The RPM.4 monoclonal antibody specifically recognizes CD42d (Platelet glycoprotein V, GPV). CD42d is a 88-kDa type I transmembrane glycoprotein which noncovalently associates with GPIb and GPIX to form a receptor for von Willebrand factor on megakaryocytes and resting platelets. The binding sites for von Willebrand factor and thrombin have been localized to the GPIbα chain of the GPI-b-V-IX complex. GPV is cleaved by thrombin to release a 70 kDa soluble fragment, which contains the epitope recognized by mAb RPM.4. Although the rat CD42d protein's structure is similar to that of human CD42d, the RPM.4 antibody does not cross-react with human platelets.
The antibody was conjugated to BD Horizon™ BUV496 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 496-nm. BD Horizon BUV496 can be excited by the ultraviolet laser (355 nm) and detected with a 515/30 nm filter with a 450LP. Due to the excitation of the acceptor dye by other laser lines, there may be significant spillover into the channel detecting BD Horizon V500 or BV510 (eg, 525/40-nm filter). However, the spillover can be corrected through compensation as with any other dye combination.