The 4G8 monoclonal antibody specifically binds to CD135 which is also known as FMS-like tyrosine kinase 3 (FLT3), Fetal liver kinase 2 (FLK2) and Stem cell tyrosine kinase 1 (STK1). CD135 is a 155-160 kDa type I transmembrane glycoprotein. It belongs to subclass III of the receptor tyrosine kinase (RTK) family which includes receptors for M-CSF (CD115), SCF/c-Kit Ligand (CD117), and PDGF (CD140a and CD140b). CD135 is expressed on multipotential, myelomonocytic and primitive B-cell progenitors. The most primitive hematopoietic progenitor cells express low levels of CD135. CD135 plays the role of growth factor receptor for early hematopoietic progenitors. Reports from studies with knockout mice have shown that targeted CD135 disruption impaired the development of primitive progenitor cells of all hematopoietic lineages with significant impact on lymphopoietic precursors.
The antibody was conjugated to BD Horizon™ BUV737 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 737-nm. BD Horizon Brilliant BUV737 can be excited by the ultraviolet laser (355 nm) and detected with a 740/35 filter. Due to the excitation of the acceptor dye by other laser lines, there may be significant spillover into channels detecting Alexa Fluor® 700-like dyes (eg, 712/20-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 BUV737 reagents. Therefore, the use of BD CompBeads or BD CompBeads Plus to determine spillover values for these reagents is not recommended. Different BUV737 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.