The L272 monoclonal antibody specifically recognizes CD26 which is also known as Dipeptidyl peptidase IV (DPP IV), a serine protease. CD26 is a ~120 kDa type II transmembrane glycoprotein that is encoded by DPP4 and belongs to the DPP4 activity and/or structure homologue (DASH) protein family. It is associated with the binding of the TAT transactivating protein of the HIV. CD26 and CD45 act in a costimulatory fashion on T lymphocytes. Present on peripheral blood T lymphocytes, the CD26 antigen is upregulated on phytohemagglutinin (PHA) and concanavalin A (Con A)-stimulated peripheral blood mononuclear cells (PBMCs). The CD26 antigen is found on approximately 50% of CD4 and approximately 30% of CD8 cells. It is also found on some mature thymocytes, B cells, natural killer (NK) cells, monocytes, macrophages, epithelial cells, EBV transformed B-cell lines, and hairy cell leukemia. Absolute numbers of CD4+CD26+ and CD8+CD26+ cells are reported to be lower in HIV-positive individuals. The CD26-CD4+ cell appears to be a reservoir for HIV. CD26 bright CD4 lymphocytes are CD25+ and CD45RO+ memory T lymphocytes. The CD26 antigen can serve as a receptor for the coronavirus, MERS-CoV.
The antibody was conjugated to BD Horizon™ BV650 which is part of the BD Horizon Brilliant™ Violet family of dyes. This dye is a tandem fluorochrome of BD Horizon BV421 with an Ex Max of 405-nm and an acceptor dye with an Em Max at 650-nm. BD Horizon BV650 can be excited by the violet laser and detected in a filter used to detect APC-like dyes (eg, 660/20-nm filter). Due to the excitation and emission characteristics of the acceptor dye, there will be spillover into the APC and Alexa Fluor® 700 detectors. However, the spillover can be corrected through compensation as with any other dye combination.