The BC4 antibody reacts with the high-affinity IgE Fc receptor (FcεRI) expressed in rat mast cells, basophils, and non-B non-T cells. The rat FcεRI is expressed as a tetrameric molecule consisting of one α chain, one β chain, and two identical γ chains. The BC4 antibody has been reported to detect all three chains of the FcεRI by immunoprecipitation. In the rat model, the β chain (FcRβ) is required for cell-surface expression of the complete FcεRI. This differs from the human FcεRI, which can be expressed in trimer (αγ2) or tetramer forms (βγ2). Furthermore, the FcRβ has been characterized as a potent signaling molecule capable of substantially amplifying Fc-mediated cellular responses. The FcεRI functions to mediate cellular degranulation and the release of histamine, leukotrienes, and various cytokines and chemokines. The structure, expression, function, and signaling mechanisms of the FcεRI have been reviewed.
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.