Innate and adaptive signals enhance differentiation and expansion of dual-antibody autoreactive B cells in lupus.

Sang, Allison; Danhorn, Thomas; Peterson, Jacob N; Rankin, Andrew L; O'Connor, Brian P; Leach, Sonia M; Torres, Raul M; Pelanda, Roberta · Nat Commun · 2018

basic_science · Level V

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Abstract

Autoreactive B cells have a major function in autoimmunity. A small subset of B cells expressing two distinct B-cell-antigen-receptors (B<sub>2R</sub> cells) is elevated in many patients with systematic lupus erythematosus (SLE) and in the MRL(/lpr) mouse model of lupus, and is often autoreactive. Here we show, using RNAseq and in vitro and in vivo analyses, signals that are required for promoting B<sub>2R</sub> cell numbers and effector function in autoimmune mice. Compared with conventional B cells, B<sub>2R</sub> cells are more responsive to Toll-like receptor 7/9 and type I/II interferon treatment, display higher levels of MHCII and co-receptors, and depend on IL-21 for their homeostasis; moreover they expand better upon T cell-dependent antigen stimulation, and mount a more robust memory response, which are characteristics essential for enhanced (auto)immune responses. Our findings thus provide insights on the stimuli for the expansion of an autoreactive B cell subset that may contribute to the etiology of SLE.

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