Quantitative interactomic of CD40 in primary B cells

Over the past few decades, antibody-based therapies have emerged as an additional tool to treat patients developing cancer and auto-immune diseases. The natural properties of the developed antibodies may lead to agonist or blocking functions for the targeted molecule. Thus, antibodies developed for clinical trials are extensively analyzed in vitro and in vivo for safety and efficacy, yet they are not routinely evaluated for their potential signaling effectiveness. Thus, developing preclinical models to predict potential adverse effects due to abnormal signaling remains a primary concern. Here, we generated a knock-in mouse that expresses a chimeric CD40 molecule composed of a human extracellular domain, a human transmembrane segment, fused to a mouse intra-cytoplasmic tail in which a OneStregTag (OST) has been added (referred to hereafter as hCD40OST). CD40 (also known as TNFRSF5) is a critical transmembrane molecule expressed on B cells and on myeloid cells including dendritic cells (DCs) [1]. In B cells, CD40 engagement by its ligand CD40L (CD154) is essential to promote immunoglobulin class switching, memory differentiation, and germinal center formation [2]. Stimulation of CD40 primarily results in the recruitment of the tumor necrosis factor receptor (TNF-R)–associated factor (TRAF) molecules, which subsequently induces the activation of nuclear factor-kappa B (NF-κB), mitogen-activated protein kinases (MAPK)-p38, and Jun N-terminal kinase (JNK) signaling pathways [[3], [4], [5], [6]]. Accordingly, CD40 constitutes an attractive target to modulate B cell responses, and several CD40 monoclonal antibodies (mAbs) have been developed and tested, while some are still in early-phase clinical trials [7].