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™ BV711 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 711-nm. BD Horizon BV711 can be excited by the violet laser and detected in a filter used to detect Cy™5.5 / Alexa Fluor® 700-like dyes (eg, 712/20-nm filter). Due to the excitation and emission characteristics of the acceptor dye, there may be moderate spillover into the Alexa Fluor® 700 and PerCP-Cy5.5 detectors. However, the spillover can be corrected through compensation as with any other dye combination.