The ZM3.8 monoclonal antibody specifically binds to CD85k which is also known as Immunoglobulin-like transcript 3 (ILT-3) and Monocyte inhibitory receptor HM18. CD85k is encoded by LILRB4 (Leukocyte immunoglobulin-like receptor, subfamily B member 4) and is expressed as a type I transmembrane glycoprotein. CD85k is comprised of two C2-type Ig domains, a transmembrane region, and a cytoplasmic tail with three immunoreceptor tyrosine-based inhibitory motifs (ITIMs). CD85k is selectively expressed by myeloid antigen presenting cells including monocytes, macrophages, and dendritic cells. CD85k functions as an inhibitory receptor. ILT3 can also function in antigen capture and presentation. It is efficiently internalized upon cross-linking, and delivers its ligand to an intracellular compartment where it is processed and ultimately presented by APCs to T cells. Thus, ILT3 is a novel inhibitory receptor that can negatively regulate activation of APCs and can be used by APCs for antigen uptake. ILT3 expression is upregulated on tolerogenic dendritic cells that can induce regulatory T cells.
The antibody was conjugated to BD Horizon BUV615 which is part of the BD Horizon Brilliant™ Ultraviolet family of dyes. This dye is a tandem fluorochrome with an Ex Max near 350 nm and an Em Max near 615 nm. BD Horizon Brilliant BUV615 can be excited by the ultraviolet laser (355 nm) and detected with a 610/20 filter and a 595 nm LP. Due to the excitation of the acceptor dye by the blue/yellow-green laser line, there may be significant spillover into channels detecting PE-CF594 like emissions (eg, 610/20-nm filter).