The OX-49 antibody reacts with the glycoprotein CD44H (also known as CD44s) expressed on most leukocytes, except for a subset of B lymphocytes, and at greatly increased levels on T- and B-cell blasts. The epitope recognized by OX-49 antibody has been mapped to a region on both the standard, CD44s, and the splice variant, CD44v, isoforms of CD44. However, recent reports indicate that OX-49 antibody cannot detect the CD44v isoform, possibly due to conformational changes in the epitope. CD44 is a cell adhesion receptor, and its ligand, hyaluronate, is a common component of extracellular matrices.
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.