Excessive CD11c+Tbet+ B cells promote aberrant TFH 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 (Ship Delta B) lupus mice, excessive CD11c(+)Tbet(+) ABCs induce deregulated follicular T-helper (T-FH) cell differentiation through their potent antigen-presenting function and consequently compromise affinity-based GC selection. Excessive CD11c(+)Tbet(+) ABCs and deregulated T-FH 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 Ship Delta B mice by ablating MyD88 normalizes T-FH 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.