The 493 antibody reacts with a cell-surface protein of 130-140 kDa expressed on immature B lymphocytes and a small fraction of newly formed B cells, but not on mature B lymphocytes. The antigen's distribution was defined through the use of antibodies to CD24 (Heat Stable Antigen), IgM, IgD, and CD45R/B220, which are commonly used to discriminate B-cell maturation stages. 493 mAb reacts with the majority of B220+ cells in bone marrow and a fraction of B220+ B cells in spleen, which are CD24[high], IgM[high], and IgD[low]. Cells binding 493 mAb were not detected in thymus, lymph nodes, or peritoneal cavity. This result suggested that 493 mAb does not stain B-1 B cells (CD5+ B lymphocytes), which are particularly found in the peritoneal cavity. The 493 mAb does not seem to have any biological effect when incubated with immature B lymphocytes. It has been observed that the staining pattern of mAb 493 is similar to that of mAb AA4.1, that both antibodies precipitate molecules of the same molecular weight, and that staining by mAb AA4.1 is not blocked by mAb 493, suggesting that the antibodies recognize separate epitopes of the same Early B Lineage antigen.
This antibody is conjugated to BD Horizon™ BV605 which is part of the BD Horizon Brilliant™ Violet family of dyes. With an Ex Max of 407-nm and Em Max of 602-nm, BD Horizon BV605 can be excited by a violet laser and detected with a standard 610/20-nm filter set. BD Horizon BV605 is a tandem fluorochrome of BD Horizon BV421 and an acceptor dye with an Em max at 605-nm. Due to the excitation of the acceptor dye by the green (532 nm) and yellow-green (561 nm) lasers, there will be significant spillover into the PE and BD Horizon PE-CF594 detectors off the green or yellow-green lasers. BD Horizon BV605 conjugates are very bright, often exhibiting brightness equivalent to PE conjugates and can be used as a third color off of the violet laser.