Background/Purpose: Systemic Lupus Erythematosus (SLE) is characterized by the production of anti-nuclear antibodies that deposit within tissues leading to organ damage. A central mediator of SLE pathogenesis is interferon-alpha (IFNα), which is elevated in the serum of SLE patients. IFNα has been shown to enhance B cell signaling and promote the survival of B cells. It also plays a major role in the induction of B cell activating factor (BAFF). While past studies have explored the indirect effects of IFNα through BAFF on B cell tolerance, little work has focused on how IFNα itself 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 have obtained an adenoviral vector encoding mouse IFNα (mDEF201), which we are using to induce sustained elevations of serum IFNα in several well characterized mouse models of B cell tolerance.

Methods: IgHEL/sHEL double transgenic mice, with transgenes encoding anti-hen egg white lysozyme (HEL) Ig and soluble HEL were injected IV with 10⁷ PFU of Ad-mIFNα (mDEF201) or Ad-dI70-3 (empty control vector). At 2 weeks post-treatment immune cell populations in the spleen and bone marrow were examined by flow cytometry, and anti-HEL antibody production was measured by ELISA. Serum levels of IFNα were quantified by ELISA and tissue-specific IFN-induced gene expression was assessed by qRT-PCR.

Results: 6-8 week old C57BL/6 mice administered with mDEF201, but not Ad-dI70-3, showed robust elevations of serum IFNα from 48h to 2 weeks post infection. At 2 weeks post injection expression of several IFN-inducible genes (2-5’ Oas, Pkr, Mx1, Ifit1, Irf7, Isg15), but not Baff, was elevated in the liver, bone marrow and spleen of infected mice. B cell homeostasis and activation were altered in IgHEL/sHEL mice following administration of mDEF201. At 2 weeks post infection mice displayed increased proportions of total splenic B cells (B220⁺CD19⁺). Infected mice also displayed an increase in the proportion of mature B cells (B220⁺CD93^–) and decreased proportions of immature transitional 1 and 2 B cells (CD24⁺CD21^-/int). Upregulation of the B cell activation marker B7.2 (CD86⁺) and down regulation of surface IgM^a was observed on mature B cells in infected mice suggestive of enhanced B cell signalling. At 2 weeks post infection mice also displayed increased proportions of germinal center B cells (B220⁺GL7⁺CD95⁺). Upregulation of CD86 and enhanced maturation of the B cell compartment was not seen following infection of mice with Ad-dI70-3. Anti-HEL IgM^a antibody production was increased 2 weeks post infection signifying a breach of B cell tolerance in IgHEL/sHEL mice. No differences in T cell populations or activation state were seen suggesting that the observed effects on B cells occurred largely from altered B and not T cell function.

Conclusion: IFNα may be playing an important role in breaching B cell tolerance in SLE not only through the induction of BAFF but also through its direct actions on B cells. Further research into the effects of IFNα on these processes may prove IFNα to be a more effective therapeutic target than BAFF for SLE patients.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/interferon-alpha-disrupts-tolerance-in-a-mouse-model-of-b-cell-anergy/