The BRIC 203 monoclonal antibody specifically binds to the Kell blood group antigen, Kp(a-b+) but not Kp(a+b-), also known as the Kell blood group metallo-endopeptidase, KELL, ECE3 and CD238. CD238 is an approximately 115-kDa type II transmembrane glycoprotein that is encoded by the KEL gene. CD238 functions as a zinc endopeptidase that cleaves endothelin-3 into an active form which can function as a vasoconstrictor. CD238 is expressed on erythrocytes, human embryonic stem cell-derived endoderm and on cells from various other tissues, including testis, heart, brain and skeletal muscle. Decreased expression of CD238 is associated with the McLeod phenotype as a consequence of losing XK protein expression. Kell antigen expression can play an important role during blood transfusions and also specific autoimmune diseases related to Kell antigen recognition. During development the BRIC 203 monoclonal antibody was found to detect the CD238 antigen by flow cytometric analysis of human erythrocytes. It reportedly works in immunoprecipitation and agglutination assays.
The antibody was conjugated to BD Horizon™ BUV661 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 661-nm. BD Horizon Brilliant BUV661 can be excited by the ultraviolet laser (355 nm) and detected with a 670/25 filter and a 630 nm LP. Due to cross laser excitation of this dye, there may be significant spillover into channels detecting APC-like emissions (eg, 670/25-nm filter).
Due to spectral differences between labeled cells and beads, using BD™ CompBeads can result in incorrect spillover values when used with BD Horizon BUV661 reagents. Therefore, the use of BD CompBeads or BD CompBeads Plus to determine spillover values for these reagents is not recommended. Different BUV661 reagents (eg, CD4 vs. CD45) can have slightly different fluorescence spillover therefore, it may also be necessary to use clone-specific compensation controls when using these reagents.