The HP-MA4 monoclonal antibody specifically recognizes several Killer Cell Immunoglobulin-like Receptors (KIRs) which are also known as CD158 molecules. HP-MA4 recognizes Killer cell immunoglobulin-like receptor 2DL1 (encoded by KIR2DL1; aka, CD158a and NKAT-1), Killer cell immunoglobulin-like receptor 2DS1 (KIR2DS1; CD158h), Killer cell immunoglobulin-like receptor 2DS3 (KIR2DS3; NKAT-7), and Killer cell immunoglobulin-like receptor 2DS5 (KIR2DS5; CD158g, NKAT-9) which are collectively known as KIR2DL1/S1/S3/S5 (CD158). These type I transmembrane glycoproteins are encoded by polymorphic genes and have 2 extracellular Ig-like domains (KIR2D, domains D1 and D2) followed by a transmembrane region and either long (L) or short (S) cytoplasmic domains. Various CD158 molecules are differentially expressed by CD56dim natural killer (NK) cells and some T cells and can regulate their cytotoxic effector functions. Although different KIR gene content varies amongst haplotypes for individuals, certain "framework" genes including KIR3DL3, KIR3DP1, KIR3DL4, and KIR3DL2, are found in all haplotypes. KIR2DL1 has a long cytoplasmic domain with two tyrosine-based inhibitory motifs (ITIM) that enables inhibitory signal transduction by ligand-bound KIR2DL1 leading to reduced cytotoxic effector cell activity. KIR2DS1, KIR2DS3, KIR2DS5 (KIR2DS1/S3/S5) proteins each have a short cytoplasmic tail with a positively charged amino acid in their transmembrane region which allows association with the DAP12 transmembrane protein. DAP12 acts as an activating signal transduction element through its immunoreceptor tyrosine-based activation motifs (ITAMs) in its cytoplasmic domain leading to upregulated cytotoxic effector cell function. Some MHC class I molecules can serve as ligands for CD158 molecules, with HLA-C ligands reported for KIR2DL1, KIR2DS1, and KIR2DS5.
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.