The 7B11 (also known as CMSSC-7B11) monoclonal antibody specifically binds to human GARP (Glycoprotein A repetitions predominant). The LRRC32 (Leucine rich repeat containing 32) gene encodes the 662 amino acid-residue, 80 kDa transmembrane GARP glycoprotein that has an extracellular region composed primarily of 20 leucine-rich repeats. GARP is specifically expressed on Treg cells activated through the T cell receptor (TCR). Ectopic expression of GARP in human naïve T cells inhibited their proliferation and cytokine secretion upon TCR activation. Remarkably, GARP over-expression in naïve T cells induced expression of FoxP3 and endowed them with a partial suppressive function. The extracellular, but not the cytoplasmic region, of GARP was necessary for these functions. GARP serves as a receptor for latent TGF-beta which may play a role in the suppressive action of Treg cells. GARP is also expressed on platelets and other tissues, however the function on these cells is not known.
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.