cell transcription factor (TF) BACH2 at the expense of the germinal center (GC) TF BCL6, leading to pre-memory transcriptional reprogramming and cell-fate bias. Upon antigen recall, TBL1XR1 mutant MB cells fail to differentiate into plasma cells and instead preferentially reenter new GC reactions, providing evidence for a cyclic reentry lymphomagenesis mechanism. Ultimately, TBL1XR1 alterations lead to a striking extranodal immunoblastic lymphoma phenotype that mimics the human disease. Both human and murine lymphomas feature expanded MB-like cell populations, consistent with a MB-cell origin and delineating an unforeseen pathway for malignant transformation of the immune system.
Assuntos
Memória Imunológica/fisiologia , Linfoma Difuso de Grandes Células B/patologia , Proteínas Nucleares/genética , Células Precursoras de Linfócitos B/imunologia , Receptores Citoplasmáticos e Nucleares/genética , Proteínas Repressoras/genética , Animais , Fatores de Transcrição de Zíper de Leucina Básica/genética , Fatores de Transcrição de Zíper de Leucina Básica/metabolismo , Cromatina/química , Cromatina/metabolismo , Centro Germinativo/citologia , Centro Germinativo/imunologia , Centro Germinativo/metabolismo , Histona Desacetilases/metabolismo , Humanos , Linfoma Difuso de Grandes Células B/imunologia , Linfoma Difuso de Grandes Células B/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Mutagênese Sítio-Dirigida , Proteínas Nucleares/química , Proteínas Nucleares/metabolismo , Correpressor 2 de Receptor Nuclear/química , Correpressor 2 de Receptor Nuclear/metabolismo , Células Precursoras de Linfócitos B/citologia , Células Precursoras de Linfócitos B/metabolismo , Ligação Proteica , Proteínas Proto-Oncogênicas c-bcl-6/antagonistas & inibidores , Proteínas Proto-Oncogênicas c-bcl-6/genética , Proteínas Proto-Oncogênicas c-bcl-6/metabolismo , Interferência de RNA , RNA Interferente Pequeno/metabolismo , Receptores Citoplasmáticos e Nucleares/química , Receptores Citoplasmáticos e Nucleares/metabolismo , Proteínas Repressoras/química , Proteínas Repressoras/metabolismo , Transcrição GênicaRESUMO
Enzymes of the TET family are methylcytosine dioxygenases that undergo frequent mutational or functional inactivation in human cancers. Recurrent loss-of-function mutations in TET proteins are frequent in human diffuse large B cell lymphoma (DLBCL). Here, we investigate the role of TET proteins in B cell homeostasis and development of B cell lymphomas with features of DLBCL. We show that deletion of Tet2 and Tet3 genes in mature B cells in mice perturbs B cell homeostasis and results in spontaneous development of germinal center (GC)-derived B cell lymphomas with increased G-quadruplexes and R-loops. At a genome-wide level, G-quadruplexes and R-loops were associated with increased DNA double-strand breaks (DSBs) at immunoglobulin switch regions. Deletion of the DNA methyltransferase DNMT1 in TET-deficient B cells prevented expansion of GC B cells, diminished the accumulation of G-quadruplexes and R-loops and delayed B lymphoma development, consistent with the opposing functions of DNMT and TET enzymes in DNA methylation and demethylation. Clustered regularly interspaced short palindromic repeats (CRISPR)-mediated depletion of nucleases and helicases that regulate G-quadruplexes and R-loops decreased the viability of TET-deficient B cells. Our studies suggest a molecular mechanism by which TET loss of function might predispose to the development of B cell malignancies.
Assuntos
Linfócitos B/imunologia , Carcinogênese/imunologia , Proteínas de Ligação a DNA/deficiência , Proteínas de Ligação a DNA/imunologia , Dioxigenases/imunologia , Homeostase/imunologia , Estruturas R-Loop/imunologia , Animais , Diferenciação Celular/imunologia , Metilação de DNA/imunologia , Quadruplex G , Centro Germinativo/imunologia , Camundongos , Camundongos Endogâmicos C57BLRESUMO
Ineffective antibody-mediated responses are a key characteristic of chronic viral infection. However, our understanding of the intrinsic mechanisms that drive this dysregulation are unclear. Here, we identify that targeting the epigenetic modifier BMI-1 in mice improves humoral responses to chronic lymphocytic choriomeningitis virus. BMI-1 was upregulated by germinal center B cells in chronic viral infection, correlating with changes to the accessible chromatin landscape, compared to acute infection. B cell-intrinsic deletion of Bmi1 accelerated viral clearance, reduced splenomegaly and restored splenic architecture. Deletion of Bmi1 restored c-Myc expression in B cells, concomitant with improved quality of antibody and coupled with reduced antibody-secreting cell numbers. Specifically, BMI-1-deficiency induced antibody with increased neutralizing capacity and enhanced antibody-dependent effector function. Using a small molecule inhibitor to murine BMI-1, we could deplete antibody-secreting cells and prohibit detrimental immune complex formation in vivo. This study defines BMI-1 as a crucial immune modifier that controls antibody-mediated responses in chronic infection.
Assuntos
Linfócitos B/imunologia , Imunidade Humoral/imunologia , Coriomeningite Linfocítica/imunologia , Vírus da Coriomeningite Linfocítica/imunologia , Complexo Repressor Polycomb 1/imunologia , Proteínas Proto-Oncogênicas/imunologia , Imunidade Adaptativa/imunologia , Animais , Anticorpos Neutralizantes/imunologia , Anticorpos Antivirais/imunologia , Formação de Anticorpos/imunologia , Feminino , Centro Germinativo/imunologia , Masculino , Camundongos , Camundongos Endogâmicos C57BLRESUMO
Germinal centers (GCs) were described more than 125 years ago as compartments within secondary lymphoid organs that contained mitotic cells. Since then, it has become clear that this structure is the site of B cell clonal expansion, somatic hypermutation, and affinity-based selection, the combination of which results in the production of high-affinity antibodies. Decades of anatomical and functional studies have led to an overall model of how the GC reaction and affinity-based selection operate. More recently, the introduction of intravital imaging into the GC field has opened the door to direct investigation of certain key dynamic features of this microanatomic structure, sparking renewed interest in the relationship between cell movement and affinity maturation. We review these and other recent advances in our understanding of GCs, focusing on cellular dynamics and on the mechanism of selection of high-affinity B cells.