CD40 blockade hampers IgG class-switch while enhancing Granzyme B production by transitional B cells

CD40-CD40L interaction is crucial for the interplay between B and T cells and determines B-cell fate. Here, we investigated the effects of CD40-CD40L inhibition on B-cell subsets and cytokine production using the non-depleting monoclonal anti-CD40 antibody CFZ534. CFZ534 had no impact on B-cell viability but inhibited TLR9-agonistic (CpG-ODN) CD40L- as well as CD40L-mediated proliferation. The plasmablast subset was reduced after stimulation with CpG-ODN + CD40L, but this effect was completely restored by CFZ534-mediated CD40 blockade. IgG as well as IgM-secreting cells were significantly reduced in the presence of CFZ534 upon CD40L stimulation. CpG-ODN, but not CD40L, induced Granzyme B production in B cells after CD40-blockade and CpG-ODN/CD40L stimulation. Moreover, we found that IL-10 and Granzyme B were produced by separate B-cell subsets. Hence, CD40-blockade mediated by CFZ534 increased Granzyme B production and decreased IL-10 production in CD24hiCD38hi B cells with a transitional phenotype and led to a significant decrease in the expression of the pro-inflammatory cytokines IL-6, IL-12p35, and IL-23p19 and TNFα in a B and CD4 + TH-cell co-culture system. Based on these preclinical results, CD40 blockade by the Fc-silent, non-depleting monoclonal antibody CFZ534 exerts an anti-inflammatory effect on B cells, including hampering the IgG class switch without affecting their viability.