CD40, a 50kDa transmembrane member of the tumor-necrosis factor (TNF) receptor (TNFR) superfamily of molecules, plays a key role in adaptive immune responses. This includes contact-mediated signals to B cells from activated T lymphocytes, as well as costimulatory interactions between T cells and other antigen-presenting cells (APC), such as dendritic cells (DC) and macrophages. CD40-mediated interactions between B and T cells make important contributions to the development of an optimal humoral memory response (Bishop 2009).
CD40 lacks intrinsic enzymatic activity and therefore depends on cytoplasmic (CY) adaptor molecules referred to as TNFR-associated factors (TRAFs) for delivery of signals to the cytoplasm. CD40 engagement on B cells stimulates the binding of TRAFs to the CD40 CY domain. This in turn stimulates kinase activity and gene expression pathways that lead to a variety of responses, including B cell...
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