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™ BUV563 which is part of the BD Horizon Brilliant™ Ultraviolet family of dyes. This dye is a tandem fluorochrome of BD Horizon BUV395 which has an Ex Max of 348 nm and an acceptor dye. The tandem has an Em Max at 563 nm. BD Horizon BUV563 can be excited by the 355 nm ultraviolet laser. On instruments with a 561 nm Yellow-Green laser, the recommended bandpass filter is 585/15 nm with a 535 nm long pass to minimize laser light leakage. When BD Horizon BUV563 is used with an instrument that does not have a 561 nm laser, a 560/40 nm filter with a 535 nm long pass may be more optimal. Due to the excitation and emission characteristics of the acceptor dye, there may be spillover into the PE and PE-CF594 detectors. However, the spillover can be corrected through compensation as with any other dye combination.