The TRAP1 monoclonal antibody specifically binds to CD154. CD154 is a 39 kDa type II membrane glycoprotein that is a member of the tumor necrosis factor superfamily, Tumor necrosis factor ligand superfamily member 5 (TNFSF5). CD154 is expressed on a variety of cell types including activated CD4+ T cells and some CD8+ T cells, NK cells, mast cells and basophils. CD154 is also known as CD40 ligand (CD40L); it serves as a ligand for CD40 that is expressed on B cells, macrophages, and dendritic cells. The expression of CD154 by activated T-helper cells costimulates B-cell activation and proliferation through binding to CD40 expressed on B cells. In response to T-dependent antigens, the CD154 and CD40 interaction is required for B-lymphocyte differentiation, including immunoglobulin production and isotype switching and memory B cell generation. The TRAP1 antibody can partially block T cell-B cell interaction and inhibit the subsequent proliferation, differentiation, and memory formation of B cells. It has been reported that patients with X-linked hyper-IgM syndrome have defective expression of functional CD154 due to mutations in the CD40LG gene that encodes CD154.
Clone TRAP1 also cross-reacts with phorbol myristic acetate (PMA) plus Ca++ ionophore (A23187)-treated blood lymphocytes of baboon and both rhesus and cynomolgus macaque monkeys. TRAP1 reactivity on PMA plus Ca++ ionophore-activated non-human primate lymphocytes is similar to that observed with normal human donor lymphocytes following overnight (but not six-hour) incubation at 37°C.