RESUMEN
B cells and the antibodies they produce are critical in host defense against pathogens and contribute to various immune-mediated diseases. B cells responding to activating signals in vitro release extracellular vesicles (EV) that carry surface antibodies, yet B cell production of EVs that express antibodies and their function in vivo is incompletely understood. Using transgenic mice expressing the Cre recombinase in B cells switching to IgG1 to induce expression of fusion proteins between emerald green fluorescent protein (emGFP) and the EV tetraspanin CD63 as a model, we identify emGFP expression in B cells responding to foreign antigen in vivo and characterize the emGFP+ EVs they release. Our data suggests that emGFP+ germinal center B cells undergoing immunoglobulin class switching to express IgG and their progeny memory B cells and plasma cells, also emGFP+, are sources of circulating antigen-specific IgG+ EVs. Furthermore, using a mouse model of influenza virus infection, we find that IgG+ EVs specific for the influenza hemagglutinin antigen protect against virus infection. In addition, crossing the B cell Cre driver EV reporter mice onto the Nba2 lupus-prone strain revealed increased circulating emGFP+ EVs that expressed surface IgG against nuclear antigens linked to autoimmunity. These data identify EVs loaded with antibodies as a novel route for antibody secretion in B cells that contribute to adaptive immune responses, with important implications for different functions of IgG+ EVs in infection and autoimmunity.
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Linfocitos B , Vesículas Extracelulares , Inmunoglobulina G , Ratones Transgénicos , Animales , Vesículas Extracelulares/inmunología , Vesículas Extracelulares/metabolismo , Inmunoglobulina G/inmunología , Inmunoglobulina G/metabolismo , Ratones , Linfocitos B/inmunología , Linfocitos B/metabolismo , Infecciones por Orthomyxoviridae/inmunología , Proteínas Fluorescentes Verdes/metabolismo , Proteínas Fluorescentes Verdes/genética , Antígenos/inmunología , Cambio de Clase de Inmunoglobulina , Ratones Endogámicos C57BL , Centro Germinal/inmunología , Centro Germinal/metabolismoRESUMEN
Recent studies have demonstrated a role for Ten-Eleven Translocation-2 (TET2), an epigenetic modulator, in regulating germinal center formation and plasma cell differentiation in B-2 cells, yet the role of TET2 in regulating B-1 cells is largely unknown. Here, B-1 cell subset numbers, IgM production, and gene expression were analyzed in mice with global knockout of TET2 compared to wildtype (WT) controls. Results revealed that TET2-KO mice had elevated numbers of B-1a and B-1b cells in their primary niche, the peritoneal cavity, as well as in the bone marrow (B-1a) and spleen (B-1b). Consistent with this finding, circulating IgM, but not IgG, was elevated in TET2-KO mice compared to WT. Analysis of bulk RNASeq of sort purified peritoneal B-1a and B-1b cells revealed reduced expression of heavy and light chain immunoglobulin genes, predominantly in B-1a cells from TET2-KO mice compared to WT controls. As expected, the expression of IgM transcripts was the most abundant isotype in B-1 cells. Yet, only in B-1a cells there was a significant increase in the proportion of IgM transcripts in TET2-KO mice compared to WT. Analysis of the CDR3 of the BCR revealed an increased abundance of replicated CDR3 sequences in B-1 cells from TET2-KO mice, which was more clearly pronounced in B-1a compared to B-1b cells. V-D-J usage and circos plot analysis of V-J combinations showed enhanced usage of VH11 and VH12 pairings. Taken together, our study is the first to demonstrate that global loss of TET2 increases B-1 cell number and IgM production and reduces CDR3 diversity, which could impact many biological processes and disease states that are regulated by IgM.
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Subgrupos de Linfocitos B , Ratones , Animales , Subgrupos de Linfocitos B/metabolismo , Linfocitos B , Cadenas Ligeras de Inmunoglobulina/genética , Translocación Genética , Inmunoglobulina M , Recuento de CélulasRESUMEN
The recent recognition of a syndrome of tick-acquired mammalian meat allergy has transformed the previously held view that mammalian meat is an uncommon allergen. The syndrome, mediated by IgE antibodies against the oligosaccharide galactose-alpha-1,3-galactose (alpha-gal), can also involve reactions to visceral organs, dairy, gelatin and other products, including medications sourced from non-primate mammals. Thus, fittingly, this allergic disorder is now called the alpha-gal syndrome (AGS). The syndrome is strikingly regional, reflecting the important role of tick bites in sensitization, and is more common in demographic groups at risk of tick exposure. Reactions in AGS are delayed, often by 2-6 h after ingestion of mammalian meat. In addition to classic allergic symptomatology such as urticaria and anaphylaxis, AGS is increasingly recognized as a cause of isolated gastrointestinal morbidity and alpha-gal sensitization has also been linked with cardiovascular disease. The unusual link with tick bites may be explained by the fact that allergic cells and mediators are mobilized to the site of tick bites and play a role in resistance against ticks and tick-borne infections. IgE directed to alpha-gal is likely an incidental consequence of what is otherwise an adaptive immune strategy for host defense against endo- and ectoparasites, including ticks.
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Anafilaxia , Hipersensibilidad a los Alimentos , Inmunoglobulina E , Mordeduras de Garrapatas , Enfermedades por Picaduras de Garrapatas , Urticaria , Animales , Humanos , Alérgenos/inmunología , Anafilaxia/inmunología , Anafilaxia/etiología , Anafilaxia/diagnóstico , Disacáridos/inmunología , Hipersensibilidad a los Alimentos/inmunología , Hipersensibilidad a los Alimentos/etiología , Inmunoglobulina E/inmunología , Mamíferos/inmunología , Carne/efectos adversos , Síndrome , Mordeduras de Garrapatas/inmunología , Mordeduras de Garrapatas/complicaciones , Garrapatas/inmunología , Urticaria/inmunología , Urticaria/etiología , Enfermedades por Picaduras de Garrapatas/inmunologíaRESUMEN
BACKGROUND: tumor-infiltrating lymphocytes are prognostic in many human cancers. However, the prognostic value of lymphocytes infiltrating glioblastoma (GBM), and roles in tumor control or progression are unclear. We hypothesized that B and T cell density, and markers of their activity, proliferation, differentiation, or function, would have favorable prognostic significance for patients with GBM. METHODS: initial resection specimens from 77 patients with IDH1/2 wild type GBM who received standard-of-care treatment were evaluated with multiplex immunofluorescence histology (mIFH), for the distribution, density, differentiation, and proliferation of T cells and B cells, as well as for the presence of tertiary lymphoid structures (TLS), and IFNγ expression. Immune infiltrates were evaluated for associations with overall survival (OS) by univariate and multivariate Cox proportional hazards modeling. RESULTS: in univariate analyses, improved OS was associated with high densities of proliferating (Ki67+) CD8+ cells (HR 0.36, p = 0.001) and CD20+ cells (HR 0.51, p = 0.008), as well as CD8+Tbet+ cells (HR 0.46, p = 0.004), and RORγt+ cells (HR 0.56, p = 0.04). Conversely, IFNγ intensity was associated with diminished OS (HR 0.59, p = 0.036). In multivariable analyses, adjusting for clinical variables, including age, resection extent, Karnofsky Performance Status (KPS), and MGMT methylation status, improved OS was associated with high densities of proliferating (Ki67+) CD8+ cells (HR 0.15, p < 0.001), and higher ratios of CD8+ cells to CD4+ cells (HR 0.31, p = 0.005). Diminished OS was associated with increases in patient age (HR 1.21, p = 0.005) and higher mean intensities of IFNγ (HR 2.13, p = 0.027). CONCLUSIONS: intratumoral densities of proliferating CD8 T cells and higher CD8/CD4 ratios are independent predictors of OS in patients with GBM. Paradoxically, higher mean intensities of IFNγ in the tumors were associated with shorter OS. These findings suggest that survival may be enhanced by increasing proliferation of tumor-reactive CD8+ T cells and that approaches may be needed to promote CD8+ T cell dominance in GBM, and to interfere with the immunoregulatory effects of IFNγ in the tumor microenvironment.
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Linfocitos T CD8-positivos/inmunología , Glioblastoma/inmunología , Glioblastoma/patología , Linfocitos B/inmunología , Biomarcadores de Tumor/metabolismo , Agregación Celular , Recuento de Células , Diferenciación Celular , Proliferación Celular , Femenino , Humanos , Linfocitos Infiltrantes de Tumor/inmunología , Masculino , Persona de Mediana Edad , Análisis Multivariante , Análisis de SupervivenciaRESUMEN
Background: Recent studies have suggested that IgE sensitization to α-gal is associated with coronary artery disease (CAD). However, the B cell subtype(s) responsible for production of IgE to α-gal and mechanisms mediating this production remain elusive. Methods: Single cell multi-omics sequencing, was utilized to phenotype B cells obtained from 60 subjects that had undergone coronary angiography in whom serum IgE was evaluated by ImmunoCAP. Bioinformatics approaches were used to identify B cell subtype(s) and transcriptomic signatures associated with α-gal sensitization. In vitro characterization of chemokine/chemokine receptor pairs on switched memory B cells associated with IgE to α-gal was performed. Results: Of the 60 patients, 17 (28%) were positive for IgE to α-gal. CITESeq identified CCR6+ class-switched memory (SWM) B cells and CXCR4 expresssion on these CCR6+ SWM B cells as significantly associated with IgE sensitization to α-gal but not to other common allergens (peanut or inhalants). In vitro studies of enriched human B cells revealed significantly greater IgE on SWM B cells with high CCR6 and CXCR4 expression 10 days after cells were treated with IL-4 and CD40 to stimulate class switch recombination. Both CCL20 (CCR6 ligand) and CXCL12 (ligand for CXCR4) increased the expression of IgE on SWM B cells expressing their receptors. However, they appeared to have unique pathways mediating this effect as only CCL20 increased activation-induced cytidine deaminase (AID), while CXCL12 drove proliferation of CXCR4+ SWM B cells. Lastly, correlation analysis indicated an association between CAD severity and the frequency of both CCR6+ SWM and CXCR4+ SWM B cells. Conclusions: CCR6+ SWM B cells were identified as potential producers of IgE to α-gal in CAD patients. Additionally, our findings highlighted non-chemotaxis roles of CCL20/CCR6 and CXCL12/CXCR4 signaling in mediating IgE class switching and cell proliferation of SWM B cells respectively. Results may have important implications for a better understanding and better therapeutic approaches for subjects with IgE sensitization to α-gal.
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Allergic diseases represent a major cause of morbidity in modern industrialized and developing countries. The origins and development of allergic immune responses have proven difficult to unravel and remain an important scientific objective. House dust mites (HDM) and ticks represent two important causes of allergic disease. Investigations into HDM fecal particles and tick bites have revealed insights which have and will continue to shape our understanding of allergic immunity. In the present review, focus is given to the role of innate immunity in shaping the respective responses to HDM and ticks. The HDM fecal particle represents a rich milieu of molecules that can be recognized by pathogen-recognition receptors of the innate immune system. Factors in tick saliva and/or tissue damage resultant from tick feeding are thought to activate innate immune signaling that promotes allergic pathways. Recent evidence indicates that innate sensing involves not only the direct recognition of allergenic agents/organisms, but also indirect sensing of epithelial barrier disruption. Although fecal particles from HDM and bites from ticks represent two distinct causes of sensitization, both involve a complex array of molecules that contribute to an innate response. Identification of specific molecules will inform our understanding of the mechanisms that contribute to allergic immunity, however the key may lie in the combination of molecules delivered to specific sites in the body.
RESUMEN
Studies of meat allergic patients have shown that eating meat poses a serious acute health risk that can induce severe cutaneous, gastrointestinal, and respiratory reactions. Allergic reactions in affected individuals following meat consumption are mediated predominantly by IgE antibodies specific for galactose-α-1,3-galactose (α-gal), a blood group antigen of non-primate mammals and therefore present in dietary meat. α-gal is also found within certain tick species and tick bites are strongly linked to meat allergy. Thus, it is thought that exposure to tick bites promotes cutaneous sensitization to tick antigens such as α-gal, leading to the development of IgE-mediated meat allergy. The underlying immune mechanisms by which skin exposure to ticks leads to the production of α-gal-specific IgE are poorly understood and are key to identifying novel treatments for this disease. In this review, we summarize the evidence of cutaneous exposure to tick bites and the development of mammalian meat allergy. We then provide recent insights into the role of B cells in IgE production in human patients with mammalian meat allergy and in a novel mouse model of meat allergy. Finally, we discuss existing data more generally focused on tick-mediated immunomodulation, and highlight possible mechanisms for how cutaneous exposure to tick bites might affect B cell responses in the skin and gut that contribute to loss of oral tolerance.
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Linfocitos B/inmunología , Susceptibilidad a Enfermedades/inmunología , Hipersensibilidad a los Alimentos/etiología , Alérgenos/inmunología , Animales , Linfocitos B/metabolismo , Hipersensibilidad a los Alimentos/metabolismo , Humanos , Inmunoglobulina E/inmunología , Activación de Linfocitos/genética , Activación de Linfocitos/inmunología , Mamíferos , Células Plasmáticas/inmunología , Células Plasmáticas/metabolismo , Carne Roja/efectos adversosRESUMEN
Tick-borne allergies are a growing public health concern and have been associated with the induction of IgE-mediated food allergy to red meat. However, despite the increasing prevalence of tick bite-induced allergies, the mechanisms by which cutaneous exposure to ticks leads to sensitization and the production of IgE Abs are poorly understood. To address this question, an in vivo approach was used to characterize the IgE response to lone star tick proteins administered through the skin of mice. The results demonstrated that tick sensitization and challenge induced a robust production of IgE Abs and supported a role for IgE-mediated hypersensitivity reactions in sensitized animals following oral administration of meat. The induction of IgE responses was dependent on cognate CD4+ T cell help during both the sensitization phase and challenge phase with cutaneous tick exposure. In addition, IgE production was dependent on B cell-intrinsic MyD88 expression, suggesting an important role for TLR signaling in B cells to induce IgE responses to tick proteins. This model of tick-induced IgE responses could be used to study the factors within tick bites that cause allergies and to investigate how sensitization to food Ags occurs through the skin that leads to IgE production.
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Linfocitos T CD4-Positivos/inmunología , Hipersensibilidad a los Alimentos/inmunología , Proteínas de Insectos/inmunología , Factor 88 de Diferenciación Mieloide/inmunología , Mordeduras de Garrapatas/inmunología , Alérgenos/inmunología , Animales , Inmunoglobulina E/inmunología , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Piel/inmunología , Garrapatas/inmunologíaRESUMEN
BACKGROUND: B cells play a critical role in the development and maintenance of food allergy by producing allergen-specific IgE. Despite the importance of B cells in IgE-mediated food allergy, the identity of sIgE-producing human B cells and how IgE is regulated are poorly understood. OBJECTIVE: To identify the immunophenotypes of circulating B cells associated with the production of galactose-alpha-1,3-galactose-specific IgE production in patients with red meat allergy. METHODS: B cells in PBMC samples obtained from 19 adults with physician-diagnosed red meat allergy and 20 non-meat allergic healthy controls were assessed by mass cytometry along with a bioinformatics analysis pipeline to identify discrete B cell phenotypes that associated with serum sIgE. Fluorescent flow cytometry was then applied to sort purify discrete B cell subsets, and B cells were functionally evaluated on an individual cell level for the production of sIgE by ELISPOT. RESULTS: Discrete B cell phenotypes abundant in meat allergic subjects compared to non-meat allergic controls were found in peripheral blood that do not share typical characteristics of classical isotype-switched memory B cells that express high levels of CD27. These B cell subsets shared higher IgD and lower IgM expression levels coupled with CXCR4, CCR6 and CD25 expression. In vitro polyclonal stimulation of purified B cell subsets from meat allergic subjects demonstrated that these subsets were enriched for cells induced to secrete sIgE. CONCLUSIONS AND CLINICAL RELEVANCE: Circulating B cells display increased abundance of discrete B cell subsets in meat allergic subjects. This observation, coupled with the capacity of individual B cell subsets to produce sIgE following activation, implicates these novel B cell phenotypes in promoting IgE in meat allergy.
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Subgrupos de Linfocitos B/inmunología , Citometría de Flujo , Hipersensibilidad a los Alimentos/inmunología , Carne Roja/efectos adversos , Adulto , Anciano , Subgrupos de Linfocitos B/metabolismo , Biomarcadores , Estudios de Casos y Controles , Análisis por Conglomerados , Manejo de la Enfermedad , Femenino , Citometría de Flujo/métodos , Hipersensibilidad a los Alimentos/sangre , Hipersensibilidad a los Alimentos/diagnóstico , Humanos , Inmunoglobulina E/inmunología , Inmunofenotipificación , Leucocitos Mononucleares/inmunología , Leucocitos Mononucleares/metabolismo , Recuento de Linfocitos , Masculino , Persona de Mediana Edad , Adulto JovenRESUMEN
BACKGROUND: The elderly host is highly susceptible to severe disease and treatment failure in Clostridium difficile infection (CDI). We investigated how treatment with vancomycin in the aged host influences systemic and intestinal humoral responses and select intestinal microbiota. METHODS: Young (age, 2 months) and aged (age, 18 months) C57BL/6 mice were infected with VPI 10463 after exposure to broad-spectrum antibiotics. Vancomycin was given 24 hours after infection, and treatment was continued for 5 days. At select time points, specimens of serum and intestinal tissue and contents were collected for histopathologic analysis, to measure antibody levels and the pathogen burden, and to determine the presence and levels of select intestinal microbiota and C. difficile toxin. RESULTS: Levels of disease severity, relapse, and mortality were increased, and recovery from infection was slower in aged mice compared to young mice. Serum levels of immunoglobulin M, immunoglobulin A, and immunoglobulin G against C. difficile toxin A were depressed in aged mice, and vancomycin treatment reduced antibody responses in both age groups. While baseline levels of total bacterial load, Bacteroidetes, Firmicutes, and Enterobacteriaceae were mostly similar, aged mice had a significant change in the Firmicutes to Bacteroidetes ratio with vancomycin treatment. CONCLUSIONS: Vancomycin treatment decreases the systemic humoral response to CDI. Increased mortality from and recurrence of CDI in the aged host are associated with an impaired humoral response and a greater susceptibility to vancomycin-induced alteration of intestinal microbiota.
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Antibacterianos/uso terapéutico , Clostridioides difficile/efectos de los fármacos , Infecciones por Clostridium/tratamiento farmacológico , Microbioma Gastrointestinal/efectos de los fármacos , Inmunidad Humoral/efectos de los fármacos , Vancomicina/uso terapéutico , Factores de Edad , Animales , Humanos , Ratones Endogámicos C57BL , Modelos AnimalesRESUMEN
IgE-mediated hypersensitivity refers to immune reactions that can be rapidly progressing and, in the case of anaphylaxis, are occasionally fatal. To that end, identification of the associated allergen is important for facilitating both education and allergen avoidance that are essential to long-term risk reduction. As the number of known exposures associated with anaphylaxis is limited, discovery of novel causative agents is crucial to evaluation and management of patients with idiopathic anaphylaxis. Within the last 10 years several apparently separate observations were recognized to be related, all of which resulted from the development of antibodies to a carbohydrate moiety on proteins. Interestingly, the exposure differed from airborne allergens but was nevertheless capable of producing anaphylactic and hypersensitivity reactions. Our recent work has identified these responses as being due to a novel IgE antibody directed against a mammalian oligosaccharide epitope, galactose-alpha-1,3-galactose ("alpha-gal"). This review will present the historical summary of the identification of cetuximab hypersensitivity due to alpha-gal IgE and discuss the non-primate mammalian meat food allergy as well as current goals and directions of our research programs.
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Alérgenos/inmunología , Anafilaxia/etiología , Hipersensibilidad a los Alimentos/etiología , Hipersensibilidad Tardía/etiología , Carne/efectos adversos , Oligosacáridos/inmunología , Anafilaxia/inmunología , Animales , Cetuximab/efectos adversos , Hipersensibilidad a las Drogas/inmunología , Hipersensibilidad a los Alimentos/inmunología , Humanos , Hipersensibilidad Tardía/inmunología , Inmunoglobulina E/inmunología , Mordeduras de Garrapatas , GarrapatasRESUMEN
OBJECTIVE: Follicular helper T (Tfh) cells are critical for the development of protective antibodies via germinal center (GC) B cell responses; however, uncontrolled Tfh cell expansion activates autoreactive B cells to produce antibodies that cause autoimmunity. The mechanisms that control Tfh cell homeostasis remain largely unknown. The aim of this study was to determine the contribution of BAFF to Tfh cell responses in autoimmunity. METHODS: We analyzed the properties of Tfh cells in lupus-prone mice sufficient or deficient in BCMA. Adoptive transfer studies and mixed bone marrow chimeras were used to test BCMA signaling in T cells. We assessed BAFF stimulation of Tfh cells through in vitro cell cocultures and in vivo depletion studies using flow cytometry. RESULTS: In Nba2 mice, Tfh cells expressed the BAFF receptors BCMA and B lymphocyte stimulator receptor 3 (BR-3) and accumulated in the spleen when BCMA was absent. BCMA deficiency in T cells promoted the expansion of Tfh cells, GC formation, autoantibody production, and interferon-γ (IFNγ) production by Tfh cells through BR-3. IFNγ-producing Tfh cells increased BAFF expression in dendritic cells. Blocking BAFF or IFNγ in vivo reduced Tfh cell accumulation and reduced autoimmunity in BCMA-deficient animals. Moreover, circulating Tfh-like cells that expressed BR-3 (but not BCMA) were elevated in patients with systemic lupus erythematosus, and this correlated with serum BAFF and IFNγ levels. CONCLUSION: In Nba2 mice, BCMA negatively regulates Tfh cell expansion, while BAFF signaling through BR-3 promotes Tfh cell accumulation. Our findings suggest that the balance between BCMA and BR-3 signaling in Tfh cells serves as a checkpoint of immune tolerance.
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Autoinmunidad/inmunología , Factor Activador de Células B/fisiología , Interferón gamma/metabolismo , Lupus Eritematoso Sistémico/inmunología , Linfocitos T Colaboradores-Inductores/inmunología , Adulto , Animales , Receptor del Factor Activador de Células B/metabolismo , Antígeno de Maduración de Linfocitos B/metabolismo , Técnicas de Cocultivo , Ensayo de Inmunoadsorción Enzimática , Femenino , Citometría de Flujo , Técnica del Anticuerpo Fluorescente , Humanos , Ratones , Ratones Endogámicos C57BL , Persona de Mediana Edad , Reacción en Cadena en Tiempo Real de la Polimerasa , Terpenos/farmacologíaRESUMEN
Despite increased frequencies of neutrophils found in autoimmune diseases such as systemic lupus erythematosus (SLE), how they contribute to disease pathogenesis and the mechanisms that affect the accumulation of neutrophils are poorly understood. The aim of this study was to identify factors in autoantibody-mediated autoimmunity that controls the accumulation of spleen resident neutrophils and to determine whether neutrophils contribute to abnormal B cell responses. Increased levels of the cytokine BAFF have been linked to loss of B cell tolerance in autoimmunity, but the cellular source responsible for excess BAFF is unknown. B cell maturation antigen (BCMA) is a receptor for BAFF and is critical for the survival of bone marrow plasma cells. Paradoxically, BCMA deficiency exacerbates the formation of autoantibody-secreting plasma cells in spleens of lupus-prone mice and the reasons for this effect are not understood. Here we analyzed the phenotype, localization and function of neutrophils in spleens of healthy mice and congenic lupus-prone mice, and compared mice sufficient or deficient in BCMA expression. Neutrophils were found to be significantly increased in frequency and activation status in spleens of lupus-prone mice when BCMA was absent. Furthermore, neutrophils localized within T cell zones and enhanced CD4(+) T cell proliferation and IFNγ production through the production of BAFF. Reduced BAFF and IFNγ serum levels, decreased frequencies of IFNγ-producing T cells, germinal center B cells, and autoantibody production after neutrophil depletion indicated the involvement of neutrophils in these autoimmune traits. Thus, we have identified a novel role for BCMA to control excess BAFF production in murine lupus through restraining the accumulation of BAFF-producing neutrophils. Our data suggests that devising therapeutic strategies to reduce neutrophils in autoimmunity may decrease BAFF levels and ameliorate disease.
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Autoinmunidad/inmunología , Factor Activador de Células B/metabolismo , Antígeno de Maduración de Linfocitos B/metabolismo , Lupus Eritematoso Sistémico/genética , Animales , Autoinmunidad/genética , Factor Activador de Células B/inmunología , Antígeno de Maduración de Linfocitos B/inmunología , Linfocitos B/inmunología , Linfocitos T CD4-Positivos/inmunología , Modelos Animales de Enfermedad , Femenino , Humanos , Lupus Eritematoso Sistémico/inmunología , Lupus Eritematoso Sistémico/patología , Ratones , Neutrófilos/inmunología , Neutrófilos/patología , Bazo/inmunología , Bazo/patología , Linfocitos T/inmunologíaRESUMEN
The long-term survival of plasma cells is entirely dependent on signals derived from their environment. These extrinsic factors presumably induce and sustain the expression of antiapoptotic proteins of the Bcl-2 family. It is uncertain whether there is specificity among Bcl-2 family members in the survival of plasma cells and whether their expression is linked to specific extrinsic factors. We found here that deletion of the gene encoding the antiapoptotic protein Mcl-1 in plasma cells resulted in rapid depletion of this population in vivo. Furthermore, we found that the receptor BCMA was needed to establish high expression of Mcl-1 in bone marrow but not spleen plasma cells and that establishing this survival pathway preceded the component of plasma cell differentiation that depends on the transcriptional repressor Blimp-1. Our results identify a critical role for Mcl-1 in the maintenance of plasma cells.
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Antígeno de Maduración de Linfocitos B/metabolismo , Células Plasmáticas/fisiología , Proteínas Proto-Oncogénicas c-bcl-2/metabolismo , Factores de Transcripción/metabolismo , Animales , Médula Ósea/inmunología , Médula Ósea/metabolismo , Células de la Médula Ósea/citología , Células de la Médula Ósea/metabolismo , Diferenciación Celular , Supervivencia Celular , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Proteína 1 de la Secuencia de Leucemia de Células Mieloides , Células Plasmáticas/citología , Factor 1 de Unión al Dominio 1 de Regulación Positiva , Proteínas Proto-Oncogénicas c-bcl-2/genética , Bazo/inmunologíaRESUMEN
B cell maturation antigen (BCMA) is a tumor necrosis family receptor (TNFR) member that is predominantly expressed on terminally differentiated B cells and, upon binding to its ligands B cell activator of the TNF family (BAFF) and a proliferation inducing ligand (APRIL), delivers pro-survival cell signals. Thus, BCMA is mostly known for its functional activity in mediating the survival of plasma cells that maintain long-term humoral immunity. The expression of BCMA has also been linked to a number of cancers, autoimmune disorders, and infectious diseases that suggest additional roles for BCMA activity. Despite recent advances in our understanding of the roles for the related TNFR members BAFF-R and transmembrane activator and calcium-modulator and cyclophilin ligand interactor (TACI), the signaling pathway used by BCMA for mediating plasma cell survival as well as its putative function in certain disease states are not well understood. By examining the expression, regulation, and signaling targets of BCMA, we may gain further insight into this receptor and how it operates within cells in both health and disease. This information is important for identifying new therapeutic targets that may be relevant in treating diseases that involve the BAFF/APRIL cytokine network.
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Antígeno de Maduración de Linfocitos B/metabolismo , Animales , Antígeno de Maduración de Linfocitos B/genética , Antígeno de Maduración de Linfocitos B/inmunología , HumanosRESUMEN
Neutrophils are an important cellular component of the innate immune system that provides immediate protection to the host from infection. Neutrophil infiltration into inflamed peripheral tissues during infection is beneficial for immunity through phagocytosis of microbes, the release of antimicrobial factors, and secretion of proinflammatory cytokines. Recent reports further suggest that spleen-infiltrating neutrophils play a role in the adaptive immune response by providing survival signals to B cells. However, neutrophils may have detrimental effects on immunity in inflammatory diseases where their recruitment to lymphoid tissues and activation occur abnormally. To determine the contribution of neutrophils that reside in secondary lymphoid tissues to adaptive immunity, direct evaluation of the functional properties of tissue-resident neutrophils is required. We have developed a modified magnetic bead isolation approach for purifying neutrophils from inflamed spleens of autoimmune-prone mice by negative selection. Using this approach, we yielded neutrophils with greater than 90% purity without compromising cell viability. Equally important, the isolation procedure had little effect on the activation of neutrophils and did not impair phagocytic function. Thus, isolation of spleen-resident neutrophils by this optimized approach could be useful for interrogating the functional role of murine neutrophils in normal and abnormal immune responses.
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Neutrófilos/citología , Bazo/citología , Animales , Antígenos CD/metabolismo , Autoinmunidad , Separación Celular , Supervivencia Celular , Centrifugación por Gradiente de Densidad , Femenino , Citometría de Flujo , Interacciones Huésped-Patógeno , Ratones , Ratones Endogámicos C57BL , Neutrófilos/metabolismo , Neutrófilos/microbiología , Fagocitosis , Bazo/inmunología , Staphylococcus aureus/fisiologíaRESUMEN
Genome-wide association studies have identified lupus susceptibility genes such as IRF5 and PRDM1 (encoding for IFN regulatory factor 5 [IRF]5 and Blimp-1) in the human genome. Accordingly, the murine Irf5 and Prdm1 genes have been shown to play a role in lupus susceptibility. However, it remains unclear how IRF5 and Blimp-1 (a transcriptional target of IRF5) contribute to lupus susceptibility. Given that the murine lupus susceptibility locus Nba2 includes the IFN-regulated genes Ifi202 (encoding for the p202 protein), Aim2 (encoding for the Aim2 protein), and Fcgr2b (encoding for the FcγRIIB receptor), we investigated whether the IRF5/Blimp-1 axis could regulate the expression of these genes. We found that an Irf5 deficiency in mice decreased the expression of Blimp-1 and reduced the expression of the Ifi202. However, the deficiency increased the expression of Aim2 and Fcgr2b. Correspondingly, increased expression of IRF5 in cells increased levels of Blimp-1 and p202 protein. Moreover, Blimp-1 expression increased the expression of Ifi202, whereas it reduced the expression of Aim2. Interestingly, an Aim2 deficiency in female mice increased the expression of IRF5. Similarly, the Fcgr2b-deficient mice expressed increased levels of IRF5. Moreover, increased expression of IRF5 and Blimp-1 in lupus-prone C57BL/6.Nba2, New Zealand Black, and C57BL/6.Sle123 female mice (as compared with age-matched C57BL/6 female mice) was associated with increased levels of the p202 protein. Taken together, our observations demonstrate that the IRF5/Blimp-1 axis differentially regulates the expression of Nba2 lupus susceptibility genes, and they suggest an important role for the IRF5/Blimp-1/p202 axis in murine lupus susceptibility.