1. The essential roles of memory B cells in the pathogenesis of systemic lupus erythematosus.
- Author
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Dörner, Thomas and Lipsky, Peter E.
- Subjects
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B cell receptors , *IMMUNOLOGIC memory , *PLASMA cells , *T helper cells , *TYPE I interferons , *TALL-1 (Protein) - Abstract
Emerging evidence indicates that memory B cells are dysfunctional in systemic lupus erythematosus (SLE). They are hyporesponsive to signalling through the B cell receptor (BCR) but retain responsiveness to Toll-like receptor (TLR) and type I interferon signalling, as well as to T cell-mediated activation via CD40–CD154. Chronic exposure to immune complexes of ribonucleoprotein (RNP)-specific autoantibodies and TLR-engaging or BCR-engaging cargo is likely to contribute to this partially anergic phenotype. TLR7 or TLR8 signalling and the resulting production of type I interferon, as well as the sustained activation by bystander T cells, fuel a positive feedforward loop in memory B cells that can evade negative selection and permit preferential expansion of anti-RNP autoantibodies. Clinical trials of autologous stem cell transplantation or of B cell-targeted monoclonal antibodies and chimeric antigen receptor (CAR) T cells have correlated replenishment of the memory B cell population with relapse of SLE. Moreover, the BCR hyporesponsiveness of memory B cells might explain the failure of non-depleting B cell-targeting approaches in SLE, including BTK inhibitors and anti-CD22 monoclonal antibodies. Thus, targeting of dysfunctional memory B cells might prove effective in SLE, while also avoiding the adverse events of broad-spectrum targeting of B cell and plasma cell subsets that are not directly involved in disease pathogenesis. BCR-independent memory B cell reactivation via TLR7 or TLR8 activation, type I interferon production, immune complex formation and T helper cell signalling is central in SLE pathogenesis. Dörner and Lipsky discuss the potential of targeting these pathways to eliminate autoreactive memory B cells and plasma cells in SLE. Key points: In systemic lupus erythematosus (SLE), memory B cells are hyporesponsive to B cell receptor (BCR) stimulation but can be activated upon engagement of Toll-like receptors (TLRs) and interaction with T cells (mainly via the CD40–CD40L axis). Both innate and adaptive immune signalling by B cells ('bridging') contribute to SLE pathology, possibly via a pathogenic positive feedforward loop. This feedforward loop is accentuated by anti-ribonucleoprotein (anti-RNP) autoantibodies sequestering RNP antigens, which, when internalized via the BCR, stimulate TLR7 and TLR8 signalling and type I interferon production. Incomplete X chromosomal inactivation of TLR7, TLR8 and CD40L might further contribute to such a positive feedforward loop, thereby potentially explaining the female sex bias in SLE. Clinical outcomes of B cell depletion in SLE, via anti-CD20 or anti-CD19 or autologous stem cell transplantation, have clearly associated relapse with memory B cell repletion, independently of the recurrence of naive B cells or autoantibodies. The safety and efficacy of CD19-targeted and BCMA-targeted chimeric antigen receptor (CAR) T cells, or bispecific T cell engagers in SLE, and their impact on tissue-resident memory B cells remain to be elucidated. BCR signalling inhibition approaches did not result in sufficient efficacy potentially owing to an incomplete impact on memory B cells. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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