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1.
PLoS Genet ; 15(6): e1007721, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-31199803

RESUMO

B-cell activation yields abundant cell death in parallel to clonal amplification and remodeling of immunoglobulin (Ig) genes by activation-induced deaminase (AID). AID promotes affinity maturation of Ig variable regions and class switch recombination (CSR) in mature B lymphocytes. In the IgH locus, these processes are under control of the 3' regulatory region (3'RR) super-enhancer, a region demonstrated in the mouse to be both transcribed and itself targeted by AID-mediated recombination. Alternatively to CSR, IgH deletions joining Sµ to "like-switch" DNA repeats that flank the 3' super-enhancer can thus accomplish so-called "locus suicide recombination" (LSR) in mouse B-cells. Using an optimized LSR-seq high throughput method, we now show that AID-mediated LSR is evolutionarily conserved and also actively occurs in humans, providing an activation-induced cell death pathway in multiple conditions of B-cell activation. LSR either focuses on the functional IgH allele or is bi-allelic, and its signature is mainly detected when LSR is ongoing while it vanishes from fully differentiated plasma cells or from "resting" blood memory B-cells. Highly diversified breakpoints are distributed either within the upstream (3'RR1) or downstream (3'RR2) copies of the IgH 3' super-enhancer and all conditions activating CSR in vitro also seem to trigger LSR although TLR ligation appeared the most efficient. Molecular analysis of breakpoints and junctions confirms that LSR is AID-dependent and reveals junctional sequences somehow similar to CSR junctions but with increased usage of microhomologies.


Assuntos
Linfócitos B/imunologia , Citidina Desaminase/genética , Região de Troca de Imunoglobulinas/genética , Imunoglobulinas/imunologia , Alelos , Animais , Diferenciação Celular/genética , Citidina Desaminase/imunologia , Marcação de Genes , Humanos , Região de Troca de Imunoglobulinas/imunologia , Tecido Linfoide/imunologia , Camundongos , Tonsila Palatina/imunologia , Tonsila Palatina/metabolismo , Plasmócitos/imunologia , Plasmócitos/metabolismo , Receptores de Antígenos de Linfócitos B/genética , Receptores de Antígenos de Linfócitos B/imunologia , Sequências Reguladoras de Ácido Nucleico
2.
Sci Rep ; 9(1): 3109, 2019 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-30816165

RESUMO

Human cells are stressed by numerous mechanisms that can lead to leakage of mitochondrial DNA (mtDNA) to the cytoplasm and ultimately apoptosis. This agonist DNA constitutes a danger to the cell and is counteracted by cytoplasmic DNases and APOBEC3 cytidine deamination of DNA. To investigate APOBEC3 editing of leaked mtDNA to the cytoplasm, we performed a PCR analysis of APOBEC3 edited cytoplasmic mtDNA (cymtDNA) at the single cell level for primary CD4+ T cells and the established P2 EBV blast cell line. Up to 17% of primary CD4+ T cells showed signs of APOBEC3 edited cymtDNA with ~50% of all mtDNA sequences showing signs of APOBEC3 editing - between 1500-5000 molecules. Although the P2 cell line showed a much lower frequency of stressed cells, the number of edited mtDNA molecules in such cells was of the same order. Addition of the genotoxic molecules, etoposide or actinomycin D increased the number of cells showing APOBEC3 edited cymtDNA to around 40%. These findings reveal a very dynamic image of the mitochondrial network, which changes considerably under stress. APOBEC3 deaminases are involved in the catabolism of mitochondrial DNA to circumvent chronic immune stimulation triggered by released mitochondrial DNA from damaged cells.

3.
J Clin Invest ; 2018 Dec 06.
Artigo em Inglês | MEDLINE | ID: mdl-30521495

RESUMO

ARHGEF1 is a RhoA-specific guanine nucleotide exchange factor expressed in hematopoietic cells. We used whole-exome sequencing to identify compound heterozygous mutations in ARHGEF1, resulting in the loss of ARHGEF1 protein expression in two primary-antibody-deficient siblings presenting with recurrent severe respiratory tract infections and bronchiectasis. Both ARHGEF1-deficient patients showed an abnormal B cell immunophenotype, with a deficiency in marginal-zone and memory B cells and an increased frequency of transitional B cells. Furthermore, the patients' blood contained immature myeloid cells. Analysis of a mediastinal lymph node from one patient highlighted the small size of the germinal centres and an abnormally high plasma cell content. On the molecular level, T and B lymphocytes from both patients displayed low RhoA activity and low steady-state actin polymerization (even after stimulation of lysophospholipid receptors). As a consequence of disturbed regulation of the RhoA downstream target ROCK, the patients' lymphocytes failed to efficiently restrain AKT phosphorylation. Enforced ARHGEF1 expression or drug-induced activation of RhoA in patients' cells corrected the impaired actin polymerization and AKT regulation. Our results indicate that ARHGEF1 activity in human lymphocytes is involved in controlling actin cytoskeleton dynamics, restraining PI3K/AKT signalling, and confining B lymphocytes and myelocytes within their dedicated functional environment.

4.
Artigo em Inglês | MEDLINE | ID: mdl-29778502

RESUMO

BACKGROUND: Activated phosphatidylinositol-3-OH kinase δ syndrome type 1 (APDS1) is a recently described primary immunodeficiency syndrome characterized by recurrent respiratory tract infections, lymphoid hyperplasia, and Herpesviridae infections caused by germline gain-of-function mutations of PIK3CD. Hematopoietic stem cell transplantation (HSCT) can be considered to ameliorate progressive immunodeficiency and associated malignancy, but appropriate indications, methods, and outcomes of HSCT for APDS1 remain undefined. OBJECTIVE: Our objective was to analyze the clinical manifestations, laboratory findings, prognosis, and treatment of APDS1 and explore appropriate indications and methods of HSCT. METHODS: We reviewed retrospectively the medical records of cohorts undergoing HSCT at collaborating facilities. RESULTS: Thirty-year overall survival was 86.1%, but event-free survival was 39.6%. Life-threatening events, such as severe infections or lymphoproliferation, were frequent in childhood and adolescence and were common indications for HSCT. Nine patients underwent HSCT with fludarabine-based reduced-intensity conditioning. Seven patients survived after frequent adverse complications and engraftment failure. Most symptoms improved after HSCT. CONCLUSION: Patients with APDS1 showed variable clinical manifestations. Life-threatening progressive combined immunodeficiency and massive lymphoproliferation were common indications for HSCT. Fludarabine-based reduced-intensity conditioning-HSCT ameliorated clinical symptoms, but transplantation-related complications were frequent, including graft failure.

6.
J Allergy Clin Immunol ; 139(2): 597-606.e4, 2017 02.
Artigo em Inglês | MEDLINE | ID: mdl-27555459

RESUMO

BACKGROUND: Activated phosphoinositide 3-kinase δ syndrome (APDS) is a recently described combined immunodeficiency resulting from gain-of-function mutations in PIK3CD, the gene encoding the catalytic subunit of phosphoinositide 3-kinase δ (PI3Kδ). OBJECTIVE: We sought to review the clinical, immunologic, histopathologic, and radiologic features of APDS in a large genetically defined international cohort. METHODS: We applied a clinical questionnaire and performed review of medical notes, radiology, histopathology, and laboratory investigations of 53 patients with APDS. RESULTS: Recurrent sinopulmonary infections (98%) and nonneoplastic lymphoproliferation (75%) were common, often from childhood. Other significant complications included herpesvirus infections (49%), autoinflammatory disease (34%), and lymphoma (13%). Unexpectedly, neurodevelopmental delay occurred in 19% of the cohort, suggesting a role for PI3Kδ in the central nervous system; consistent with this, PI3Kδ is broadly expressed in the developing murine central nervous system. Thoracic imaging revealed high rates of mosaic attenuation (90%) and bronchiectasis (60%). Increased IgM levels (78%), IgG deficiency (43%), and CD4 lymphopenia (84%) were significant immunologic features. No immunologic marker reliably predicted clinical severity, which ranged from asymptomatic to death in early childhood. The majority of patients received immunoglobulin replacement and antibiotic prophylaxis, and 5 patients underwent hematopoietic stem cell transplantation. Five patients died from complications of APDS. CONCLUSION: APDS is a combined immunodeficiency with multiple clinical manifestations, many with incomplete penetrance and others with variable expressivity. The severity of complications in some patients supports consideration of hematopoietic stem cell transplantation for severe childhood disease. Clinical trials of selective PI3Kδ inhibitors offer new prospects for APDS treatment.


Assuntos
Classe I de Fosfatidilinositol 3-Quinases/genética , Síndromes de Imunodeficiência/genética , Transtornos Linfoproliferativos/genética , Mutação/genética , Infecções Respiratórias/genética , Adolescente , Adulto , Animais , Antibioticoprofilaxia , Criança , Pré-Escolar , Classe I de Fosfatidilinositol 3-Quinases/antagonistas & inibidores , Estudos de Coortes , Inibidores Enzimáticos/uso terapêutico , Feminino , Transplante de Células-Tronco Hematopoéticas , Infecções por Herpesviridae/genética , Infecções por Herpesviridae/mortalidade , Infecções por Herpesviridae/terapia , Humanos , Imunoglobulinas Intravenosas/uso terapêutico , Síndromes de Imunodeficiência/mortalidade , Síndromes de Imunodeficiência/terapia , Lactente , Cooperação Internacional , Transtornos Linfoproliferativos/mortalidade , Transtornos Linfoproliferativos/terapia , Masculino , Camundongos , Pessoa de Meia-Idade , Recidiva , Infecções Respiratórias/mortalidade , Infecções Respiratórias/terapia , Inquéritos e Questionários , Análise de Sobrevida , Adulto Jovem
7.
J Clin Invest ; 126(11): 4289-4302, 2016 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-27701145

RESUMO

Patients with mutations in AICDA, which encodes activation-induced cytidine deaminase (AID), display an impaired peripheral B cell tolerance. AID mediates class-switch recombination (CSR) and somatic hypermutation (SHM) in B cells, but the mechanism by which AID prevents the accumulation of autoreactive B cells in blood is unclear. Here, we analyzed B cell tolerance in AID-deficient patients, patients with autosomal dominant AID mutations (AD-AID), asymptomatic AICDA heterozygotes (AID+/-), and patients with uracil N-glycosylase (UNG) deficiency, which impairs CSR but not SHM. The low frequency of autoreactive mature naive B cells in UNG-deficient patients resembled that of healthy subjects, revealing that impaired CSR does not interfere with the peripheral B cell tolerance checkpoint. In contrast, we observed decreased frequencies of SHM in memory B cells from AD-AID patients and AID+/- subjects, who were unable to prevent the accumulation of autoreactive mature naive B cells. In addition, the individuals with AICDA mutations, but not UNG-deficient patients, displayed Tregs with defective suppressive capacity that correlated with increases in circulating T follicular helper cells and enhanced cytokine production. We conclude that SHM, but not CSR, regulates peripheral B cell tolerance through the production of mutated antibodies that clear antigens and prevent sustained interleukin secretions that interfere with Treg function.


Assuntos
Linfócitos B/imunologia , Pontos de Checagem do Ciclo Celular/imunologia , Citidina Desaminase/deficiência , Tolerância Imunológica , Memória Imunológica , Mutação , Hipermutação Somática de Imunoglobulina/imunologia , Linfócitos B/patologia , Pontos de Checagem do Ciclo Celular/genética , Citidina Desaminase/imunologia , Feminino , Humanos , Masculino , Linfócitos T Reguladores/imunologia , Linfócitos T Reguladores/patologia
8.
J Allergy Clin Immunol ; 138(6): 1681-1689.e8, 2016 12.
Artigo em Inglês | MEDLINE | ID: mdl-27405666

RESUMO

BACKGROUND: We investigated 7 male patients (from 5 different families) presenting with profound lymphopenia, hypogammaglobulinemia, fluctuating monocytopenia and neutropenia, a poor immune response to vaccine antigens, and increased susceptibility to bacterial and varicella zoster virus infections. OBJECTIVE: We sought to characterize the genetic defect involved in a new form of X-linked immunodeficiency. METHODS: We performed genetic analyses and an exhaustive phenotypic and functional characterization of the lymphocyte compartment. RESULTS: We observed hemizygous mutations in the moesin (MSN) gene (located on the X chromosome and coding for MSN) in all 7 patients. Six of the latter had the same missense mutation, which led to an amino acid substitution (R171W) in the MSN four-point-one, ezrin, radixin, moesin domain. The seventh patient had a nonsense mutation leading to a premature stop codon mutation (R533X). The naive T-cell counts were particularly low for age, and most CD8+ T cells expressed the senescence marker CD57. This phenotype was associated with impaired T-cell proliferation, which was rescued by expression of wild-type MSN. MSN-deficient T cells also displayed poor chemokine receptor expression, increased adhesion molecule expression, and altered migration and adhesion capacities. CONCLUSION: Our observations establish a causal link between an ezrin-radixin-moesin protein mutation and a primary immunodeficiency that could be referred to as X-linked moesin-associated immunodeficiency.


Assuntos
Linfócitos T CD8-Positivos/imunologia , Cromossomos Humanos X/genética , Síndromes de Imunodeficiência/genética , Infecção/genética , Proteínas dos Microfilamentos/genética , Mutação/genética , Adolescente , Adulto , Idoso , Adesão Celular , Movimento Celular , Criança , Pré-Escolar , Estudos de Associação Genética , Humanos , Contagem de Linfócitos , Masculino , Linhagem
10.
J Allergy Clin Immunol ; 138(1): 210-218.e9, 2016 07.
Artigo em Inglês | MEDLINE | ID: mdl-27221134

RESUMO

BACKGROUND: Activated phosphoinositide 3-kinase δ syndrome (APDS) 2 (p110δ-activating mutations causing senescent T cells, lymphadenopathy, and immunodeficiency [PASLI]-R1), a recently described primary immunodeficiency, results from autosomal dominant mutations in PIK3R1, the gene encoding the regulatory subunit (p85α, p55α, and p50α) of class IA phosphoinositide 3-kinases. OBJECTIVES: We sought to review the clinical, immunologic, and histopathologic phenotypes of APDS2 in a genetically defined international patient cohort. METHODS: The medical and biological records of 36 patients with genetically diagnosed APDS2 were collected and reviewed. RESULTS: Mutations within splice acceptor and donor sites of exon 11 of the PIK3R1 gene lead to APDS2. Recurrent upper respiratory tract infections (100%), pneumonitis (71%), and chronic lymphoproliferation (89%, including adenopathy [75%], splenomegaly [43%], and upper respiratory tract lymphoid hyperplasia [48%]) were the most common features. Growth retardation was frequently noticed (45%). Other complications were mild neurodevelopmental delay (31%); malignant diseases (28%), most of them being B-cell lymphomas; autoimmunity (17%); bronchiectasis (18%); and chronic diarrhea (24%). Decreased serum IgA and IgG levels (87%), increased IgM levels (58%), B-cell lymphopenia (88%) associated with an increased frequency of transitional B cells (93%), and decreased numbers of naive CD4 and naive CD8 cells but increased numbers of CD8 effector/memory T cells were predominant immunologic features. The majority of patients (89%) received immunoglobulin replacement; 3 patients were treated with rituximab, and 6 were treated with rapamycin initiated after diagnosis of APDS2. Five patients died from APDS2-related complications. CONCLUSION: APDS2 is a combined immunodeficiency with a variable clinical phenotype. Complications are frequent, such as severe bacterial and viral infections, lymphoproliferation, and lymphoma similar to APDS1/PASLI-CD. Immunoglobulin replacement therapy, rapamycin, and, likely in the near future, selective phosphoinositide 3-kinase δ inhibitors are possible treatment options.


Assuntos
Classe I de Fosfatidilinositol 3-Quinases/genética , Síndromes de Imunodeficiência/diagnóstico , Síndromes de Imunodeficiência/etiologia , Fenótipo , Adolescente , Adulto , Alelos , Biópsia , Linfócitos T CD8-Positivos/imunologia , Linfócitos T CD8-Positivos/metabolismo , Criança , Pré-Escolar , Estudos de Coortes , Feminino , Frequência do Gene , Genótipo , Humanos , Síndromes de Imunodeficiência/mortalidade , Masculino , Pessoa de Meia-Idade , Mutação , Sítios de Splice de RNA , Subpopulações de Linfócitos T/imunologia , Subpopulações de Linfócitos T/metabolismo , Adulto Jovem
11.
Immunity ; 43(5): 884-95, 2015 Nov 17.
Artigo em Inglês | MEDLINE | ID: mdl-26546282

RESUMO

Activation-induced cytidine deaminase (AID), the enzyme-mediating class-switch recombination (CSR) and somatic hypermutation (SHM) of immunoglobulin genes, is essential for the removal of developing autoreactive B cells. How AID mediates central B cell tolerance remains unknown. We report that AID enzymes were produced in a discrete population of immature B cells that expressed recombination-activating gene 2 (RAG2), suggesting that they undergo secondary recombination to edit autoreactive antibodies. However, most AID+ immature B cells lacked anti-apoptotic MCL-1 and were deleted by apoptosis. AID inhibition using lentiviral-encoded short hairpin (sh)RNA in B cells developing in humanized mice resulted in a failure to remove autoreactive clones. Hence, B cell intrinsic AID expression mediates central B cell tolerance potentially through its RAG-coupled genotoxic activity in self-reactive immature B cells.


Assuntos
Tolerância Central/genética , Tolerância Central/imunologia , Citidina Desaminase/genética , Ativação Linfocitária/imunologia , Células Precursoras de Linfócitos B/imunologia , Adolescente , Adulto , Idoso , Animais , Apoptose/genética , Apoptose/imunologia , Estudos de Casos e Controles , Criança , Pré-Escolar , Proteínas de Ligação a DNA/genética , Feminino , Genes de Imunoglobulinas/genética , Genes de Imunoglobulinas/imunologia , Humanos , Ativação Linfocitária/genética , Masculino , Camundongos , Pessoa de Meia-Idade , Proteínas Nucleares/genética , Recombinação Genética/genética , Recombinação Genética/imunologia , Hipermutação Somática de Imunoglobulina/genética , Hipermutação Somática de Imunoglobulina/imunologia , Adulto Jovem
15.
J Med Genet ; 52(5): 348-52, 2015 May.
Artigo em Inglês | MEDLINE | ID: mdl-25691505

RESUMO

BACKGROUND: Inherited mutations in DNA mismatch repair genes predispose to different cancer syndromes depending on whether they are mono-allelic or bi-allelic. This supports a causal relationship between expression level in the germline and phenotype variation. As a model to study this relationship, our study aimed to define the pathogenic characteristics of a recurrent homozygous coding variant in PMS2 displaying an attenuated phenotype identified by clinical genetic testing in seven Inuit families from Northern Quebec. METHODS: Pathogenic characteristics of the PMS2 mutation NM_000535.5:c.2002A>G were studied using genotype-phenotype correlation, single-molecule expression detection and single genome microsatellite instability analysis. RESULTS: This PMS2 mutation generates a de novo splice site that competes with the authentic site. In homozygotes, expression of the full-length protein is reduced to a level barely detectable by conventional diagnostics. Median age at primary cancer diagnosis is 22 years among 13 NM_000535.5:c.2002A>G homozygotes, versus 8 years in individuals carrying bi-allelic truncating mutations. Residual expression of full-length PMS2 transcript was detected in normal tissues from homozygotes with cancers in their 20s. CONCLUSIONS: Our genotype-phenotype study of c.2002A>G illustrates that an extremely low level of PMS2 expression likely delays cancer onset, a feature that could be exploited in cancer preventive intervention.


Assuntos
Adenosina Trifosfatases/genética , Neoplasias Encefálicas/diagnóstico , Neoplasias Encefálicas/genética , Neoplasias Colorretais/diagnóstico , Neoplasias Colorretais/genética , Enzimas Reparadoras do DNA/genética , Proteínas de Ligação a DNA/genética , Efeito Fundador , Homozigoto , Mutação , Síndromes Neoplásicas Hereditárias/diagnóstico , Síndromes Neoplásicas Hereditárias/genética , Fenótipo , Adolescente , Adulto , Idoso , Alelos , Criança , Pré-Escolar , Mapeamento Cromossômico , Éxons , Feminino , Expressão Gênica , Estudos de Associação Genética , Humanos , Lactente , Masculino , Pessoa de Meia-Idade , Endonuclease PMS2 de Reparo de Erro de Pareamento , Adulto Jovem
16.
J Allergy Clin Immunol ; 135(4): 998-1007.e6, 2015 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-25312759

RESUMO

BACKGROUND: Immunoglobulin class-switch recombination defects (CSR-D) are rare primary immunodeficiencies characterized by impaired production of switched immunoglobulin isotypes and normal or elevated IgM levels. They are caused by impaired T:B cooperation or intrinsic B cell defects. However, many immunoglobulin CSR-Ds are still undefined at the molecular level. OBJECTIVE: This study's objective was to delineate new causes of immunoglobulin CSR-Ds and thus gain further insights into the process of immunoglobulin class-switch recombination (CSR). METHODS: Exome sequencing in 2 immunoglobulin CSR-D patients identified variations in the INO80 gene. Functional experiments were performed to assess the function of INO80 on immunoglobulin CSR. RESULTS: We identified recessive, nonsynonymous coding variations in the INO80 gene in 2 patients affected by defective immunoglobulin CSR. Expression of wild-type INO80 in patients' fibroblastic cells corrected their hypersensitivity to high doses of γ-irradiation. In murine CH12-F3 cells, the INO80 complex accumulates at Sα and Eµ regions of the IgH locus, and downregulation of INO80 as well as its partners Reptin and Pontin impaired CSR. In addition, Reptin and Pontin were shown to interact with activation-induced cytidine deaminase. Finally, an abnormal separation of sister chromatids was observed upon INO80 downregulation in CH12-F3 cells, pinpointing its role in cohesin activity. CONCLUSION: INO80 deficiency appears to be associated with defective immunoglobulin CSR. We propose that the INO80 complex modulates cohesin function that may be required during immunoglobulin switch region synapsis.


Assuntos
Montagem e Desmontagem da Cromatina , DNA Helicases/genética , Rearranjo Gênico , Switching de Imunoglobulina , Síndromes de Imunodeficiência/genética , Síndromes de Imunodeficiência/imunologia , ATPases Associadas a Diversas Atividades Celulares , Proteínas de Transporte/metabolismo , Proteínas de Ciclo Celular/metabolismo , Linhagem Celular , Sobrevivência Celular/genética , Proteínas Cromossômicas não Histona/metabolismo , DNA Helicases/metabolismo , Reparo do DNA , Regulação da Expressão Gênica , Variação Genética , Humanos , Isotipos de Imunoglobulinas/genética , Região de Troca de Imunoglobulinas , Síndromes de Imunodeficiência/metabolismo , Modelos Biológicos , Ligação Proteica , Transporte Proteico
17.
J Immunoassay Immunochem ; 36(1): 16-26, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-24568663

RESUMO

Ataxia telangiectasia (AT) is a rare primary immunodeficiency disorder with various clinical manifestations. Increased serum levels of IgM and recurrent infections, mainly sinopulmonary infections, can be the presenting feature in a number of AT patients and may be initially misdiagnosed as hyper-IgM (HIgM) syndrome. This study was designed to investigate class switch recombination (CSR) as a critical mechanism in B lymphocytes' maturation to produce different isotypes of antibody in response to antigen stimulation in AT cases with HIgM presentation. Quantitative IgE production after stimulation by IL-4 and CD40L was considered as an indicator for CSR function. We also compared their results with sex and age matched AT patients without HIgM presentation. We report four AT patients with recurrent infections during infancy and high serum levels of IgM. Laboratory evaluations revealed defective CSR while none of the three AT patients without HIgM presentation had a defect in the CSR process. The characterized defect in AT is a mutation in the ataxia telangiectasia mutated (ATM) gene. This gene may result in CSR defects due to impaired DNA break repair. A special association between AT and HIgM may indicate a new subgroup of AT patients according to their clinical phenotype and CSR condition.


Assuntos
Ataxia Telangiectasia/imunologia , Switching de Imunoglobulina/imunologia , Imunoglobulina M/sangue , Recombinação Genética/imunologia , Ataxia Telangiectasia/genética , Humanos , Switching de Imunoglobulina/genética , Imunoglobulina M/imunologia , Mutação , Recombinação Genética/genética
18.
J Allergy Clin Immunol ; 134(2): 276-84, 2014 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-25087226

RESUMO

Next-generation DNA sequencing has accelerated the genetic characterization of many human primary immunodeficiency diseases (PIDs). These discoveries can be lifesaving for the affected patients and also provide a unique opportunity to study the effect of specific genes on human immune function. In the past 18 months, a number of independent groups have begun to define novel PIDs caused by defects in the caspase recruitment domain family, member 11 (CARD11)-B-cell chronic lymphocytic leukemia/lymphoma 10 (BCL10)-mucosa-associated lymphoid tissue lymphoma translocation gene 1 (MALT1 [CBM]) signalosome complex. The CBM complex forms an essential molecular link between the triggering of cell-surface antigen receptors and nuclear factor κB activation. Germline mutations affecting the CBM complex are now recognized as the cause of novel combined immunodeficiency phenotypes, which all share abnormal nuclear factor κB activation and dysregulated B-cell development as defining features. For this "Current perspectives" article, we have engaged experts in both basic biology and clinical immunology to capture the worldwide experience in recognizing and managing patients with PIDs caused by CBM complex mutations.


Assuntos
Proteínas Adaptadoras de Transdução de Sinal/genética , Linfócitos B/patologia , Proteínas Adaptadoras de Sinalização CARD/genética , Caspases/genética , Guanilato Ciclase/genética , Síndromes de Imunodeficiência/genética , Proteínas de Neoplasias/genética , Proteínas Adaptadoras de Transdução de Sinal/imunologia , Proteína 10 de Linfoma CCL de Células B , Linfócitos B/imunologia , Proteínas Adaptadoras de Sinalização CARD/imunologia , Caspases/imunologia , Regulação da Expressão Gênica , Mutação em Linhagem Germinativa , Guanilato Ciclase/imunologia , Sequenciamento de Nucleotídeos em Larga Escala , Humanos , Síndromes de Imunodeficiência/diagnóstico , Síndromes de Imunodeficiência/imunologia , Síndromes de Imunodeficiência/patologia , Proteína de Translocação 1 do Linfoma de Tecido Linfoide Associado à Mucosa , NF-kappa B/genética , NF-kappa B/imunologia , Proteínas de Neoplasias/imunologia , Receptores de Antígenos de Linfócitos B/genética , Receptores de Antígenos de Linfócitos B/imunologia , Transdução de Sinais
19.
J Clin Invest ; 124(9): 3923-8, 2014 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-25133428

RESUMO

Recently, patient mutations that activate PI3K signaling have been linked to a primary antibody deficiency. Here, we used whole-exome sequencing and characterized the molecular defects in 4 patients from 3 unrelated families diagnosed with hypogammaglobulinemia and recurrent infections. We identified 2 different heterozygous splice site mutations that affect the same splice site in PIK3R1, which encodes the p85α subunit of PI3K. The resulting deletion of exon 10 produced a shortened p85α protein that lacks part of the PI3K p110-binding domain. The hypothetical loss of p85α-mediated inhibition of p110 activity was supported by elevated phosphorylation of the known downstream signaling kinase AKT in patient T cell blasts. Analysis of patient blood revealed that naive T and memory B cell counts were low, and T cell blasts displayed enhanced activation-induced cell death, which was corrected by addition of the PI3Kδ inhibitor IC87114. Furthermore, B lymphocytes proliferated weakly in response to activation via the B cell receptor and TLR9, indicating a B cell defect. The phenotype exhibited by patients carrying the PIK3R1 splice site mutation is similar to that of patients carrying gain-of-function mutations in PIK3CD. Our results suggest that PI3K activity is tightly regulated in T and B lymphocytes and that various defects in the PI3K-triggered pathway can cause primary immunodeficiencies.


Assuntos
Síndromes de Imunodeficiência/genética , Mutação , Fosfatidilinositol 3-Quinases/genética , Feminino , Humanos , Lactente , Ativação Linfocitária , Masculino , PTEN Fosfo-Hidrolase/fisiologia , Fosfatidilinositol 3-Quinases/fisiologia , Fosforilação , Proteínas Proto-Oncogênicas c-akt/metabolismo , Transdução de Sinais
20.
Blood ; 124(10): 1597-609, 2014 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-24970930

RESUMO

Autoimmune lymphoproliferative syndrome (ALPS) caused by impaired FAS-mediated apoptosis of lymphocytes is characterized by lymphoproliferation, autoimmunity, but also an increased risk of invasive bacterial infection, notably following splenectomy. We surveyed a cohort of 100 ALPS patients (including 33 splenectomized) and found that 12 (10 splenectomized) had experienced 23 invasive bacterial infections mainly caused by Streptococcus pneumoniae. This vulnerability was associated with evidence of defective B-cell function characterized by low serum immunoglobulin (Ig) M, low IgM antibody production in response to S pneumoniae following nonconjugated immunization, and low blood memory B-cells counts (including marginal zone [MZ] B-cell counts). This immunodeficiency strongly correlated with intensity of lymphoproliferation. Spleen sections from 9 ALPS patients revealed double-negative T-cell (DN-T) infiltration of the MZ, which was depleted of B cells. MZ in ALPS patients contained an abnormally thick layer of MAdCAM-1((+)) stromal cells and an excess of DN-Ts. DN-Ts were shown to express MAdCAM-1 ligand, the α4ß7 integrin. These observations suggest that accumulating DN-Ts are trapped within stromal cell meshwork and interfere with correct localization of MZ B cells. Similar observations were made in spleens of fas-deficient mice. Our data revealed an unexpected mechanism by which ALPS results in anti-polysaccharide IgM antibody production-specific defect. Splenectomy should be avoided.


Assuntos
Formação de Anticorpos , Síndrome Linfoproliferativa Autoimune/imunologia , Síndrome Linfoproliferativa Autoimune/patologia , Lipopolissacarídeos/imunologia , Baço/imunologia , Baço/patologia , Adolescente , Adulto , Animais , Síndrome Linfoproliferativa Autoimune/epidemiologia , Síndrome Linfoproliferativa Autoimune/cirurgia , Criança , Pré-Escolar , Humanos , Lactente , Recém-Nascido , Camundongos , Camundongos Transgênicos , Baço/cirurgia , Esplenectomia/efeitos adversos , Esplenectomia/estatística & dados numéricos , Infecções Estreptocócicas/epidemiologia , Infecções Estreptocócicas/imunologia , Streptococcus pneumoniae/crescimento & desenvolvimento , Streptococcus pneumoniae/imunologia , Adulto Jovem
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