Background/Purpose: Interferon-alpha (IFNα) is elevated in Systemic Lupus Erythematosus (SLE) and is thought to play a central role in its pathogenesis. Amongst IFNα’s many effects on the immune system are direct effects on B cells, leading to enhanced B cell signaling and survival. It also plays a major role in the induction of B cell activating factor (BAFF). While past studies have explored the effects BAFF on B cell tolerance, little work has focused on how IFNα directly affects this process. We hypothesize that elevated levels of IFNα directly contribute to the breach of B cell tolerance in SLE. To address this question, we used an adenoviral vector that expresses mouse IFNα (mDEF201) to induce sustained elevations of serum IFNα in the 3H9 mouse model of B cell tolerance.

Methods: 6-8 week old 3H9 mice, which contain a knock-in Ig heavy chain derived from a DNA-specific hybridoma, were injected IV with 10⁷ PFU of Ad-mIFNα (mDEF201) or Ad-dI70-3 (empty vector). At 2 weeks post-treatment immune cell populations in the spleen and bone marrow were examined by flow cytometry, and anti-DNA antibody production was measured by ELISA. Serum levels of IFNα were quantified by ELISA and IFN-induced gene expression was assessed by qRT-PCR.

Results: Mice administered mDEF201 had elevated serum levels of IFNα and increased mRNA expression of several IFN-inducible genes. Elevated IFNα was associated with a marked increase in the levels of anti-ss/dsDNA autoantibodies, signifying a breach of B cell tolerance. Consistent with this idea, mDEF201 infected mice displayed several abnormalities suggestive of altered B cell homeostasis, including increased numbers of mature follicular/marginal zone B cells, increased frequencies of activated B cells, age-associated B cells (ABC), germinal center B cells, and CD138⁺ plasma cells. These changes occurred in the setting of minimal changes to the T cell compartment. In the bone marrow, infected mice demonstrated reduced receptor editing, consistent with impaired tolerance induction. To assess the effect of IFNα on B cell anergy, the fate of Igλ1⁺ expressing B cells, a well-characterized dsDNA-reactive anergic B cell population, was examined. Igλ1⁺ B cells demonstrated several features of impaired anergy such as enhanced selection in to the mature B cell follicular compartment, increased levels of activation markers, and increased germinal center recruitment; however, anti-dsDNA Igλ1⁺ levels were not increased, suggesting only a partial breach of anergy. To determine whether altered B cell tolerance in infected mice was due to a direct effect of IFNα on B cells, 3H9 mice with B cell-specific knockout of IFNAR were produced. In these mice several of the IFNα-induced changes were reversed, such as enhanced B cell selection into the follicular, marginal zone, and ABC populations, enhanced B cell activation, and elevated levels of anti-dsDNA antibodies, highlighting the important role of IFNα-B cell interactions in these results.

Conclusion: These data indicate that IFNα may be a major contributing factor to the breach B cell tolerance in SLE through direct effects on autoreactive B cells that impact multiple mechanisms of tolerance, leading to enhanced B cell activation, generation of ABCs and autoantibody production.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/interferon-alpha-disrupts-multiple-b-cell-tolerance-mechanisms-in-3h9-mice/