The FGK4.5-CP133 monoclonal antibody is a chimeric version of the original FGK4.5 antibody. The variable domain sequences are identical to the original FGK4.5 but the constant region sequences have been switched from rat IgG2a to mouse IgG2a. The FGK4.5-CP133 antibody contains no Fc mutations just as the original rat IgG2a antibody does not. The FGK4.5-CP133 monoclonal antibody reacts with mouse CD40 also known as Bp50. CD40 is a 48 kDa type I transmembrane glycoprotein that belongs to the tumor necrosis factor receptor (TNFR) superfamily. CD40 is expressed broadly on antigen-presenting cells (APCs) such as dendritic cells, B cells, macrophages, and monocytes as well as non-immune endothelial cells, basal epithelial cells, and a range of tumors. Upon binding to its ligand CD154, CD40 acts as a costimulatory molecule for the activation of B cells, dendritic cells, monocytes, and other APCs. CD40 plays roles in B cell activation, differentiation, proliferation and Ig isotype switching as well as dendritic cell maturation. Agonistic CD40 monoclonal antibodies have been shown to activate APCs and promote anti-tumor T cell responses. The FGK4.5 antibody is an agonistic antibody that has been shown to activate CD40 expressing APCs. FGK4.5 can also be used to inhibit CD40/CD154 interaction in vitro and in vivo.

See the references for the original rat IgG2a FGK4.5 antibody (https://bioxcell.com/catalogsearch/result/?q=BP0016-2).