The 22-19-12 monoclonal antibody specifically recognizes CXC chemokine ligand 16 (CXCL16) which is also known as C-X-C motif chemokine 16, Scavenger receptor for phosphatidylserine and oxidized low density lipoprotein (SR-PSOX), or Small-inducible cytokine B16 (SCYB16). CXCL16 is a ~30 kDa single-pass type I transmembrane glycoprotein with an extracellular CXC chemokine domain and mucin-like spacer region, followed by a transmembrane region, and a cytoplasmic domain with consensus tyrosine phosphorylation and SH2 binding sites. Transmembrane CXCL16 can serve as a scavenger receptor that binds to oxidized low density lipoprotein, phosphatidylserine, or bacteria and mediates their uptake by macrophages and dendritic cells. Cell surface CXCL16 can be shed in a soluble form after proteolytic cleavage to exert its chemotactic function. CXCL16 is differentially expressed by keratinocytes, monocytes, dendritic cells, endothelial cells, and some activated T cells. CXCL16 exerts its chemotactic function by binding to and signaling through the CXCR6 (CD186) chemokine receptor that is variably expressed by effector/memory CD8+ T cells, CD4+ T cells with Th1- or Th17-like phenotypes, γδ T cells, natural killer (NK) cells, natural killer T (NKT) cells, and monocytes. The 22-19-12 antibody reportedly binds to the chemokine domain of CXCL16 and can inhibit the chemotactic activity of soluble CXCL16.
The antibody was conjugated to BD Horizon™ BV650 which is part of the BD Horizon Brilliant™ Violet family of dyes. This dye is a tandem fluorochrome of BD Horizon BV421 with an Ex Max of 405-nm and an acceptor dye with an Em Max at 650-nm. BD Horizon BV650 can be excited by the violet laser and detected in a filter used to detect APC-like dyes (eg, 660/20-nm filter). Due to the excitation and emission characteristics of the acceptor dye, there will be spillover into the APC and Alexa Fluor® 700 detectors. However, the spillover can be corrected through compensation as with any other dye combination.