Background/Purpose: Polymorphisms of the transcription factors Ikaros (IKZF1) and Aiolos (IKZF3), which are essential for the maturation, differentiation and survival of B cells, have been linked to systemic autoimmunity. The Cereblon modulator CC-220, known to induce the degradation of Ikaros and Aiolos, is being explored as a therapeutic option in Systemic Lupus Erythematosus (SLE). The involvement of IKZF1 and 3 in other autoimmune diseases is poorly known, and their effects on B cell activation and differentiation in the context of autoimmunity have been only partially described. Aim of this study was to evaluate the expression of IKZF1 and IKZF3 in the salivary glands (SGs) of patients with Sjogren’s syndrome (SS) and the effects of CC-220 on the TLR7-mediated activation and plasmablast differentiation of B cells isolated from patients with Sjogren and SLE.

Methods:

SG biopsies of patients with SS (n=29) and sicca controls (n=11) were analysed by immunohistochemistry for IKZF1 and IKZF3 expression using a semi-quantitative (SQ) score (0-3, based on number of positive cells) to quantify expression. Sequential sections were stained for B and T cells, and patients were classified into Ectopic Lymphoid Structures (ELS) positive and negative. CD19⁺ B cells were isolated from the peripheral blood of patients with SLE (n=16) and Sjogren’s (n=4), triggered with TLR7 ligand Resiquimod +/- IFNa, with or without CC-220 (1, 10, 100 nM). After 5 days, cells were analysed by FACS, IgG and IgM measured by ELISA and ANA by immunofluorescence. In parallel experiments, SLE B cells (n=7) were differentiated into plasmablasts in vitro by stimulation with IL-2, IL-10, IL-15, CD40L & Resiquimod for 5 days and analysed as above.

Results:

Ikaros expression was significantly higher in the SGs of SS patients vs sicca controls (p<0.05), while aiolos was expressed at similar levels. SS patients with ectopic lymphoid structure (ELS) had significantly higher scores than ELS negative for both IKZF1 (p=0.041) and IKZF3 (p=0.016). CC-220 significantly inhibited the TLR7 and IFNa-mediated production of IgM and IgG from B cells from SLE and Sjogren’s patients, in a dose dependent manner, inhibited the production of anti-nuclear antibodies, and significantly reduced the number of CD27⁺ memory B cells. CC-220 significantly inhibited in vitro differentiation of plasmablasts (CD19⁺CD20⁻CD27^hiCD38^hi) from SLE B cells, while leaving IgD⁺ naïve B cells unaffected.

Conclusion:

This study shows that Ikaros and Aiolos expression in the salivary glands of patients with Sjogren’s syndrome is associated with the presence of ectopic lymphoid structures. CC-220, a cereblon modulator which induces IKZF1/3 degradation, reduced B cell activation and autoantibody production triggered by TLR-7 and IFN-a, and inhibited the differentiation of SLE B cells into plasmablasts. Our work further confirms the relevance of Ikaros and Aiolos in SLE, and suggests that they might be useful therapeutic targets in B cell driven systemic autoimmune diseases, such as Sjogren’s.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/expression-and-functions-of-the-transcription-factors-ikaros-and-aiolos-in-sjogrens-syndrome-and-systemic-lupus-erythematosus/