Abstract
Systemic lupus erythematosus is a complex autoimmune disease with significant morbidity that demands further examination of tolerance-inducing treatments. Short-term treatment of lupus-prone NZB/WF1 mice with combination CTLA4Ig and anti-CD40 ligand, but not single treatment alone, suppresses disease for >6 mo via modulation of B and T cell function while maintaining immune responses to exogenous Ags. Three months after a 2-wk course of combination costimulatory blockade, we found a modest decrease in the number of activated T and B cells in both combination and single-treatment cohorts compared with untreated controls. However, only combination treatment mice showed a 50% decrease in spare respiratory capacity of splenic B and T cells. RNA sequencing and gene set enrichment analysis of germinal center (GC) B cells confirmed a reduction in the oxidative phosphorylation signature in the combination treatment cohort. This cohort also manifested increased expression of BCR-associated signaling molecules and increased phosphorylation of PLCγ in GC B cells after stimulation with anti-IgG and anti-CD40. GC B cells from combination treatment mice also displayed a signature involving remodeling of GPI-linked surface proteins. Accordingly, we found a decrease in cell surface expression of the inhibitory molecule CD24 on class-switched memory B cells from aged NZB/W mice that corrected in the combination treatment cohort. Because both a profound decrease in BCR signaling and remodeled immune cell metabolism enhance loss of tolerance in lupus-prone mice, our findings help to explain the restoration of tolerance observed after short-term combination costimulatory blockade.