Excessive CD11c + Tbet + B cells promote aberrant T FH differentiation and affinity-based germinal center selection in lupus

Excessive self-reactive and inadequate affinity-matured antigen-specific antibody responses have been reported to coexist in lupus, with elusive cellular and molecular mechanisms. Here, we report that the antigen-specific germinal center (GC) response-a process critical for antibody affinity maturation-is compromised in murine lupus models. Importantly, this defect can be triggered by excessive autoimmunity-relevant CD11c Tbet age-associated B cells (ABCs). In B cell-intrinsic Ship-deficient (ShipΔB) lupus mice, excessive CD11c Tbet ABCs induce deregulated follicular T-helper (T ) cell differentiation through their potent antigen-presenting function and consequently compromise affinity-based GC selection. Excessive CD11c Tbet ABCs and deregulated T cell are also present in other lupus models and patients. Further, over-activated Toll-like receptor signaling in Ship-deficient B cells is critical for CD11c Tbet ABC differentiation, and blocking CD11c Tbet ABC differentiation in ShipΔB mice by ablating MyD88 normalizes T cell differentiation and rescues antigen-specific GC responses, as well as prevents autoantibody production. Our study suggests that excessive CD11c Tbet ABCs not only contribute significantly to autoantibody production but also compromise antigen-specific GC B-cell responses and antibody-affinity maturation, providing a cellular link between the coexisting autoantibodies and inadequate affinity-matured antigen-specific antibodies in lupus models and a potential target for treating lupus.