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Blockade of B-cell-activating factor suppresses lupus-like syndrome in autoimmune BXSB mice.

ABSTRACT: B-cell-activating factor (BAFF), a member of the tumour necrosis factor superfamily, plays a critical role in the maturation, homeostasis and function of B cells. In this study, we demonstrated the biological outcome of BAFF blockade in BXSB murine lupus model, using a soluble fusion protein consisting of human BAFF-R and human mutant IgG4 Fc. Mutation of Leu(235) to Glu in IgG4 Fc eliminated antibody-dependent cell cytotoxicity (ADCC) and complement lysis activity, and generated a protein devoid of immune effector functions. Treatment of BXSB mice with BAFF-R-IgG4mut fusion protein for 5 weeks resulted in significant B-cell reduction in both the peripheral blood and spleen. Treated mice developed lower proteinuria, reduced glomerulonephritis and much delayed host death than untreated animals. Thus, BAFF blockade with BAFF-R-IgG4mut protein is an effective strategy to treat B-cell-mediated lupus-like pathology. Moreover, compared with other IgG isotypes with undesired effector functions, mutant IgG4 Fc should prove useful in constructing novel therapeutic reagents to block immune molecule signalling in various diseases.

SUBMITTER: Ding H

PROVIDER: S-EPMC3829033 | biostudies-literature | 2010 Jun

REPOSITORIES: biostudies-literature

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Blockade of B-cell-activating factor suppresses lupus-like syndrome in autoimmune BXSB mice.

Ding Hanlu H Wang Li L Wu Xiongfei X Yan Jun J He Yani Y Ni Bing B Gao Wenda W Zhong Xuemei X

Journal of cellular and molecular medicine 20090720 6B

B-cell-activating factor (BAFF), a member of the tumour necrosis factor superfamily, plays a critical role in the maturation, homeostasis and function of B cells. In this study, we demonstrated the biological outcome of BAFF blockade in BXSB murine lupus model, using a soluble fusion protein consisting of human BAFF-R and human mutant IgG4 Fc. Mutation of Leu(235) to Glu in IgG4 Fc eliminated antibody-dependent cell cytotoxicity (ADCC) and complement lysis activity, and generated a protein devoi ...[more]

PMID: 19627403

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Project description:Occupational exposure to inhaled crystalline silica dust (cSiO2) is linked to systemic lupus erythematosus, rheumatoid arthritis, systemic sclerosis, and anti-neutrophil cytoplasmic autoantibody vasculitis. Each disease has a characteristic autoantibody profile used in diagnosis and implicated in pathogenesis. A role for cSiO2 in modulating humoral autoimmunity in vivo is supported by findings in mice, where respirable cSiO2 induces ectopic lymphoid structures as well as inflammation in exposed lungs across genetically diverse backgrounds. In lupus-prone mice cSiO2 exposure also leads to early onset autoantibody production and accelerated disease. Elevated autoantibody levels in bronchoalveolar lavage fluid (BALF) and lung transcriptome analysis suggest that the lung is a hub of cSiO2-evoked autoimmune activity. However, mechanisms by which cSiO2 and lung microenvironments interact to promote autoantibody production remain unclear. We previously demonstrated elevated anti-DNA Ig in BALF but not in lung cell cultures from cSiO2-exposed C57BL/6 mice, suggesting that BALF autoantibodies did not arise locally in this non-autoimmune strain. Autoantibodies were also elevated in BALF of cSiO2-exposed lupus-prone BXSB mice. In this report we test the hypothesis that dysregulated autoreactive B cells recruited to cSiO2-exposed lungs in the context of autoimmune predisposition contribute to local autoantibody production. We found that anti-DNA and anti-myeloperoxidase (MPO) Ig were significantly elevated in cultures of TLR ligand-stimulated lung cells from cSiO2-exposed BXSB mice. To further explore the impact of strain genetic susceptibility versus B cell intrinsic dysfunction on cSiO2-recruited B cell fate, we used an anti-basement membrane autoantibody transgenic (autoAb Tg) mouse line termed M7. In M7 mice, autoAb Tg B cells are aberrantly regulated and escape from tolerance on the C57BL/6 background. Exposure to cSiO2 elicited prominent pulmonary B cell and T cell aggregates and autoAb Tg Ig were readily detected in lung cell culture supernatants. Taken together, diverse disease-relevant autoreactive B cells, including cells specific for DNA, MPO, and basement membrane, are recruited to lung ectopic lymphoid aggregates in response to cSiO2 instillation. B cells that escape tolerance can contribute to local autoantibody production. Our demonstration of significantly enhanced autoantibody induction by TLR ligands further suggests that a coordinated environmental co-exposure can magnify autoimmune vulnerability.

Project description:Background & aimsIncreased serum IgG and autoantibodies suggest involvement of B cells in autoimmune hepatitis (AIH). The aim of this study was to assess levels of B cell activating factor of the tumour necrosis family (BAFF), IL-21, and circulating B cell populations in AIH and correlate these to treatment response.MethodsBAFF and IL-21 levels were determined in 66 patients with AIH before treatment and 10 healthy controls. Flow cytometry was performed on circulating B cells of 10 patients with AIH and 12 healthy controls.ResultsBased on BAFF and IL-21 levels, untreated patients with AIH were divided into 3 groups: 27 (41%) patients with normal BAFF and IL-21 (normal BAFF), 27 (41%) patients with elevated BAFF but normal IL-21 (high BAFF), and 12 (18%) patients with elevated IL-21 (high IL-21). The high BAFF group presented with higher bilirubin compared with the normal BAFF and high IL-21 groups (159 vs. 26 vs. 89 μmol/L; p = 0.001; Mann-Whitney U test). After 12 months of treatment, 54% of the high BAFF group reached remission compared with 34% of the normal BAFF group and 0% of the high IL-21 group (p = 0.006, Chi-square test). During follow-up, 3 patients (25%) with high IL-21 developed primary sclerosing cholangitis (PSC) variant syndrome. Autoimmune-associated B cells were increased in patients with AIH compared with healthy controls (4.4 vs. 1.4%; p = 0.003, Mann-Whitney U test). BAFF levels were correlated positively with naïve B cells (p = 0.01) and negatively with class-switched B cells (p = 0.003) and nonclass-switched B cells (p = 0.005, Spearman correlation).DiscussionUsing BAFF and IL-21, we identified different immunological phenotypes of AIH with a different presentation, treatment response, and outcome. Patients with high IL-21 had the poorest treatment response and a risk of developing PSC variant syndrome. BAFF level was related to shifts in circulating B-cell populations.Lay summaryIn patients with untreated autoimmune hepatitis (AIH), circulating B-cell activating factor of the tumour necrosis family (BAFF), IL-21, and B-cell populations were determined. Three subgroups were identified: with (1) normal BAFF and IL-21, (2) elevated BAFF and normal IL-21, and (3) elevated IL-21. Remission after 1-year treatment occurred in 54, 34, and 0% in Groups 1, 2, and 3, respectively. Group 2 had higher bilirubin, indicating more liver dysfunction. In 25% of patients with high IL-21, AIH-PSC variant syndrome developed, but none in the other groups. Autoimmune-associated B cells were elevated and BAFF levels correlated with certain B cells.

Dataset Information

Blockade of B-cell-activating factor suppresses lupus-like syndrome in autoimmune BXSB mice.

Publications

Blockade of B-cell-activating factor suppresses lupus-like syndrome in autoimmune BXSB mice.

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