The OX-41 monoclonal antibody specifically reacts with the rat signal-regulatory protein (SIRP). The rat SIRP (CD172) is a 110-120-kDa type 1 transmembrane protein with three extracellular immunoglobulin superfamily domains and two intracellular Immunoreceptor Tyrosinebased Inhibitory Motifs (ITIM). The SIRP ITIMs are phosphorylated in response to activation by growth hormone, epidermal growth factor, and integrin-mediated cell adhesion. The phosphorylated SIRP associates with tyrosine phosphatases SHP-1 and/or SHP-2. In the rat, SIRP is selectively expressed on myeloid cells (monocytes, macrophages, granulocytes, and dendritic cells) and neurons. The ligand for rat SIRP is CD47, which is similar to the interaction of the human homolog SIRPα1 (CD172α) and human CD47. The SIRP/CD47 interaction is thought to be important in maintaining cellular adhesion and possibly promote T-cell activation.
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.