About CD19
This gene encodes a member of the immunoglobulin gene superfamily. Expression of this cell surface protein is restricted to B cell lymphocytes. This protein is a reliable marker for pre-B cells but its expression diminishes during terminal B cell differentiation in antibody secreting plasma cells. The protein has two N-terminal extracellular Ig-like domains separated by a non-Ig-like domain, a hydrophobic transmembrane domain, and a large C-terminal cytoplasmic domain. This protein forms a complex with several membrane proteins including complement receptor type 2 (CD21) and tetraspanin (CD81) and this complex reduces the threshold for antigen-initiated B cell activation. Activation of this B-cell antigen receptor complex activates the phosphatidylinositol 3-kinase signalling pathway and the subsequent release of intracellular stores of calcium ions. This protein is a target of chimeric antigen receptor (CAR) T-cells used in the treatment of lymphoblastic leukemia. Mutations in this gene are associated with the disease common variable immunodeficiency 3 (CVID3) which results in a failure of B-cell differentiation and impaired secretion of immunoglobulins. CVID3 is characterized by hypogammaglobulinemia, an inability to mount an antibody response to antigen, and recurrent bacterial infections. Alternative splicing results in multiple transcript variants encoding distinct isoforms. [provided by RefSeq, Jul 2020]

About Brilliant Violet 421
Brilliant™ Violet 421 (BV421) is a Violet-emitting non-tandem polymer fluorophore that can be excited by the 405 nm Violet laser and collected using a 450/50 bandpass filter. BV421 has an excitation peak at 405 nm and an emission peak at 421 nm, and is spectrally similar to Alexa Fluor™ 405 and Cascade Blue. Other dyes that are considered similar include SuperNova V428 (Beckman Coulter), StarBright Violet 440 (Bio-Rad) and SuperBright 436 (Thermo Fisher). BV421 is very bright and is most commonly used for flow cytometry. Its photostablity, fixation stablity, and non-toxicity properties also make BV421 useful for cell sorting and live cell Fluorescence Microscopy applications. This dye is part of the Brilliant™ Violet dye line of fluorescent polymers. Brilliant™ Violet 421 polymer is employed as the donor molecule in a series of tandem dyes with acceptor molecules emitting at various points across the visible light spectrum. The Brilliant™ Violet dyes are a superior alternative to QDot nanocrystals and similar to SuperNova dye from Beckman Coulter and StarBright dyes from Bio-Rad.