The 159227 monoclonal antibody specifically recognizes MHC class I polypeptide-related sequence A (MICA) which is also known as MIC-A, MHC class I chain-related protein A, or stress inducible class I homolog. This ~70 kDa single-pass type I transmembrane glycoprotein is encoded by MICA (major histocompatibility complex class I chain-related gene A) which is a highly polymorphic gene. MICA is very homologous to another protein, MICB. Both MICA and MICB are homologous to major histocompatibility complex (MHC) class I molecules although they lack association with β2 microglobulin. MICA and MICB each contain three extracellular Ig domains but have no capacity to bind peptides. MICA is expressed on some gut epithelial cells. Its expression by other epithelial cells and cell types, including fibroblasts and endothelial cells, is induced by stress, eg, stress caused by bacterial and viral infections, autoimmunity, transplantation rejection, or cellular transformation. MICA and MICB are ligands for NKG2D (CD314), an activating receptor expressed by natural killer (NK) cells, γδ T cells, CD8+ αβ T cells, and some CD4+ αβ T cells.
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).
Due to spectral differences between labeled cells and beads, using BD™ CompBeads can result in incorrect spillover values when used with BD Horizon BUV661 reagents. Therefore, the use of BD CompBeads or BD CompBeads Plus to determine spillover values for these reagents is not recommended. Different BUV661 reagents (eg, CD4 vs. CD45) can have slightly different fluorescence spillover therefore, it may also be necessary to use clone-specific compensation controls when using these reagents.