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 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).