The 3D3 monoclonal antibody specifically recognizes FcγRII (CD32), a 40 kDa, polymorphic type I transmembrane glycoprotein that serves as a low affinity receptor for aggregated IgG. This highly glycosylated molecule (encoded by at least two different genes) is expressed on monocytes, granulocytes, platelets and B cells. Unlike the FLI28.26 mAb, the 3D3 mAb detected a polymorphic CD32 antigen expressed on B cells of all donors, but only on platelets, monocytes and granulocytes of some donors. The platelets from 3D3+ donors respond to certain stimulatory mAb such as CD165 (clone SN2) which results in aggregation. On the other hand, the platelets from 3D3 negative donors do not form aggregates after stimulation. Individuals can be divided into two groups as responder and non-responder depending on expression, or non-expression, of 3D3. In comparison to the 3D3 mAb, the FLI8.26 mAb detects a monomorphic CD32 antigen expressed on all human donors.
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.