Cutting Edge: A Threshold of B Cell Costimulatory Signals Is Required for Spontaneous Germinal Center Formation in Autoimmunity

Cognate interactions between autoreactive B and T cells promote systemic lupus erythematosus pathogenesis by inter alia facilitating spontaneous germinal center (GC) formation. Whereas both myeloid and B cell APCs express B7 ligands (CD80 and CD86), the prevailing model holds that dendritic cell costimulation is sufficient for CD28-dependent T cell activation. In this study, we report that B cell-intrinsic CD80/CD86 deletion unexpectedly abrogates GCs in murine lupus. Interestingly, absent GCs differentially impacted serum autoantibodies. In keeping with distinct extra follicular and GC activation pathways driving lupus autoantibodies, lack of GCs correlated with loss of RNA-associated autoantibodies but preserved antidsDNA and connective tissue autoantibody titers. Strikingly, even heterozygous B cell CD80/CD86 deletion was sufficient to prevent autoimmune GCs and RNA-associated autoantibodies. Together, these findings identify a key mechanism whereby B cells promote lupus pathogenesis by providing a threshold of costimulatory signals required for autoreactive T cell activation.

Automated summary

The deletion of B cell-intrinsic CD80/CD86 unexpectedly leads to the disappearance of germinal centers in lupus mice, impacting the production of serum autoantibodies. The absence of germinal centers is associated with the loss of RNA-associated autoantibodies, while preserving anti-dsDNA and connective tissue autoantibody titers.