Costimulatory blockade modifies germinal center B cell function in NZB/W F1 mice

Abstract

Abstract Systemic lupus erythematosus (SLE) is a complex autoimmune disease with significant morbidity and mortality - demanding further examination of disease reducing treatments. Previously, we showed that a 2-week course of combined CTLA4Ig and anti-CD40L costimulatory blockade prevented loss of tolerance to dsDNA in NZB/W mice while maintaining immune function against exogenous antigen, explained by an altered selection of autoreactive B cells in germinal centers (GC). Here, we examined both B and T cells to clarify if restoration of tolerance is due to a change in GC B cell profile or a decrease in T cell help. 3 months after treatment, large germinal centers persisted in the treated group, but due to smaller spleen size total GC B cells and TFH Cells were decreased compared with controls. The metabolic profile of splenic B and T cells showed a decreased spare respiratory capacity in both subsets and a decrease in B cell glycolysis among the treated group. RNA-seq analysis of GC dark zone and light zone B cells from treated mice showed decreased expression of markers of oxidative phosphorylation and cell proliferation and increased expression of signaling molecules downstream of BCR, including PLCγ, compared with untreated controls. GC B cell stimulation assays showed a delay in phosphorylation of PLCγ in response to anti-IgG in treated mice. These data show a long-lasting effect of short-term costimulatory blockade on both B and T cells with metabolic remodeling of GC B cells and an alteration of BCR signaling. Since both a profound decrease in BCR signaling and an increase in B cell glycolysis have been reported to enhance loss of tolerance in lupus prone mice, our findings help to explain the restoration of tolerance observed after treatment.