The In-1 monoclonal antibody specifically binds to CD74, the MHC class II-associated Invariant chain (Ii), expressed in I-A+ cell populations. Although it is predominantly expressed intracellularly, it has also been detected on the cell surface of some B-cell lines and at low levels on a small number of B lymphocytes. In the mouse, alternatively spliced transcripts encode 31-kDa and 41-kDa isoforms, and the cell-surface CD74 has a chondroitin sulfate side chain which allows it to interact with CD44. CD74 is directly involved in the intracellular transport of MHC class II molecules and antigen presentation, and it affects the maturation of T and B lymphocytes.
The antibody was conjugated to BD Horizon™ BV711 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 711-nm. BD Horizon BV711 can be excited by the violet laser and detected in a filter used to detect Cy™5.5 / Alexa Fluor® 700-like dyes (eg, 712/20-nm filter). Due to the excitation and emission characteristics of the acceptor dye, there may be moderate spillover into the Alexa Fluor® 700 and PerCP-Cy5.5 detectors. However, the spillover can be corrected through compensation as with any other dye combination.