The extrafollicular response is sufficient to drive initiation of autoimmunity and early disease hallmarks of lupus

Front Immunol. 2022 Dec 14:13:1021370. doi: 10.3389/fimmu.2022.1021370. eCollection 2022.

Abstract

Introduction: Many autoimmune diseases are characterized by germinal center (GC)-derived, affinity-matured, class-switched autoantibodies, and strategies to block GC formation and progression are currently being explored clinically. However, extrafollicular responses can also play a role. The aim of this study was to investigate the contribution of the extrafollicular pathway to autoimmune disease development.

Methods: We blocked the GC pathway by knocking out the transcription factor Bcl-6 in GC B cells, leaving the extrafollicular pathway intact. We tested the impact of this intervention in two murine models of systemic lupus erythematosus (SLE): a pharmacological model based on chronic epicutaneous application of the Toll-like receptor (TLR)-7 agonist Resiquimod (R848), and 564Igi autoreactive B cell receptor knock-in mice. The B cell intrinsic effects were further investigated in vitro and in autoreactive mixed bone marrow chimeras.

Results: GC block failed to curb autoimmune progression in the R848 model based on anti-dsDNA and plasma cell output, superoligomeric DNA complexes, and immune complex deposition in glomeruli. The 564Igi model confirmed this based on anti-dsDNA and plasma cell output. In vitro, loss of Bcl-6 prevented GC B cell expansion and accelerated plasma cell differentiation. In a competitive scenario in vivo, B cells harboring the genetic GC block contributed disproportionately to the plasma cell output.

Discussion: We identified the extrafollicular pathway as a key contributor to autoimmune progression. We propose that therapeutic targeting of low quality and poorly controlled extrafollicular responses could be a desirable strategy to curb autoreactivity, as it would leave intact the more stringently controlled and high-quality GC responses providing durable protection against infection.

Keywords: B cells; TLR7; autoantibodies; autoimmunity; extrafollicular responses; germinal centers; systemic lupus erythematosus.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Autoimmunity*
  • B-Lymphocytes
  • Germinal Center
  • Lupus Erythematosus, Systemic*
  • Mice
  • Plasma Cells

Associated data

  • Dryad/10.5061/dryad.zs7h44jc2