Mechanistic insights into B-cell activation and autoreactivity regulation in active SLE and remission.

OBJECTIVE

To define cellular and molecular mechanisms distinguishing active systemic lupus erythematosus (SLE) from remission by profiling autoreactive antinuclear antigen- positive (ANA+) and non-autoreactive B cells subsets in three cohorts: active disease (SLE-A), long-term, drug free remission (SLE-R), and healthy controls (HC).

METHODS

Peripheral blood B cells were phenotyped by flow cytometry, including ANA reactivity. Single-cell RNA sequencing (scRNA-seq) was performed on sorted ANA+ and ANA- subsets.

RESULTS

Seven transcriptomic B cell clusters were resolved: quiescent (Naïve 1, Marginal Zone B cells [MZB], IgG Memory 1) and activated (Age-Associated B cells [ABCs], Naïve 2, IgM Memory, IgG Memory 2). SLE-A showed expansion of activated clusters, MZB contraction, and a higher IgG:IgM B cell ratio. SLE-R exhibited an "immunological reset," distinct from healthy homeostasis, with reduced ABCs and IgG Memory 2, persistence of Naïve 2, and partial restoration of MZB and Naïve 1. Interferon-α (IFNa) signaling was elevated across clusters in SLE-A (SLE-A > SLE-R > HC), whereas TNF signaling was enriched in activated clusters across cohorts, with minimal differences between SLE-R and SLE-A. IFNa and TNF scores were inversely correlated. B cells predominantly expressed TNFR2, suggesting immunomodulatory TNF effects in remission. ANA+ cells in HC and SLE-R showed enriched FcγRIIb inhibitory and IL-4/STAT6 signaling, suggesting reinstated regulatory control.

DISCUSSION: Compared to SLE-A, SLE-R was characterized by partial reversion to HC homeostasis with residual activation. These findings delineate immunologic features of remission and suggest therapeutic opportunities, including modulation of TNFR2, FcγRIIb, and IL-4 to help sustain remission.

WHAT IS ALREADY KNOWN ON THIS TOPIC: Some patients with SLE achieve complete clinical remission without treatment, referred as 'immune reset'; the mechanisms that underlie this state have not been well characterized. Healthy individuals and patients with Systemic Lupus Erythematosus (SLE) normally harbor similar frequencies of autoreactive B cells; the checkpoints that regulate activation of these cells are not fully defined.

WHAT THIS STUDY ADDS: B cells, stratified by their reactivity to nuclear antigens (ANA), from active SLE (SLE-A), drug-free remission (SLE-R), and healthy controls (HC) were analyzed using single cell sequencing and flow cytometry. We identified B cells states associated with disease activity; SLE-R displayed a distinct profile that differed from SLE-A and HC. TNF signaling was present in activated B cell subsets in SLE-A and SLE-R. This persistence in SLE-R may reflect an immunomodulatory function of TNF on TNFR2, which is expressed on B cells. ANA+ cells in SLE-R and HC were enriched for inhibitory FcγRIIb and IL-4/STAT6 programs.

HOW THIS STUDY MIGHT AFFECT RESEARCH PRACTICE OR POLICY: The signatures identified help define the "immunological reset" state in patients with SLE-R. We also identified pathways, such as type I IFN, TNFR2, FcγRIIb, IL-4/STAT6 as potential targets for maintaining remission.