The UCH-B1 (also known as, UCHB1) monoclonal antibody specifically recognizes the heavy chain constant region (Cµ) of human Immunoglobulin M (IgM) that is encoded by IGHM (immunoglobulin heavy constant mu). It does not crossreact with other immunoglobulin heavy or light chain isotypes. An intracytoplasmic form of IgM is expressed by pre-B cells whereas immature and a portion of mature B cells, including naive and memory B cells, express cell surface IgM. These forms of IgM can also be expressed by cells from some leukemias or lymphomas. Cell surface IgM is comprised of two type I transmembrane heavy chain glycoproteins (Igµ heavy chains) that are paired with immunoglobulin light chains of the same type, ie, either immunoglobulin kappa (Igκ) or lambda (Igλ) light chains. Cell surface IgM serves as a receptor that can specifically bind to antigens, including those expressed by microbial pathogens, and trigger the clonal expansion and differentiations of B cells into antibody-secreting plasma cells. A soluble pentameric form of IgM can be produced and secreted by plasma cells into the blood. Pentameric IgM is comprised of 5 monomers that consist of two Igµ heavy chains and two light chains that are complexed with a polypeptide J-chain. The UCH-B1 monoclonal antibody recognizes both cell surface and soluble human IgM. IgM is an important component in the first line of defense against foreign pathogens, but may also play a role in autoimmune diseases. The UCH-B1 antibody can reportedly activate or costimulate the proliferation of normal B cells or some transformed B cell lines.
The antibody was conjugated to BD Horizon BUV496 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 496-nm. BD Horizon BUV496 can be excited by the ultraviolet laser (355 nm) and detected with a 515/30 nm filter with a 450LP. Due to the excitation of the acceptor dye by other laser lines, there may be significant spillover into the channel detecting BD Horizon V500 or BV510 (eg, 525/40-nm filter). However, the spillover can be corrected through compensation as with any other dye combination.