RESUMEN
Follicular T helper (TFH) cells orchestrate the germinal center (GC) response locally. TFH localization in GCs is controlled by chemo-guidance cues and antigen-specific adhesion. Here. we define an antigen-independent, contact-dependent, adhesive guidance system for TFH cells. Unusual for amoeboid cell migration, the system is composed of transmembrane plexin B2 (PlxnB2) molecule, which is highly expressed by GC B cells, and its transmembrane binding partner semaphorin 4C (Sema4C), which is upregulated on TFH cells. Sema4C on TFH cells serves as a receptor to sense the GC-presented PlxnB2 cue and biases TFH migration inwards at the GC edge to promote GC access. The absence of PlxnB2 from the GC or Sema4C from TFH cells causes TFH accumulation along the GC border, impairs T-B cell interactions in the GC, and is associated with defective plasma cell production and affinity maturation. Therefore, Sema4C and PlxnB2 regulate GC TFH recruitment and function and optimize antibody responses.
Asunto(s)
Movimiento Celular , Centro Germinal/citología , Proteínas del Tejido Nervioso/metabolismo , Semaforinas/metabolismo , Linfocitos T Colaboradores-Inductores/metabolismo , Animales , Linfocitos B/fisiología , Células Cultivadas , Centro Germinal/metabolismo , Ratones , Linfocitos T Colaboradores-Inductores/fisiologíaRESUMEN
T follicular helper cells (Tfh cells) localize to follicles where they provide growth and selection signals to mutated germinal center (GC) B cells, thus promoting their differentiation into high affinity long-lived plasma cells and memory B cells. T-dependent B cell differentiation also occurs extrafollicularly, giving rise to unmutated plasma cells that are important for early protection against microbial infections. Bcl-6 expression in T cells has been shown to be essential for the formation of Tfh cells and GC B cells, but little is known about its requirement in physiological extrafollicular antibody responses. We use several mouse models in which extrafollicular plasma cells can be unequivocally distinguished from those of GC origin, combined with antigen-specific T and B cells, to show that the absence of T cell-expressed Bcl-6 significantly reduces T-dependent extrafollicular antibody responses. Bcl-6(+) T cells appear at the T-B border soon after T cell priming and before GC formation, and these cells express low amounts of PD-1. Their appearance precedes that of Bcl-6(+) PD-1(hi) T cells, which are found within the GC. IL-21 acts early to promote both follicular and extrafollicular antibody responses. In conclusion, Bcl-6(+) T cells are necessary at B cell priming to form extrafollicular antibody responses, and these pre-GC Tfh cells can be distinguished phenotypically from GC Tfh cells.
Asunto(s)
Linfocitos B/inmunología , Linfocitos B/metabolismo , Proteínas de Unión al ADN/metabolismo , Linfocitos T/inmunología , Linfocitos T/metabolismo , Animales , Formación de Anticuerpos , Linfocitos B/citología , Diferenciación Celular , Proteínas de Unión al ADN/deficiencia , Proteínas de Unión al ADN/genética , Centro Germinal/citología , Centro Germinal/inmunología , Centro Germinal/metabolismo , Interleucinas/deficiencia , Interleucinas/metabolismo , Cooperación Linfocítica , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Ratones Transgénicos , Células Plasmáticas/citología , Células Plasmáticas/inmunología , Células Plasmáticas/metabolismo , Proteínas Proto-Oncogénicas c-bcl-6 , Salmonelosis Animal/inmunología , Salmonella enterica , Linfocitos T/citología , Quimera por Trasplante/inmunología , Quimera por Trasplante/metabolismoRESUMEN
Effective vaccine adjuvants must induce expression of major histocompatibility (MHC) class II proteins and the costimulatory molecule CD86 on dendritic cells (DCs). However, some adjuvants elicit production of cytokines resulting in adverse inflammatory consequences. Development of agents that selectively increase MHC class II and CD86 expression without triggering unwanted cytokine production requires a better understanding of the molecular mechanisms influencing the production and degradation of MHC class II and CD86 in DCs. Here, we investigate how CD83, an immunoglobulin protein expressed on the surface of mature DCs, promotes MHC class II and CD86 expression. Using mice with an N-ethyl-N-nitrosourea-induced mutation eliminating the transmembrane (TM) region of CD83, we found that the TM domain of CD83 enhances MHC class II and CD86 expression by blocking MHC class II association with the ubiquitin ligase MARCH1. The TM region of CD83 blocks interleukin 10-driven, MARCH1-dependent ubiquitination and degradation of MHC class II and CD86 in DCs. Exploiting this posttranslational pathway for boosting MHC class II and CD86 expression on DCs may provide an opportunity to enhance the immunogenicity of vaccines.
Asunto(s)
Antígenos CD/inmunología , Antígeno B7-2/inmunología , Antígenos de Histocompatibilidad Clase II/inmunología , Inmunoglobulinas/inmunología , Interleucina-10/inmunología , Glicoproteínas de Membrana/inmunología , Ubiquitina-Proteína Ligasas/metabolismo , Ubiquitinación , Secuencia de Aminoácidos , Animales , Antígenos CD/química , Antígenos CD/genética , Secuencia de Bases , Membrana Celular/inmunología , Células Dendríticas/inmunología , Células HEK293 , Humanos , Inmunoglobulinas/química , Inmunoglobulinas/genética , Masculino , Glicoproteínas de Membrana/química , Glicoproteínas de Membrana/genética , Ratones , Datos de Secuencia Molecular , Alineación de Secuencia , Ubiquitina-Proteína Ligasas/inmunología , Antígeno CD83RESUMEN
During T cell-dependent responses, B cells can either differentiate extrafollicularly into short-lived plasma cells or enter follicles to form germinal centers (GCs). Interactions with T follicular helper (Tfh) cells are required for GC formation and for selection of somatically mutated GC B cells. Interleukin (IL)-21 has been reported to play a role in Tfh cell formation and in B cell growth, survival, and isotype switching. To date, it is unclear whether the effect of IL-21 on GC formation is predominantly a consequence of this cytokine acting directly on the Tfh cells or if IL-21 directly influences GC B cells. We show that IL-21 acts in a B cell-intrinsic fashion to control GC B cell formation. Mixed bone marrow chimeras identified a significant B cell-autonomous effect of IL-21 receptor (R) signaling throughout all stages of the GC response. IL-21 deficiency profoundly impaired affinity maturation and reduced the proportion of IgG1(+) GC B cells but did not affect formation of early memory B cells. IL-21R was required on GC B cells for maximal expression of Bcl-6. In contrast to the requirement for IL-21 in the follicular response to sheep red blood cells, a purely extrafollicular antibody response to Salmonella dominated by IgG2a was intact in the absence of IL-21.
Asunto(s)
Linfocitos B/inmunología , Proteínas de Unión al ADN/biosíntesis , Centro Germinal/inmunología , Interleucinas/metabolismo , Animales , Linfocitos B/metabolismo , Linfocitos T CD4-Positivos/inmunología , Comunicación Celular/inmunología , Diferenciación Celular/inmunología , Proteínas de Unión al ADN/inmunología , Centro Germinal/citología , Isotipos de Inmunoglobulinas/biosíntesis , Isotipos de Inmunoglobulinas/genética , Interleucinas/inmunología , Ratones , Ratones Endogámicos C57BL , Proteínas Proto-Oncogénicas c-bcl-6 , Receptores de Interleucina-21/inmunología , Receptores de Interleucina-21/metabolismo , Ovinos , Transducción de Señal/inmunología , Linfocitos T Colaboradores-Inductores/inmunologíaRESUMEN
Over the past few decades, multiple mechanisms have emerged that operate to prune the lymphocyte repertoire of self-reactive specificities and maintain immunological tolerance. Multiple families of small noncoding RNAs known as microRNAs (miRNAs) target immune transcripts to fine-tune gene expression and turn on negative feedback loops. Both of these actions are crucial to limit co-stimulation, set precise cellular activation thresholds, curtail inflammation, control lymphocyte growth, and maintain regulatory T cell homeostasis and suppressive function. Analysis of predicted miRNA-mediated regulation of 72 lupus susceptibility genes in humans and mice reveals most contain numerous target sites for over 140 miRNAs conserved in mammals. MECP2, ROQUIN/RC3H1, BCL2, BIM, and PTEN contain over 50 miRNA target sites each, highlighting the need to control their final protein products with enormous precision to maintain the balance between immunity and tolerance. Overlap among targets of individual miRNAs is considerable, with each miRNA targeting a median of nine autoimmune genes. Three miRNAs--miR-181, miR-186, and miR-590-3p--together are predicted to target over 50% of all lupus genes. Also, a single miRNA cluster located at 14q32.31 containing 11 miRNAs is predicted to regulate 48 lupus susceptibility genes. Dysregulation of single or a few miRNAs or miRNA clusters can result from genetic variation, hormonal influences, or environmental triggers including EBV infection. In the light of this vast and promiscuous miRNA-mediated regulation of autoimmune genes it is anticipated that changes in miRNA levels or their target sequences will help explain susceptibility to complex autoimmune diseases.
Asunto(s)
Autoinmunidad/genética , Regulación de la Expresión Génica/inmunología , MicroARNs/inmunología , Animales , Expresión Génica , Humanos , Tolerancia Inmunológica/genética , RatonesRESUMEN
During evolutionary adaptation in the immune system, host defense is traded off against autoreactivity. Signals through the costimulatory receptor CD28 enable T cells to respond specifically to pathogens, whereas those through the related costimulatory receptor, ICOS, which arose by gene duplication, are critical for affinity maturation and memory antibody responses. ICOS ligand, unlike the pathogen-inducible CD28 ligands, is widely and constitutively expressed in the immune system. Here, we show that crosstalk between these two pathways provides a mechanism for obviating the normal T cell dependence on CD28. Several CD28-mediated responses-generation of follicular helper T cells, germinal center formation, T helper 1 cell-dependent extrafollicular antibody responses to Salmonella and bacterial clearance, and regulatory T cell homeostasis-became independent of CD28 and dependent on ICOS when the E3 ubiquitin ligase Roquin was mutated. Mechanisms to functionally compartmentalize ICOS and CD28 signals are thus critical for two-signal control of normal immune reactions.
Asunto(s)
Antígenos de Diferenciación de Linfocitos T/inmunología , Antígenos CD28/inmunología , Linfocitos T/inmunología , Ubiquitina-Proteína Ligasas/inmunología , Alelos , Animales , Antígenos de Diferenciación de Linfocitos T/genética , Antígenos de Diferenciación de Linfocitos T/metabolismo , Antígenos CD28/genética , Antígenos CD28/metabolismo , Diferenciación Celular/inmunología , Regulación de la Expresión Génica , Centro Germinal/inmunología , Memoria Inmunológica/inmunología , Proteína Coestimuladora de Linfocitos T Inducibles , Interleucina-2/inmunología , Interleucina-2/metabolismo , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Mutación/genética , Salmonella/inmunología , Transducción de Señal/inmunología , Linfocitos T/citología , Linfocitos T/metabolismo , Timo/citología , Timo/inmunología , Ubiquitina-Proteína Ligasas/genética , Ubiquitina-Proteína Ligasas/metabolismoRESUMEN
Production of high-affinity pathogenic autoantibodies appears to be central to the pathogenesis of lupus. Because normal high-affinity antibodies arise from germinal centers (GCs), aberrant selection of GC B cells, caused by either failure of negative selection or enhanced positive selection by follicular helper T (T(FH)) cells, is a plausible explanation for these autoantibodies. Mice homozygous for the san allele of Roquin, which encodes a RING-type ubiquitin ligase, develop GCs in the absence of foreign antigen, excessive T(FH) cell numbers, and features of lupus. We postulated a positive selection defect in GCs to account for autoantibodies. We first demonstrate that autoimmunity in Roquin(san/san) (sanroque) mice is GC dependent: deletion of one allele of Bcl6 specifically reduces the number of GC cells, ameliorating pathology. We show that Roquin(san) acts autonomously to cause accumulation of T(FH) cells. Introduction of a null allele of the signaling lymphocyte activation molecule family adaptor Sap into the sanroque background resulted in a substantial and selective reduction in sanroque T(FH) cells, and abrogated formation of GCs, autoantibody formation, and renal pathology. In contrast, adoptive transfer of sanroque T(FH) cells led to spontaneous GC formation. These findings identify T(FH) dysfunction within GCs and aberrant positive selection as a pathway to systemic autoimmunity.
Asunto(s)
Autoinmunidad/inmunología , Centro Germinal/citología , Linfocitos T Colaboradores-Inductores/inmunología , Animales , Antígenos de Diferenciación de Linfocitos T/metabolismo , Autoanticuerpos/sangre , Linfocitos B/citología , Linfocitos B/inmunología , Antígenos CD28/metabolismo , Recuento de Células , Proliferación Celular , Proteínas de Unión al ADN/deficiencia , Proteínas de Unión al ADN/metabolismo , Centro Germinal/inmunología , Heterocigoto , Proteína Coestimuladora de Linfocitos T Inducibles , Interleucinas/deficiencia , Lupus Eritematoso Sistémico/sangre , Lupus Eritematoso Sistémico/inmunología , Lupus Eritematoso Sistémico/patología , Activación de Linfocitos , Subgrupos Linfocitarios/citología , Subgrupos Linfocitarios/inmunología , Ratones , Fenotipo , Proteínas Proto-Oncogénicas c-bcl-6 , Linfocitos T Colaboradores-Inductores/trasplante , Células TH1/citología , Células TH1/inmunología , Células Th2/citología , Células Th2/inmunología , Ubiquitina-Proteína Ligasas/metabolismoRESUMEN
PURPOSE OF REVIEW: In this study, we outline the evidence suggesting that defects in the RNA silencing machinery can lead to the prototypic systemic autoimmune disease, systemic lupus erythematosus, and describe the potential for RNA interference to provide novel therapeutic agents. RECENT FINDINGS: Over the last year, a class of small noncoding RNAs--microRNAs--have been shown to play key roles in immune regulation including T-cell selection in the thymus, B cell affinity maturation and selection in germinal centres, and development of regulatory T cells, suggesting that the microRNA machinery may be crucial in the maintenance of immunological tolerance. Two RNA silencing mechanisms have been shown to be involved in lupus pathogenesis: failed Roquin-mediated repression of inducible costimulatory receptors messenger RNA through miR-101 in roquin(san/san) mice and decreased expression of pro-apoptotic molecule and phosphatase and tensin homologue on chromosome 10 in mice transgenic for the miR-17-92 cluster, leading to lymphoproliferation and other lupus manisfestations. MicroRNA array experiments performed on peripheral blood mononuclear cells have revealed different expression profiles in systemic lupus erythematosus patients. RNA interference has also been used ex vivo to silence dysregulated T-cell molecules in cells from systemic lupus erythematosus patients. SUMMARY: Dysregulation of the RNA silencing machinery has been implicated in systemic lupus erythematosus pathogenesis. Although microRNA profiling may prove to be a useful diagnostic and prognostic tool for a notoriously heterogeneous disease, manipulation of RNA interference emerges as a powerful and potentially specific means to correct dysregulated gene expression in systemic lupus erythematosus patients.
Asunto(s)
Lupus Eritematoso Sistémico/genética , Lupus Eritematoso Sistémico/inmunología , MicroARNs/genética , MicroARNs/inmunología , Interferencia de ARN , Animales , Terapia Genética/métodos , Humanos , Lupus Eritematoso Sistémico/terapia , Linfocitos T/fisiologíaRESUMEN
Systemic lupus erythematosus (SLE) is a multisystem autoimmune disorder in which complex genetic factors play an important role. Several strains of gene-targeted mice have been reported to develop SLE, implicating the null genes in the causation of disease. However, hybrid strains between 129 and C57BL/6 mice, widely used in the generation of gene-targeted mice, develop spontaneous autoimmunity. Furthermore, the genetic background markedly influences the autoimmune phenotype of SLE in gene-targeted mice. This suggests an important role in the expression of autoimmunity of as-yet-uncharacterised background genes originating from these parental mouse strains. Using genome-wide linkage analysis, we identified several susceptibility loci, derived from 129 and C57BL/6 mice, mapped in the lupus-prone hybrid (129 x C57BL/6) model. By creating a C57BL/6 congenic strain carrying a 129-derived Chromosome 1 segment, we found that this 129 interval was sufficient to mediate the loss of tolerance to nuclear antigens, which had previously been attributed to a disrupted gene. These results demonstrate important epistatic modifiers of autoimmunity in 129 and C57BL/6 mouse strains, widely used in gene targeting. These background gene influences may account for some, or even all, of the autoimmune traits described in some gene-targeted models of SLE.
Asunto(s)
Autoinmunidad/genética , Autoinmunidad/inmunología , Modelos Genéticos , Animales , Núcleo Celular/metabolismo , Mapeo Cromosómico , Estudios de Cohortes , Modelos Animales de Enfermedad , Epistasis Genética , Femenino , Marcación de Gen , Ligamiento Genético , Predisposición Genética a la Enfermedad , Genoma , Genotipo , Lupus Eritematoso Sistémico/genética , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Repeticiones de Microsatélite , Sitios de Carácter Cuantitativo , Especificidad de la EspecieRESUMEN
Lupus-prone New Zealand Black and New Zealand White mice produce high serum levels of the endogenous retroviral envelope protein gp70 and develop an Ab response to this autoantigen as part of their autoimmune disease. Linkage analysis of two crosses involving New Zealand and BALB/c mice mapped these traits to a group of overlapping loci, including a novel locus on proximal chromosome 12. This locus was linked with serum gp70 and the autoimmune response against it. The linkage of serum gp70 levels to a previously described locus on distal chromosome 4 was also confirmed. Sequence analysis of a candidate gene on distal chromosome 4, Fv1, provided support that this gene may be associated with the control of serum gp70 levels in both New Zealand Black and New Zealand White mice. Linkage data and statistical analysis confirmed a close correlation between gp70 Ag and anti-gp70 Ab levels, and together gave support to the concept that a threshold level of gp70 is required for the production of anti-gp70 Abs. Serum levels of anti-gp70 Abs were closely correlated with the presence of renal disease, more so than anti-dsDNA Abs. Understanding the genetic basis of this complex autoantigen-autoantibody system will provide insight into the pathogenesis of lupus in mice, which may have implications for human disease.
Asunto(s)
Anticuerpos Antivirales/biosíntesis , Regulación de la Expresión Génica/inmunología , Marcadores Genéticos/inmunología , Glicoproteínas/inmunología , Retroviridae/inmunología , Proteínas del Envoltorio Viral/inmunología , Animales , Anticuerpos Antivirales/sangre , Mapeo Cromosómico , Cruzamientos Genéticos , Femenino , Ligamiento Genético , Predisposición Genética a la Enfermedad , Glomerulonefritis/genética , Glomerulonefritis/inmunología , Glicoproteínas/sangre , Ratones , Ratones Congénicos , Ratones Endogámicos BALB C , Ratones Endogámicos NZB , Proteínas/genética , Especificidad de la Especie , Proteínas del Envoltorio Viral/sangreRESUMEN
New Zealand Black (NZB) and New Zealand White (NZW) mice are genetically predisposed to a lupus-like autoimmune syndrome. To further define the loci linked to disease traits in NZB and NZW mice in the context of the BALB/c genetic background, linkage analyses were conducted in two crosses: (NZW x BALB/c.H2(z))F(1) x NZB and (NZB x BALB/c)F(2). Novel loci linked to autoantibody production and glomerulonephritis, present in both NZB and NZW mice, were identified on proximal chromosomes 12 and 4. The chromosome 12 locus showed the strongest linkage to anti-nuclear Ab production. Additionally, a number of other novel loci linked to lupus traits derived from both the New Zealand and non-autoimmune BALB/c genomes were identified. Furthermore, we confirm the linkage of disease to a number of previously described lupus-associated loci, demonstrating that they are relatively background independent. These data provide a number of additional candidate gene regions in murine lupus, and highlight the powerful effect the non-autoimmune background strain has in influencing the genetic loci linked to disease.