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1.
J Exp Med ; 220(12)2023 12 04.
Artigo em Inglês | MEDLINE | ID: mdl-37773045

RESUMO

Central B cell tolerance is believed to be regulated by B cell receptor signaling induced by the recognition of self-antigens in immature B cells. Using humanized mice with defective MyD88, TLR7, or TLR9 expression, we demonstrate that TLR9/MYD88 are required for central B cell tolerance and the removal of developing autoreactive clones. We also show that CXCL4, a chemokine involved in systemic sclerosis (SSc), abrogates TLR9 function in B cells by sequestering TLR9 ligands away from the endosomal compartments where this receptor resides. The in vivo production of CXCL4 thereby impedes both TLR9 responses in B cells and the establishment of central B cell tolerance. We conclude that TLR9 plays an essential early tolerogenic function required for the establishment of central B cell tolerance and that correcting defective TLR9 function in B cells from SSc patients may represent a novel therapeutic strategy to restore B cell tolerance.


Assuntos
Fator Plaquetário 4 , Escleroderma Sistêmico , Receptor Toll-Like 9 , Animais , Humanos , Camundongos , Linfócitos B , Ligantes , Fator 88 de Diferenciação Mieloide/metabolismo , Fator Plaquetário 4/metabolismo , Escleroderma Sistêmico/metabolismo , Receptor 7 Toll-Like , Receptor Toll-Like 9/metabolismo
3.
J Clin Invest ; 130(8): 4411-4422, 2020 08 03.
Artigo em Inglês | MEDLINE | ID: mdl-32484799

RESUMO

Patients with common variable immunodeficiency associated with autoimmune cytopenia (CVID+AIC) generate few isotype-switched B cells with severely decreased frequencies of somatic hypermutations (SHMs), but their underlying molecular defects remain poorly characterized. We identified a CVID+AIC patient who displays a rare homozygous missense M466V mutation in ß-catenin-like protein 1 (CTNNBL1). Because CTNNBL1 binds activation-induced cytidine deaminase (AID) that catalyzes SHM, we tested AID interactions with the CTNNBL1 M466V variant. We found that the M466V mutation interfered with the association of CTNNBL1 with AID, resulting in decreased AID in the nuclei of patient EBV-transformed B cell lines and of CTNNBL1 466V/V Ramos B cells engineered to express only CTNNBL1 M466V using CRISPR/Cas9 technology. As a consequence, the scarce IgG+ memory B cells from the CTNNBL1 466V/V patient showed a low SHM frequency that averaged 6.7 mutations compared with about 18 mutations per clone in healthy-donor counterparts. In addition, CTNNBL1 466V/V Ramos B cells displayed a decreased incidence of SHM that was reduced by half compared with parental WT Ramos B cells, demonstrating that the CTNNBL1 M466V mutation is responsible for defective SHM induction. We conclude that CTNNBL1 plays an important role in regulating AID-dependent antibody diversification in humans.


Assuntos
Proteínas Reguladoras de Apoptose , Linfócitos B , Imunodeficiência de Variável Comum , Homozigoto , Memória Imunológica/genética , Mutação de Sentido Incorreto , Proteínas Nucleares , Hipermutação Somática de Imunoglobulina , Substituição de Aminoácidos , Proteínas Reguladoras de Apoptose/genética , Proteínas Reguladoras de Apoptose/imunologia , Linfócitos B/imunologia , Linfócitos B/patologia , Linhagem Celular , Pré-Escolar , Imunodeficiência de Variável Comum/genética , Imunodeficiência de Variável Comum/imunologia , Imunodeficiência de Variável Comum/patologia , Citidina Desaminase/genética , Citidina Desaminase/imunologia , Feminino , Humanos , Proteínas Nucleares/genética , Proteínas Nucleares/imunologia
4.
Sci Transl Med ; 11(519)2019 11 20.
Artigo em Inglês | MEDLINE | ID: mdl-31748230

RESUMO

Patients with rheumatoid arthritis (RA) may display atypical CD21-/lo B cells in their blood, but the implication of this observation remains unclear. We report here that the group of patients with RA and elevated frequencies of CD21-/lo B cells shows decreased ataxia telangiectasia-mutated (ATM) expression and activation in B cells compared with other patients with RA and healthy donor controls. In agreement with ATM involvement in the regulation of V(D)J recombination, patients with RA who show defective ATM function displayed a skewed B cell receptor (BCR) Igκ repertoire, which resembled that of patients with ataxia telangiectasia (AT). This repertoire was characterized by increased Jκ1 and decreased upstream Vκ gene segment usage, suggesting improper secondary recombination processes and selection. In addition, altered ATM function in B cells was associated with decreased osteoprotegerin and increased receptor activator of nuclear factor κB ligand (RANKL) production. These changes favor bone loss and correlated with a higher prevalence of erosive disease in patients with RA who show impaired ATM function. Using a humanized mouse model, we also show that ATM inhibition in vivo induces an altered Igκ repertoire and RANKL production by immature B cells in the bone marrow, leading to decreased bone density. We conclude that dysregulated ATM function in B cells promotes bone erosion and the emergence of circulating CD21-/lo B cells, thereby contributing to RA pathophysiology.


Assuntos
Artrite Reumatoide/imunologia , Proteínas Mutadas de Ataxia Telangiectasia/metabolismo , Linfócitos B/metabolismo , Reabsorção Óssea/imunologia , Animais , Artrite Reumatoide/fisiopatologia , Proteínas Mutadas de Ataxia Telangiectasia/antagonistas & inibidores , Densidade Óssea , Reabsorção Óssea/fisiopatologia , Sobrevivência Celular/imunologia , Humanos , Imunoglobulinas/imunologia , Articulações/patologia , Contagem de Linfócitos , Camundongos , Pessoa de Meia-Idade , Osteogênese , Osteoprotegerina/metabolismo , Fenótipo , Ligante RANK/metabolismo , Receptores de Complemento 3d/metabolismo , Recombinação Genética/genética
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