RESUMEN
The cytokine interleukin-21 (IL-21) is a pivotal T cell-derived signal crucial for germinal center (GC) responses, but the precise mechanisms by which IL-21 influences B cell function remain elusive. Here, we investigated the B cell-intrinsic role of IL-21 signaling by employing a novel IL-21 receptor ( Il21r ) conditional knock-out mouse model and ex vivo culture systems and uncovered a surprising duality of IL-21 signaling in B cells. While IL-21 stimulation of naïve B cells led to Bim-dependent apoptosis, it promoted robust proliferation of pre-activated B cells, particularly class-switched IgG1 + B cells ex vivo . Consistent with this, B cell-specific deletion of Il21r led to a severe defect in IgG1 responses in vivo following immunization. Intriguingly, Il21r -deleted B cells are significantly impaired in their ability to transition from a pre-GC to a GC state following immunization. Although Il21r -deficiency did not affect the proportion of IgG1 + B cells among GC B cells, it greatly diminished the proportion of IgG1 + B cells among the plasmablast/plasma cell population. Collectively, our data suggest that IL-21 serves as a critical regulator of B cell fates, influencing B cell apoptosis and proliferation in a context-dependent manner.
RESUMEN
BACKGROUND: Swi6 acts as a transcription factor in budding yeast, functioning in two different heterodimeric complexes, SBF and MBF, that activate the expression of distinct but overlapping sets of genes. Swi6 undergoes regulated changes in nucleocytoplasmic localization throughout the cell cycle that correlate with changes in gene expression. This study investigates how nucleocytoplasmic transport by multiple transport factors may influence specific Swi6 activities. RESULTS: Here we show that the exportin Crm1 is important for Swi6 nuclear export and activity. Loss of a putative Crm1 NES or inhibition of Crm1 activity results in changes in nucleocytoplasmic Swi6 localization. Alteration of the Crm1 NES in Swi6 results in decreased MBF-mediated gene expression, but does not affect SBF reporter expression, suggesting that export of Swi6 by Crm1 regulates a subset of Swi6 transcription activation activity. Finally, alteration of the putative Crm1 NES in Swi6 results in cells that are larger than wild type, and this increase in cell size is exacerbated by deletion of Msn5. CONCLUSIONS: These data provide evidence that Swi6 has at least two different exportins, Crm1 and Msn5, each of which interacts with a distinct nuclear export signal. We identify a putative nuclear export signal for Crm1 within Swi6, and observe that export by Crm1 or Msn5 independently influences Swi6-regulated expression of a different subset of Swi6-controlled genes. These findings provide new insights into the complex regulation of Swi6 transcription activation activity and the role of nucleocytoplasmic shuttling in regulated gene expression.
Asunto(s)
Carioferinas , Proteínas de Saccharomyces cerevisiae , Transporte Activo de Núcleo Celular , Núcleo Celular/metabolismo , Carioferinas/genética , Carioferinas/metabolismo , Receptores Citoplasmáticos y Nucleares , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Activación Transcripcional , Proteína Exportina 1RESUMEN
Following infection or immunization, memory B cells (MBCs) and long-lived plasma cells provide humoral immunity that can last for decades. Most principles of MBC biology have been determined with hapten-protein carrier models or fluorescent protein immunizations. Here, we examine the temporal dynamics of the germinal center (GC) B cell and MBC response following mouse influenza A virus infection. We find that antiviral B cell responses within the lung-draining mediastinal lymph node (mLN) and the spleen are distinct in regard to duration, enrichment for antigen-binding cells, and class switching dynamics. While splenic GCs dissolve after 6 weeks post-infection, mLN hemagglutinin-specific (HA+) GCs can persist for 22 weeks. Persistent GCs continuously differentiate MBCs, with "peak" and "late" GCs contributing equal numbers of HA+ MBCs to the long-lived compartment. Our findings highlight critical aspects of persistent GC responses and MBC differentiation following respiratory virus infection with direct implications for developing effective vaccination strategies.
Asunto(s)
Anticuerpos Antivirales/inmunología , Centro Germinal/inmunología , Memoria Inmunológica , Virus de la Influenza A/fisiología , Células B de Memoria/inmunología , Infecciones por Orthomyxoviridae/inmunología , Proteínas de Dominio T Box/fisiología , Animales , Diferenciación Celular , Femenino , Activación de Linfocitos , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Infecciones por Orthomyxoviridae/patología , Infecciones por Orthomyxoviridae/virologíaRESUMEN
B cell responses are critical for antiviral immunity. However, a comprehensive picture of antigen-specific B cell differentiation, clonal proliferation, and dynamics in different organs after infection is lacking. Here, by combining single-cell RNA and B cell receptor (BCR) sequencing of antigen-specific cells in lymph nodes, spleen, and lungs after influenza infection in mice, we identify several germinal center (GC) B cell subpopulations and organ-specific differences that persist over the course of the response. We discover transcriptional differences between memory cells in lungs and lymphoid organs and organ-restricted clonal expansion. Remarkably, we find significant clonal overlap between GC-derived memory and plasma cells. By combining BCR-mutational analyses with monoclonal antibody (mAb) expression and affinity measurements, we find that memory B cells are highly diverse and can be selected from both low- and high-affinity precursors. By linking antigen recognition with transcriptional programming, clonal proliferation, and differentiation, these finding provide important advances in our understanding of antiviral immunity.
Asunto(s)
Antígenos Virales/inmunología , Linfocitos B/inmunología , Perfilación de la Expresión Génica , Gripe Humana/genética , Gripe Humana/inmunología , Receptores de Antígenos de Linfocitos B/metabolismo , Análisis de la Célula Individual , Animales , Anticuerpos Monoclonales/metabolismo , Diferenciación Celular/genética , Proliferación Celular , Células Clonales , Centro Germinal/inmunología , Glicoproteínas Hemaglutininas del Virus de la Influenza/inmunología , Humanos , Células B de Memoria/metabolismo , Ratones Endogámicos C57BL , Mutación/genética , Tasa de Mutación , Especificidad de Órganos , Células Plasmáticas/metabolismo , ARN/metabolismo , Transcripción GenéticaRESUMEN
Effective antiviral immunity requires generation of T and B lymphocytes expressing the transcription factor T-bet, a regulator of type 1 inflammatory responses. Using T-bet expression as an endogenous marker for cells participating in a type 1 response, we report coordinated interactions of T-bet-expressing T and B lymphocytes on the basis of their dynamic colocalization at the T cell zone and B follicle boundary (T-B boundary) and germinal centers (GCs) during lung influenza infection. We demonstrate that the assembly of this circuit takes place in distinct anatomical niches within the draining lymph node, guided by CXCR3 that enables positioning of TH1 cells at the T-B boundary. The encounter of B and TH1 cells at the T-B boundary enables IFN-γ produced by the latter to induce IgG2c class switching. Within GCs, T-bet+ TFH cells represent a specialized stable sublineage required for GC growth but dispensable for IgG2c class switching. Our studies show that during respiratory viral infection, T-bet-expressing T and B lymphocytes form a circuit assembled in a spatiotemporally controlled manner that acts as a functional unit enabling a robust and coherent humoral response tailored for optimal antiviral immunity.
Asunto(s)
Linfocitos B/inmunología , Inmunidad Humoral , Gripe Humana/inmunología , Subgrupos de Linfocitos T/inmunología , Células TH1/inmunología , Animales , Linfocitos B/metabolismo , Comunicación Celular/inmunología , Modelos Animales de Enfermedad , Femenino , Centro Germinal/citología , Centro Germinal/metabolismo , Humanos , Cambio de Clase de Inmunoglobulina , Virus de la Influenza A/inmunología , Gripe Humana/patología , Gripe Humana/virología , Interferón gamma/genética , Interferón gamma/metabolismo , Pulmón/inmunología , Pulmón/patología , Pulmón/virología , Masculino , Ratones , Ratones Transgénicos , Nippostrongylus/inmunología , Ratas , Receptores CXCR3/metabolismo , Infecciones por Strongylida/inmunología , Infecciones por Strongylida/parasitología , Proteínas de Dominio T Box/genética , Proteínas de Dominio T Box/metabolismo , Subgrupos de Linfocitos T/metabolismo , Células TH1/metabolismoRESUMEN
Precise targeting of activation-induced cytidine deaminase (AID) to immunoglobulin (Ig) loci promotes antibody class switch recombination (CSR) and somatic hypermutation (SHM), whereas AID targeting of non-Ig loci can generate oncogenic DNA lesions. Here, we examined the contribution of G-quadruplex (G4) nucleic acid structures to AID targeting in vivo. Mice bearing a mutation in Aicda (AIDG133V) that disrupts AID-G4 binding modeled the pathology of hyper-IgM syndrome patients with an orthologous mutation, lacked CSR and SHM, and had broad defects in genome-wide AIDG133V chromatin localization. Genome-wide analyses also revealed that wild-type AID localized to MHCII genes, and AID expression correlated with decreased MHCII expression in germinal center B cells and diffuse large B cell lymphoma. Our findings indicate a crucial role for G4 binding in AID targeting and suggest that AID activity may extend beyond Ig loci to regulate the expression of genes relevant to the physiology and pathology of activated B cells.
Asunto(s)
Cromatina/genética , Cromatina/metabolismo , Citidina Desaminasa/genética , Citidina Desaminasa/metabolismo , G-Cuádruplex , Síndrome de Inmunodeficiencia con Hiper-IgM/etiología , Síndrome de Inmunodeficiencia con Hiper-IgM/metabolismo , Mutación , Animales , Linfocitos B/inmunología , Linfocitos B/metabolismo , Biología Computacional/métodos , Modelos Animales de Enfermedad , Susceptibilidad a Enfermedades , Activación Enzimática , Técnica del Anticuerpo Fluorescente , Perfilación de la Expresión Génica , Estudio de Asociación del Genoma Completo , Centro Germinal/inmunología , Centro Germinal/metabolismo , Antígenos HLA/genética , Antígenos HLA/inmunología , Humanos , Síndrome de Inmunodeficiencia con Hiper-IgM/diagnóstico , Cambio de Clase de Inmunoglobulina/genética , Cambio de Clase de Inmunoglobulina/inmunología , Inmunofenotipificación , Activación de Linfocitos/genética , Linfoma de Células B Grandes Difuso/etiología , Linfoma de Células B Grandes Difuso/metabolismo , Linfoma de Células B Grandes Difuso/patología , Ratones , Ratones TransgénicosRESUMEN
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.
Asunto(s)
Memoria Inmunológica/fisiología , Linfoma de Células B Grandes Difuso/patología , Proteínas Nucleares/genética , Células Precursoras de Linfocitos B/inmunología , Receptores Citoplasmáticos y Nucleares/genética , Proteínas Represoras/genética , Animales , Factores de Transcripción con Cremalleras de Leucina de Carácter Básico/genética , Factores de Transcripción con Cremalleras de Leucina de Carácter Básico/metabolismo , Cromatina/química , Cromatina/metabolismo , Centro Germinal/citología , Centro Germinal/inmunología , Centro Germinal/metabolismo , Histona Desacetilasas/metabolismo , Humanos , Linfoma de Células B Grandes Difuso/inmunología , Linfoma de Células B Grandes Difuso/metabolismo , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Mutagénesis Sitio-Dirigida , Proteínas Nucleares/química , Proteínas Nucleares/metabolismo , Co-Represor 2 de Receptor Nuclear/química , Co-Represor 2 de Receptor Nuclear/metabolismo , Células Precursoras de Linfocitos B/citología , Células Precursoras de Linfocitos B/metabolismo , Unión Proteica , Proteínas Proto-Oncogénicas c-bcl-6/antagonistas & inhibidores , Proteínas Proto-Oncogénicas c-bcl-6/genética , Proteínas Proto-Oncogénicas c-bcl-6/metabolismo , Interferencia de ARN , ARN Interferente Pequeño/metabolismo , Receptores Citoplasmáticos y Nucleares/química , Receptores Citoplasmáticos y Nucleares/metabolismo , Proteínas Represoras/química , Proteínas Represoras/metabolismo , Transcripción GenéticaRESUMEN
A major obstacle to vaccination against antigenically variable viruses is skewing of antibody responses to variable immunodominant epitopes. For influenza virus hemagglutinin (HA), the immunodominance of the variable head impairs responses to the highly conserved stem. Here, we show that head immunodominance depends on the physical attachment of head to stem. Stem immunogenicity is enhanced by immunizing with stem-only constructs or by increasing local HA concentration in the draining lymph node. Surprisingly, coimmunization of full-length HA and stem alters stem-antibody class switching. Our findings delineate strategies for overcoming immunodominance, with important implications for human vaccination.
Asunto(s)
Anticuerpos Neutralizantes/inmunología , Epítopos/inmunología , Hemaglutininas/inmunología , Epítopos Inmunodominantes/inmunología , Virus de la Influenza A/inmunología , Vacunas contra la Influenza/inmunología , Animales , Anticuerpos Antivirales/inmunología , Linfocitos B/inmunología , Femenino , Ratones , Ratones Endogámicos C57BL , Infecciones por Orthomyxoviridae/inmunología , Infecciones por Orthomyxoviridae/prevención & control , Células Madre/inmunologíaRESUMEN
The immunoglobulin heavy chain (Igh) locus features a dynamic chromatin landscape to promote class switch recombination (CSR), yet the mechanisms that regulate this landscape remain poorly understood. CHD4, a component of the chromatin remodeling NuRD complex, directly binds H3K9me3, an epigenetic mark present at the Igh locus during CSR. We find that CHD4 is essential for early B cell development but is dispensable for the homeostatic maintenance of mature, naive B cells. However, loss of CHD4 in mature B cells impairs CSR because of suboptimal targeting of AID to the Igh locus. Additionally, we find that CHD4 represses p53 expression to promote B cell proliferation. This work reveals distinct roles for CHD4 in B cell development and CSR and links the H3K9me3 epigenetic mark with AID recruitment to the Igh locus.
Asunto(s)
Linfocitos B/inmunología , Proliferación Celular , ADN Helicasas/genética , Cambio de Clase de Inmunoglobulina , Animales , Linfocitos B/citología , Linfocitos B/fisiología , Diferenciación Celular , Células Cultivadas , Ensamble y Desensamble de Cromatina , ADN Helicasas/metabolismo , Genes de las Cadenas Pesadas de las Inmunoglobulinas , Ratones , Proteína p53 Supresora de Tumor/genética , Proteína p53 Supresora de Tumor/metabolismoRESUMEN
The DNA damage response protein ATM has long been known to influence class switch recombination in ex vivo-cultured B cells. However, an assessment of B cell-intrinsic requirement of ATM in humoral responses in vivo was confounded by the fact that its germline deletion affects T cell function, and B:T cell interactions are critical for in vivo immune responses. In this study, we demonstrate that B cell-specific deletion of ATM in mice leads to reduction in germinal center (GC) frequency and size in response to immunization. We find that loss of ATM induces apoptosis of GC B cells, likely due to unresolved DNA lesions in cells attempting to undergo class-switch recombination. Accordingly, suboptimal GC responses in ATM-deficient animals are characterized by decreased titers of class-switched Abs and decreased rates of somatic hypermutation. These results unmask the critical B cell-intrinsic role of ATM in maintaining an optimal GC response following immunization.
Asunto(s)
Proteínas de la Ataxia Telangiectasia Mutada/metabolismo , Linfocitos B/fisiología , Centro Germinal/fisiología , Linfocitos T/fisiología , Animales , Proteínas de la Ataxia Telangiectasia Mutada/genética , Células Cultivadas , Reparación del ADN/genética , Cambio de Clase de Inmunoglobulina , Ratones , Ratones Noqueados , Receptores de Complemento 3d/genética , Hipermutación Somática de InmunoglobulinaRESUMEN
The modulator of retrovirus infection (MRI or CYREN) is a 30-kDa protein with a conserved N-terminal Ku-binding motif (KBM) and a C-terminal XLF-like motif (XLM). We show that MRI is intrinsically disordered and interacts with many DNA damage response (DDR) proteins, including the kinases ataxia telangiectasia mutated (ATM) and DNA-PKcs and the classical non-homologous end joining (cNHEJ) factors Ku70, Ku80, XRCC4, XLF, PAXX, and XRCC4. MRI forms large multimeric complexes that depend on its N and C termini and localizes to DNA double-strand breaks (DSBs), where it promotes the retention of DDR factors. Mice deficient in MRI and XLF exhibit embryonic lethality at a stage similar to those deficient in the core cNHEJ factors XRCC4 or DNA ligase IV. Moreover, MRI is required for cNHEJ-mediated DSB repair in XLF-deficient lymphocytes. We propose that MRI is an adaptor that, through multivalent interactions, increases the avidity of DDR factors to DSB-associated chromatin to promote cNHEJ.
Asunto(s)
Roturas del ADN de Doble Cadena , Reparación del ADN por Unión de Extremidades , Animales , Proteínas de Ciclo Celular/metabolismo , Cromatina/genética , Cromatina/metabolismo , ADN Ligasa (ATP)/genética , Reparación del ADN , Enzimas Reparadoras del ADN/genética , Enzimas Reparadoras del ADN/metabolismo , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Humanos , Autoantígeno Ku/genética , RatonesRESUMEN
Heterochromatin formed by the SUV39 histone methyltransferases represses transcription from repetitive DNA sequences and ensures genomic stability. How SUV39 enzymes localize to their target genomic loci remains unclear. Here, we demonstrate that chromatin-associated RNA contributes to the stable association of SUV39H1 with constitutive heterochromatin in human cells. We find that RNA associated with mitotic chromosomes is concentrated at pericentric heterochromatin, and is encoded, in part, by repetitive α-satellite sequences, which are retained in cis at their transcription sites. Purified SUV39H1 directly binds nucleic acids through its chromodomain; and in cells, SUV39H1 associates with α-satellite RNA transcripts. Furthermore, nucleic acid binding mutants destabilize the association of SUV39H1 with chromatin in mitotic and interphase cells - effects that can be recapitulated by RNase treatment or RNA polymerase inhibition - and cause defects in heterochromatin function. Collectively, our findings uncover a previously unrealized function for chromatin-associated RNA in regulating constitutive heterochromatin in human cells.
Asunto(s)
Heterocromatina/metabolismo , Metiltransferasas/metabolismo , ARN/metabolismo , Proteínas Represoras/metabolismo , Línea Celular , Humanos , Unión ProteicaRESUMEN
DNA double-strand breaks (DSBs) serve as obligatory intermediates for Ig heavy chain (Igh) class switch recombination (CSR). The mechanisms by which DSBs are resolved to promote long-range DNA end-joining while suppressing genomic instability inherently associated with DSBs are yet to be fully elucidated. Here, we use a targeted short-hairpin RNA screen in a B-cell lymphoma line to identify the BRCT-domain protein BRIT1 as an effector of CSR. We show that conditional genetic deletion of BRIT1 in mice leads to a marked increase in unrepaired Igh breaks and a significant reduction in CSR in ex vivo activated splenic B cells. We find that the C-terminal tandem BRCT domains of BRIT1 facilitate its interaction with phosphorylated H2AX and that BRIT1 is recruited to the Igh locus in an activation-induced cytidine deaminase (AID) and H2AX-dependent fashion. Finally, we demonstrate that depletion of another BRCT-domain protein, MDC1, in BRIT1-deleted B cells increases the severity of CSR defect over what is observed upon loss of either protein alone. Our results identify BRIT1 as a factor in CSR and demonstrate that multiple BRCT-domain proteins contribute to optimal resolution of AID-induced DSBs.
RESUMEN
During an immune response, activated B cells may undergo class switch recombination (CSR), a molecular rearrangement that allows B cells to switch from expressing IgM and IgD to a secondary antibody heavy chain isotype such as IgG, IgA or IgE. Secondary antibody isotypes provide the adaptive immune system with distinct effector functions to optimally combat various pathogens. CSR occurs between repetitive DNA elements within the immunoglobulin heavy chain (Igh) locus, termed switch (S) regions and requires the DNA-modifying enzyme activation-induced cytidine deaminase (AID). AID-mediated DNA deamination within S regions initiates the formation of DNA double-strand breaks, which serve as biochemical beacons for downstream DNA repair pathways that coordinate the ligation of DNA breaks. Myriad factors contribute to optimal AID targeting; however, many of these factors also localize to genomic regions outside of the Igh locus. Thus, a current challenge is to explain the specific targeting of AID to the Igh locus. Recent studies have implicated noncoding RNAs in CSR, suggesting a provocative mechanism that incorporates Igh-specific factors to enable precise AID targeting. Here, we chronologically recount the rich history of noncoding RNAs functioning in CSR to provide a comprehensive context for recent and future discoveries. We present a model for the RNA-guided targeting of AID that attempts to integrate historical and recent findings, and highlight potential caveats. Lastly, we discuss testable hypotheses ripe for current experimentation, and explore promising ideas for future investigations.
Asunto(s)
Linfocitos B/inmunología , Citidina Desaminasa/metabolismo , Cambio de Clase de Inmunoglobulina , Modelos Inmunológicos , ARN no Traducido/genética , Animales , Citidina Desaminasa/genética , Humanos , Inmunomodulación , Activación de Linfocitos , Ratones , Terapia Molecular Dirigida , Recombinación GenéticaRESUMEN
P53-binding protein 1 (53BP1) is a multi-functional double-strand break repair protein that is essential for class switch recombination in B lymphocytes and for sensitizing BRCA1-deficient tumours to poly-ADP-ribose polymerase-1 (PARP) inhibitors. Central to all 53BP1 activities is its recruitment to double-strand breaks via the interaction of the tandem Tudor domain with dimethylated lysine 20 of histone H4 (H4K20me2). Here we identify an uncharacterized protein, Tudor interacting repair regulator (TIRR), that directly binds the tandem Tudor domain and masks its H4K20me2 binding motif. Upon DNA damage, the protein kinase ataxia-telangiectasia mutated (ATM) phosphorylates 53BP1 and recruits RAP1-interacting factor 1 (RIF1) to dissociate the 53BP1-TIRR complex. However, overexpression of TIRR impedes 53BP1 function by blocking its localization to double-strand breaks. Depletion of TIRR destabilizes 53BP1 in the nuclear-soluble fraction and alters the double-strand break-induced protein complex centring 53BP1. These findings identify TIRR as a new factor that influences double-strand break repair using a unique mechanism of masking the histone methyl-lysine binding function of 53BP1.
Asunto(s)
Proteínas Portadoras/metabolismo , Histonas/química , Histonas/metabolismo , Lisina/metabolismo , Proteína 1 de Unión al Supresor Tumoral P53/antagonistas & inhibidores , Proteína 1 de Unión al Supresor Tumoral P53/metabolismo , Animales , Proteínas de la Ataxia Telangiectasia Mutada/metabolismo , Sitios de Unión , Roturas del ADN de Doble Cadena , Reparación del ADN , Femenino , Humanos , Metilación , Ratones , Ratones Endogámicos C57BL , Fosforilación , Unión Proteica , Dominios Proteicos , Proteínas de Unión al ARN , Proteínas de Unión a Telómeros/metabolismo , Proteína 1 de Unión al Supresor Tumoral P53/químicaAsunto(s)
Biología Molecular , Edición de ARN , Secuencia de Bases , Biología Computacional , Humanos , Datos de Secuencia Molecular , ARNRESUMEN
Generation of cellular heterogeneity is an essential feature of the adaptive immune system. This is best exemplified during humoral immune response when an expanding B cell clone assumes multiple cell fates, including class-switched B cells, antibody-secreting plasma cells, and memory B cells. Although each cell type is essential for immunity, their generation must be exquisitely controlled because a class-switched B cell cannot revert back to the parent isotype, and a terminally differentiated plasma cell cannot contribute to the memory pool. In this study, we show that an environmental sensor, the aryl hydrocarbon receptor (AhR) is highly induced upon B cell activation and serves a critical role in regulating activation-induced cell fate outcomes. We find that AhR negatively regulates class-switch recombination ex vivo by altering activation-induced cytidine deaminase expression. We further demonstrate that AhR suppresses class switching in vivo after influenza virus infection and immunization with model antigens. In addition, by regulating Blimp-1 expression via Bach2, AhR represses differentiation of B cells into plasmablasts ex vivo and antibody-secreting plasma cells in vivo. These experiments suggest that AhR serves as a molecular rheostat in B cells to brake the effector response, possibly to facilitate optimal recall responses. Thus, AhR might represent a novel molecular target for manipulation of B cell responses during vaccination.
Asunto(s)
Linfocitos B/fisiología , Receptores de Hidrocarburo de Aril/fisiología , Animales , Diferenciación Celular , Citidina Desaminasa/fisiología , Femenino , Cambio de Clase de Inmunoglobulina , Subtipo H1N1 del Virus de la Influenza A/inmunología , Masculino , Ratones , Ratones Endogámicos C57BL , Células Plasmáticas/citología , Dibenzodioxinas Policloradas/farmacología , Factor 1 de Unión al Dominio 1 de Regulación Positiva , Linfocitos T/fisiología , Factores de Transcripción/fisiologíaRESUMEN
Small immune complexes cause type III hypersensitivity reactions that frequently result in tissue injury. The responsible mechanisms, however, remain unclear and differ depending on target organs. Here, we identify a kidney-specific anatomical and functional unit, formed by resident macrophages and peritubular capillary endothelial cells, which monitors the transport of proteins and particles ranging from 20 to 700 kDa or 10 to 200 nm into the kidney interstitium. Kidney-resident macrophages detect and scavenge circulating immune complexes "pumped" into the interstitium via trans-endothelial transport and trigger a FcγRIV-dependent inflammatory response and the recruitment of monocytes and neutrophils. In addition, FcγRIV and TLR pathways synergistically "super-activate" kidney macrophages when immune complexes contain a nucleic acid. These data identify a physiological function of tissue-resident kidney macrophages and a basic mechanism by which they initiate the inflammatory response to small immune complexes in the kidney.
Asunto(s)
Enfermedades del Complejo Inmune/inmunología , Riñón/citología , Riñón/inmunología , Macrófagos/inmunología , Animales , Complejo Antígeno-Anticuerpo , Células Endoteliales , Macrófagos/citología , Ratones Endogámicos C57BL , Microscopía Inmunoelectrónica , Monocitos/citología , Monocitos/inmunología , Neutrófilos/citología , Neutrófilos/inmunología , Receptores de IgG/inmunologíaRESUMEN
As B cells engage in the immune response, they express activation-induced cytidine deaminase (AID) to initiate the hypermutation and recombination of immunoglobulin genes, which are crucial processes for the efficient recognition and disposal of pathogens. However, AID must be tightly controlled in B cells to minimize off-target mutations, which can drive chromosomal translocations and the development of B cell malignancies, such as lymphomas. Recent genomic and biochemical analyses have begun to unravel the mechanisms of how AID-mediated deamination is targeted outside immunoglobulin genes. Here, we discuss the transcriptional and topological features that are emerging as key drivers of AID promiscuous activity.