RESUMO
Diversity is the cornerstone of the adaptive immune system, crucial for its effectiveness against constantly evolving pathogens that pose threats to higher vertebrates. Accurately measuring and interpreting this diversity presents challenges for immunologists, as changes in diversity and clonotype composition can tip the balance between protective immunity and autoimmunity. In this review, we present the current methods commonly used to measure diversity from single-cell T-cell receptor and B-cell receptor sequencing. We also discuss two case studies where single-cell sequencing and diversity estimations have led to breakthroughs in autoimmune disease discovery and therapeutic innovation, and reflect upon the necessity and importance of accurately defining and measuring lymphocyte diversity in these contexts.
RESUMO
Whole-exome sequencing of two unrelated kindreds with systemic autoimmune disease featuring antinuclear antibodies with IgG4 elevation uncovered an identical ultrarare heterozygous TNIP1Q333P variant segregating with disease. Mice with the orthologous Q346P variant developed antinuclear autoantibodies, salivary gland inflammation, elevated IgG2c, spontaneous germinal centers and expansion of age-associated B cells, plasma cells and follicular and extrafollicular helper T cells. B cell phenotypes were cell-autonomous and rescued by ablation of Toll-like receptor 7 (TLR7) or MyD88. The variant increased interferon-ß without altering nuclear factor kappa-light-chain-enhancer of activated B cells signaling, and impaired MyD88 and IRAK1 recruitment to autophagosomes. Additionally, the Q333P variant impaired TNIP1 localization to damaged mitochondria and mitophagosome formation. Damaged mitochondria were abundant in the salivary epithelial cells of Tnip1Q346P mice. These findings suggest that TNIP1-mediated autoimmunity may be a consequence of increased TLR7 signaling due to impaired recruitment of downstream signaling molecules and damaged mitochondria to autophagosomes and may thus respond to TLR7-targeted therapeutics.
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CD11c+ atypical B cells (ABCs) are an alternative memory B cell lineage associated with immunization, infection, and autoimmunity. However, the factors that drive the transcriptional program of ABCs have not been identified, and the function of this population remains incompletely understood. Here, we identified candidate transcription factors associated with the ABC population based on a human tonsillar B cell single-cell dataset. We identified CD11c+ B cells in mice with a similar transcriptomic signature to human ABCs, and using an optimized CRISPR-Cas9 knockdown screen, we observed that loss of zinc finger E-box binding homeobox 2 (Zeb2) impaired ABC formation. Furthermore, ZEB2 haplo-insufficient Mowat-Wilson syndrome (MWS) patients have decreased circulating ABCs in the blood. In Cd23Cre/+Zeb2fl/fl mice with impaired ABC formation, ABCs were dispensable for efficient humoral responses after Plasmodium sporozoite immunization but were required to control recrudescent blood-stage malaria. Immune phenotyping revealed that ABCs drive optimal T follicular helper (TFH) cell formation and germinal center (GC) responses and they reside at the red/white pulp border, likely permitting better access to pathogen antigens for presentation. Collectively, our study shows that ABC formation is dependent on Zeb2, and these cells can limit recrudescent infection by sustaining GC reactions.
Assuntos
Centro Germinativo , Infecção Persistente , Animais , Humanos , Camundongos , Imunização , Vacinação , Homeobox 2 de Ligação a E-box com Dedos de Zinco/genéticaRESUMO
In antibody responses, mutated germinal center B (BGC) cells are positively selected for reentry or differentiation. As the products from GCs, memory B cells and antibody-secreting cells (ASCs) support high-affinity and long-lasting immunity. Positive selection of BGC cells is controlled by signals received through the B cell receptor (BCR) and follicular helper T (TFH) cell-derived signals, in particular costimulation through CD40. Here, we demonstrate that the TFH cell effector cytokine interleukin-21 (IL-21) joins BCR and CD40 in supporting BGC selection and reveal that strong IL-21 signaling prioritizes ASC differentiation in vivo. BGC cells, compared with non-BGC cells, show significantly reduced IL-21 binding and attenuated signaling, which is mediated by low cellular heparan sulfate (HS) sulfation. Mechanistically, N-deacetylase and N-sulfotransferase 1 (Ndst1)-mediated N-sulfation of HS in B cells promotes IL-21 binding and signal strength. Ndst1 is down-regulated in BGC cells and up-regulated in ASC precursors, suggesting selective desensitization to IL-21 in BGC cells. Thus, specialized biochemical regulation of IL-21 bioavailability and signal strength sets a balance between the stringency and efficiency of GC selection.
Assuntos
Centro Germinativo , Linfócitos T Auxiliares-Indutores , Disponibilidade Biológica , Diferenciação Celular , Receptores de Antígenos de Linfócitos B/metabolismo , Antígenos CD40RESUMO
During infections with protozoan parasites or some viruses, T cell immunosuppression is generated simultaneously with a high B cell activation. It has been described that, as well as producing antibodies, plasmablasts, the differentiation product of activated B cells, can condition the development of protective immunity in infections. Here, we show that, in T. cruzi infection, all the plasmablasts detected during the acute phase of the infection had higher surface expression of PD-L1 than other mononuclear cells. PD-L1hi plasmablasts were induced in vivo in a BCR-specific manner and required help from Bcl-6+CD4+T cells. PD-L1hi expression was not a characteristic of all antibody-secreting cells since plasma cells found during the chronic phase of infection expressed PD-L1 but at lower levels. PD-L1hi plasmablasts were also present in mice infected with Plasmodium or with lymphocytic choriomeningitis virus, but not in mice with autoimmune disorders or immunized with T cell-dependent antigens. In vitro experiments showed that PD-L1hi plasmablasts suppressed the T cell response, partially via PD-L1. Thus, this study reveals that extrafollicular PD-L1hi plasmablasts, whose peaks of response precede the peak of germinal center response, may have a modulatory function in infections, thus influencing T cell response.
Assuntos
Antígeno B7-H1 , Linfócitos T , Animais , Linfócitos B , Ativação Linfocitária , Camundongos , PlasmócitosRESUMO
Although circumstantial evidence supports enhanced Toll-like receptor 7 (TLR7) signalling as a mechanism of human systemic autoimmune disease1-7, evidence of lupus-causing TLR7 gene variants is lacking. Here we describe human systemic lupus erythematosus caused by a TLR7 gain-of-function variant. TLR7 is a sensor of viral RNA8,9 and binds to guanosine10-12. We identified a de novo, previously undescribed missense TLR7Y264H variant in a child with severe lupus and additional variants in other patients with lupus. The TLR7Y264H variant selectively increased sensing of guanosine and 2',3'-cGMP10-12, and was sufficient to cause lupus when introduced into mice. We show that enhanced TLR7 signalling drives aberrant survival of B cell receptor (BCR)-activated B cells, and in a cell-intrinsic manner, accumulation of CD11c+ age-associated B cells and germinal centre B cells. Follicular and extrafollicular helper T cells were also increased but these phenotypes were cell-extrinsic. Deficiency of MyD88 (an adaptor protein downstream of TLR7) rescued autoimmunity, aberrant B cell survival, and all cellular and serological phenotypes. Despite prominent spontaneous germinal-centre formation in Tlr7Y264H mice, autoimmunity was not ameliorated by germinal-centre deficiency, suggesting an extrafollicular origin of pathogenic B cells. We establish the importance of TLR7 and guanosine-containing self-ligands for human lupus pathogenesis, which paves the way for therapeutic TLR7 or MyD88 inhibition.
Assuntos
Mutação com Ganho de Função , Lúpus Eritematoso Sistêmico , Receptor 7 Toll-Like , Animais , Autoimunidade/genética , Linfócitos B , GMP Cíclico/análogos & derivados , Guanosina , Humanos , Lúpus Eritematoso Sistêmico/genética , Camundongos , Fator 88 de Diferenciação Mieloide/genética , Fator 88 de Diferenciação Mieloide/metabolismo , Receptor 7 Toll-Like/genética , Receptor 7 Toll-Like/metabolismoRESUMO
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
Class-switch recombination (CSR) is a DNA recombination process that replaces the immunoglobulin (Ig) constant region for the isotype that can best protect against the pathogen. Dysregulation of CSR can cause self-reactive BCRs and B cell lymphomas; understanding the timing and location of CSR is therefore important. Although CSR commences upon T cell priming, it is generally considered a hallmark of germinal centers (GCs). Here, we have used multiple approaches to show that CSR is triggered prior to differentiation into GC B cells or plasmablasts and is greatly diminished in GCs. Despite finding a small percentage of GC B cells expressing germline transcripts, phylogenetic trees of GC BCRs from secondary lymphoid organs revealed that the vast majority of CSR events occurred prior to the onset of somatic hypermutation. As such, we have demonstrated the existence of IgM-dominated GCs, which are unlikely to occur under the assumption of ongoing switching.
Assuntos
Linfócitos B/imunologia , Centro Germinativo/imunologia , Switching de Imunoglobulina , Plasmócitos/imunologia , Linfoma Plasmablástico/imunologia , Linfócitos T Auxiliares-Indutores/imunologia , Animais , Diferenciação Celular , Células Cultivadas , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Filogenia , Receptores de Antígenos de Linfócitos B/metabolismoRESUMO
Mucosal lymphoid tissues such as human tonsil are colonized by bacteria and exposed to ingested and inhaled antigens, requiring tight regulation of immune responses. Antibody responses are regulated by follicular helper T (TFH) cells and FOXP3+ follicular regulatory T (TFR) cells. Here we describe a subset of human tonsillar follicular T cells identified by expression of TFH markers and CD25 that are the main source of follicular T (TF) cell-derived IL-10. Despite lack of FOXP3 expression, CD25+ TF cells resemble T reg cells in high CTLA4 expression, low IL-2 production, and their ability to repress T cell proliferation. CD25+ TF cell-derived IL-10 dampens induction of B cell class-switching to IgE. In children, circulating total IgE titers were inversely correlated with the frequencies of tonsil CD25+ TF cells and IL-10-producing TF cells but not with total T reg cells, TFR, or IL-10-producing T cells. Thus, CD25+ TF cells emerge as a subset with unique T and B cell regulatory activities that may help prevent atopy.
Assuntos
Interleucina-10/metabolismo , Linfócitos T Auxiliares-Indutores/imunologia , Linfócitos T Reguladores/imunologia , Linfócitos B/imunologia , Antígeno CTLA-4/metabolismo , Proliferação de Células , Células Cultivadas , Criança , Fatores de Transcrição Forkhead/metabolismo , Humanos , Switching de Imunoglobulina/imunologia , Imunoglobulina E/sangue , Subunidade alfa de Receptor de Interleucina-2/metabolismo , Linfonodos/imunologia , Linfonodos/patologia , Ativação Linfocitária , Mesentério , Tonsila Palatina/imunologia , Tonsila Palatina/patologiaRESUMO
Systemic lupus erythematosus (SLE) is the prototypic systemic autoimmune disease. It is thought that many common variant gene loci of weak effect act additively to predispose to common autoimmune diseases, while the contribution of rare variants remains unclear. Here we describe that rare coding variants in lupus-risk genes are present in most SLE patients and healthy controls. We demonstrate the functional consequences of rare and low frequency missense variants in the interacting proteins BLK and BANK1, which are present alone, or in combination, in a substantial proportion of lupus patients. The rare variants found in patients, but not those found exclusively in controls, impair suppression of IRF5 and type-I IFN in human B cell lines and increase pathogenic lymphocytes in lupus-prone mice. Thus, rare gene variants are common in SLE and likely contribute to genetic risk.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/genética , Predisposição Genética para Doença , Lúpus Eritematoso Sistêmico/genética , Proteínas de Membrana/genética , Quinases da Família src/genética , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Adolescente , Adulto , Animais , Linfócitos B/citologia , Linfócitos B/imunologia , Linfócitos B/metabolismo , Estudos de Casos e Controles , Linhagem Celular , Núcleo Celular/imunologia , Núcleo Celular/metabolismo , Criança , Modelos Animais de Doenças , Feminino , Frequência do Gene , Células HEK293 , Voluntários Saudáveis , Humanos , Fatores Reguladores de Interferon/imunologia , Fatores Reguladores de Interferon/metabolismo , Interferon Tipo I/imunologia , Interferon Tipo I/metabolismo , Lúpus Eritematoso Sistêmico/sangue , Lúpus Eritematoso Sistêmico/imunologia , Masculino , Proteínas de Membrana/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Mutação de Sentido Incorreto , Sequenciamento do Exoma , Quinases da Família src/metabolismoRESUMO
DNA vaccination is an attractive approach to elicit tumor-specific cytotoxic CD8+ T lymphocytes (CTL), which can mediate protective immunity against tumors. To initiate CTL responses, antigen-encoding plasmids employed for DNA vaccination need to activate dendritic cells (DC) through the stimulation of DNA-sensing innate immune receptors that converge in the activation of the master transcription factor NF-κB. To this end, NF-κB repressor IκBα needs to be degraded, allowing NF-κB to translocate to the nucleus and transcribe proinflammatory target genes, as well as its repressor IκBα. Therefore, NF-κB activation is self-limited by de novo synthesis of IκBa, which sequesters NF-κB in the cytosol. Hence, we tested whether co-delivering a shRNA-based adjuvant able to silence IκBα expression would further promote DNA-induced NFκB activation, DC activation and tumor-protective CTL responses induced by DNA vaccination in a preclinical model. First, an IκBα-targeting shRNA plasmid (shIκBα) was shown to reduce IκBα expression and promote NFκB-driven transcription in vitro, as well as up-regulate inflammatory target genes in vivo. Then, we showed that intradermal DNA electroporation induced the migration of skin migratory dendritic cells to draining lymph nodes and maturation of dermal dendritic cells (dDC). Interestingly, shIκBα further promoted the migration of mature skin migratory dendritic cells, in particular dDC, which are specialized in antigen cross-presentation and activation of CD8+ T cells. Consistently, mice vaccinated with a plasmid encoding the melanoma-associated antigen tyrosinase-related protein 2 (TRP2) in combination with shIκBα enhanced TRP2-specific CTL responses and reduced the number of lung melanoma foci in mice challenged with intravenous injection of B16F10 cells. Moreover, therapeutic vaccination with pTRP2 and shIκBα delayed the growth of B16F10 melanoma subcutaneous tumors. Our data suggest that adjuvants promoting NF-κB activation represent an attractive strategy to boost DC activation and promote the generation of tumor-protective CTL responses elicited by DNA vaccines.
Assuntos
Vacinas Anticâncer/imunologia , Células de Langerhans/imunologia , Linfonodos/imunologia , Inibidor de NF-kappaB alfa/antagonistas & inibidores , RNA Interferente Pequeno/metabolismo , Linfócitos T Citotóxicos/imunologia , Vacinas de DNA/imunologia , Adjuvantes Imunológicos/metabolismo , Animais , Vacinas Anticâncer/administração & dosagem , Movimento Celular , Modelos Animais de Doenças , Células de Langerhans/fisiologia , Pulmão/patologia , Melanoma/patologia , Melanoma/terapia , Camundongos Endogâmicos C57BL , Resultado do Tratamento , Vacinação , Vacinas de DNA/administração & dosagemRESUMO
Current HIV vaccines are poor inducers of neutralizing antibodies (nAbs). A recent study in Cell Reports used serial fine-needle aspirates from rhesus macaque lymph nodes following HIV-1 surface envelope glycoprotein (Env) trimer immunization, generating a substantial production of HIV-1 nAbs. A remarkable correlation was found between antibody titers and a high frequency and ratio of germinal center B and T follicular helper (TFH) lymphocytes.
Assuntos
Vacinas contra a AIDS/imunologia , Anticorpos Neutralizantes/imunologia , Centro Germinativo/imunologia , Anticorpos Anti-HIV/imunologia , Infecções por HIV/prevenção & controle , HIV-1/imunologia , Produtos do Gene env do Vírus da Imunodeficiência Humana/imunologia , Vacinas contra a AIDS/uso terapêutico , Animais , Centro Germinativo/virologia , Infecções por HIV/imunologia , Infecções por HIV/virologia , Humanos , Linfócitos/imunologia , Linfócitos/virologia , Macaca mulatta , Produtos do Gene env do Vírus da Imunodeficiência Humana/uso terapêuticoRESUMO
DNA vaccines have emerged as an attractive strategy to promote protective cellular and humoral immunity against the encoded antigen. DNA vaccines are easy to generate, inexpensive to produce and purify at large-scale, highly stable and safe. In addition, plasmids used for DNA vaccines act as powerful "danger signals" by stimulating several DNA-sensing innate immune receptors that promote the induction of protective adaptive immunity. The induction of tumor-specific immune responses represents a major challenge for DNA vaccines because most of tumor-associated antigens are normal non-mutated self-antigens. As a consequence, induction of potentially self-reactive T cell responses against such poorly immunogenic antigens is controlled by mechanisms of central and peripheral tolerance as well as tumor-induced immunosuppression. Although several DNA vaccines against cancer have reached clinical testing, disappointing results have been observed. Therefore, the development of new adjuvants that strongly stimulate the induction of antitumor T cell immunity and counteract immune-suppressive regulation is an attractive approach to enhance the potency of DNA vaccines and overcome tumor-associated tolerance. Understanding the DNA-sensing signaling pathways of innate immunity that mediate the induction of T cell responses elicited by DNA vaccines represents a unique opportunity to develop novel adjuvants that enhance vaccine potency. The advance of DNA adjuvants needs to be complemented with the development of potent delivery systems, in order to step toward successful clinical application. Here, we briefly discuss recent evidence showing how to harness DNA-induced immune response to improve the potency of cancer vaccines and counteract tumor-associated tolerance.