The 3E7 monoclonal antibody specifically recognizes multifunctional C3b and iC3b fragments of the ~190 kDa plasma glycoprotein, Complement component 3 (C3). C3 is a key component of the classical, alternative and lectin complement activation pathways which participate in innate and adaptive immune responses to eliminate pathogens, dying cells, and immune complexes from the body. C3 is produced by hepatocytes, mast cells, and leucocytes including some monocytes, macrophages, dendritic cells (DC), and T cells. As a result of complement activation, eg, initiated by an antigen-antibody immune complex in the classical pathway, biologically active C3b fragments can be cleaved from C3 by enzymatic C3 convertases. C3b can function as an opsonin by binding covalently via its reactive thioester to the surfaces of target cells, including microbes. C3b can also bind to antigen-antibody immune complexes. Macrophages and neutrophils can recognize and bind to C3b by their complement receptors, such as Complement Receptor 1 (CR1, CD35), which enhances their phagocytosis of C3b-bound target cells or immune complexes. Opsonization of target surfaces, including the cell surfaces of pathogenic organisms, infected or tumor cells, through C3b deposition is central to all three pathways of complement activation during innate or adaptive immune responses. C3b can also associate with other components of the complement system to form a C5 convertase. This complex cleaves C5 into the C5a anaphylatoxin and C5b which initiates formation of the of the cytolytic membrane attack complex (MAC) that can produce holes in target cell membranes. C3b can be further cleaved into iC3b by factor I protease and its cofactors. The iC3b fragment serves as a ligand for engaging lymphoid and phagocytic cells via various receptors including CR2 (CD21), CR3 (CD11b/CD18), CR4 (CD11c/CD18), and CRIg. The 3E7 antibody van reportedly block the activation of the alternative pathway of complement.
This antibody is conjugated to BD Horizon™ BV605 which is part of the BD Horizon Brilliant™ Violet family of dyes. With an Ex Max of 407-nm and Em Max of 602-nm, BD Horizon BV605 can be excited by a violet laser and detected with a standard 610/20-nm filter set. BD Horizon BV605 is a tandem fluorochrome of BD Horizon BV421 and an acceptor dye with an Em max at 605-nm. Due to the excitation of the acceptor dye by the green (532 nm) and yellow-green (561 nm) lasers, there will be significant spillover into the PE and BD Horizon PE-CF594 detectors off the green or yellow-green lasers. BD Horizon BV605 conjugates are very bright, often exhibiting brightness equivalent to PE conjugates and can be used as a third color off of the violet laser.