The MD22 monoclonal antibody specifically recognizes CD64 which is also known as Fc-gamma receptor I (FcgR1) or FcγRI. CD64 is a ~72 kDa type I transmembrane glycoprotein that is encoded by FCGR1A (Fc fragment of IgG receptor Ia). CD64 functions as a high affinity receptor for human IgG. The CD64 antigen is expressed on monocytes, macrophages, at low levels on polymorphonuclear neutrophils (PMNs), and on a subpopulation of circulating dendritic cells. The CD64 antigen is an early granulomonocytic lineage marker on CD34+ hematopoietic progenitors. Expression of the CD64 antigen increases transiently in cases of sepsis. The CD64 antigen functions in both innate and adaptive immune responses, and mediates endocytosis, phagocytosis, antigen presentation, antibody-dependent cellular cytotoxicity, cytokine release, and superoxide generation. The CD64 antigen associates with the signal-transducing γ-chain homodimer of Fc receptors to form the functional high affinity FcγRI complex. Ligation of the CD64 antigen leads to the activation of the protein tyrosine kinases, hck and lyn.
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).