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.
The antibody was conjugated to BD Horizon™ BUV661 which is part of the BD Horizon Brilliant™ Ultraviolet family of dyes. This dye is a tandem fluorochrome of BD Horizon BUV395 with an Ex Max of 348-nm and an acceptor dye with an Em Max at 661-nm. BD Horizon Brilliant BUV661 can be excited by the ultraviolet laser (355 nm) and detected with a 670/25 filter and a 630 nm LP. Due to cross laser excitation of this dye, there may be significant spillover into channels detecting APC-like emissions (eg, 670/25-nm filter).
Due to spectral differences between labeled cells and beads, using BD™ CompBeads can result in incorrect spillover values when used with BD Horizon BUV661 reagents. Therefore, the use of BD CompBeads or BD CompBeads Plus to determine spillover values for these reagents is not recommended. Different BUV661 reagents (eg, CD4 vs. CD45) can have slightly different fluorescence spillover therefore, it may also be necessary to use clone-specific compensation controls when using these reagents.