Abstract
Germinal centers (GCs) are the primary sites of clonal B cell expansion and affinity maturation, directing the production of high-affinity antibodies. This response is a central driver of pathogenesis in autoimmune diseases, such as systemic lupus erythematosus (SLE), but the natural history of autoreactive GCs remains unclear. Here, we present a novel mouse model where the presence of a single autoreactive B cell clone drives the TLR7-dependent activation, expansion, and differentiation of other autoreactive B cells in spontaneous GCs. Once tolerance was broken for one self-antigen, autoreactive GCs generated B cells targeting other self-antigens. GCs became independent of the initial clone and evolved toward dominance of individual clonal lineages, indicating affinity maturation. This process produced serum autoantibodies to a breadth of self-antigens, leading to antibody deposition in the kidneys. Our data provide insight into the maturation of the self-reactive B cell response, contextualizing the epitope spreading observed in autoimmune disease.
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•Single autoreactive B cell clone drives expansion of WT B cells in germinal centers•Autoreactive germinal centers composed of WT B cells become self-sufficient•Autoreactive and foreign antigen germinal centers evolve clonally at similar rates•Clonal expansion of WT B cells in germinal centers underlies epitope spreading
Following the natural history of autoreactive germinal centers in vivo opens a window into how self-tolerance is broken in lupus and other complex autoimmune diseases.