This product is a FCM antibody cocktail made up of FITC Anti-Human CD3 Antibody [Clone: OKT-3] (Mouse IgG2a, κ), APC Anti-Human CD19 Antibody [Clone: CB19] (Mouse IgG1, κ), PE Anti-Human CD16 Antibody [Clone: 3G8] (Mouse IgG1, κ) and PE Anti-Human CD56 Antibody [Clone: 5.1H11] (Mouse IgG1, κ).; CD3 is a heterotetrameric protein consisting of a CD3γ, a CDδ and 2 CD3ε. It forms complex with TCR. OKT-3 recognize human CD3ε. Human CD3 is expressed on the surface of T cells and NKT cells.; CD19 is a single-chain transmembrane glycoprotein expressed on B cells of all stages except plasma cells. It is a common marker for B cells. CD19 is also expressed in follicular dendritic cells. It forms complex with CD21 and CD84, which forms co-receptor with BCR. It takes part in B cell development, activantion and differentiation.; CD16 is a low affinity receptor for the Fc of IgG. Human CD16 has two isoforms, CD16a and CD16b. CD16a is expressed on NK cells, activated monocytes and macrophages. CD16b is expressed on neutrophils. NK cells exert the function of ADCC by binding Fc of IgG through CD16.; CD56 is also call neural cell adhesion molecule (NCAM), expressed on neurons, glia and skeletal muscle cells. In hematopoietic cells, CD56 is also expressed on NK cells and NKT cells. CD56 can be used to detect NK cells, γ/δ T cells and activated CD8+ cells.