The MRα4-1 antibody reacts with the integrin α4 chain, which is expressed as a heterodimer with either of two β chains, β1 or β7. The α4β1 integrin (VLA-4, CD49d/CD29) is expressed on peripheral T and B lymphocytes, thymocytes, and monocytes; while the α4β7 integrin (LPAM-1) is expressed on peripheral lymphocytes. These integrins mediate a variety of cell-cell and cell-matrix interactions, recognizing the ligands CD106 (VCAM-1), MAdCAM-1, and fibronectin. It has been reported that soluble mAb MRα4-1 partially inhibits in vitro binding of VCAM-1 and mast cells to fibronectin and inhibits the enhanced degranulation of IgE-sensitized RBL-2H3 basophilic leukemia cell line induced on fibronectin-coated plates. Furthermore, plate-bound MRα4-1 antibody enhances the degranulation of IgE-sensitized RBL-2H3 cells; and subcutaneous injection of MRα4-1 mAb, along with anti-CD49e and anti-CD61 antibodies, inhibits experimentally induced passive cutaneous anaphylaxis.
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.