The L293 monoclonal antibody specifically binds to CD28 which is also known as Tp44 or T44. The CD28 antigen is a 44 kDa homodimeric type I transmembrane glycoprotein which is present on most mature T cells, thymocytes, and plasma cells. CD28 is a cell-adhesion molecule (CAM) that functions as a receptor for CD80 (B7-1) and CD86 (B7-2) antigens, which are present on activated B lymphocytes, monocytes, and dendritic cells. Interaction of the CD28 antigen with CD80 or CD86 antigens, or both, co-stimulates CD2 and CD3 antigen/T-cell antigen receptor (TCR)-dependent T-cell-mediated proliferation and cytotoxicity. The L293 antibody has been demonstrated to bind to the same molecule as clone CD28.2, another CD28-specific antibody.
The antibody was conjugated to BD Horizon BUV615 which is part of the BD Horizon Brilliant™ Ultraviolet family of dyes. This dye is a tandem fluorochrome with an Ex Max near 350 nm and an Em Max near 615 nm. BD Horizon Brilliant BUV615 can be excited by the ultraviolet laser (355 nm) and detected with a 610/20 filter and a 595 nm LP. Due to the excitation of the acceptor dye by the blue/yellow-green laser line, there may be significant spillover into channels detecting PE-CF594 like emissions (eg, 610/20-nm filter).