The HM79b monoclonal antibody specifically recognizes an extracellular epitope of Ig β chain (Igβ or CD79b), a 35-40-kDa transmembrane protein which forms an 80-90-kDa disulfide-linked heterodimer with Ig α chain (Igα or CD79a, 30-35 kDa). On mature B lymphocytes, the CD79a/CD79b heterodimers are non-covalently associated with surface IgM to form the B-cell receptor complex (BCR). The presence of CD79a/CD79b is necessary for surface expression of the BCR and signal transduction via the BCR in B lymphocytes and pre-B cells. It was recently reported that CD79b may be expressed on the cell surface preceding the appearance of surface IgM during B-lymphocyte development. At this pro-B-cell stage, CD79b participates in signal transduction involved in the regulation of B-cell development. It should be noted that multi-parameter flow cytometric analyses of bone marrow suspensions performed at BD Biosciences Pharmingen have been unable to detect surface staining by HM79b mAb on CD45R/B220+ IgM- cells.
The antibody was conjugated to BD Horizon BUV615 which is part of the BD Horizon Brilliant™ Ultraviolet family of dyes. This dye is a tandem fluorochrome with an Ex Max near 350 nm and an Em Max near 615 nm. BD Horizon Brilliant BUV615 can be excited by the ultraviolet laser (355 nm) and detected with a 610/20 filter and a 595 nm LP. Due to the excitation of the acceptor dye by the blue/yellow-green laser line, there may be significant spillover into channels detecting PE-CF594 like emissions (eg, 610/20-nm filter).