The 17A12 monoclonal antibody specifically binds to the IL-21 Receptor (IL-21R). The IL-21R, also known as CD360, is a 538 amino acid cytokine receptor with an extracellular domain consisting of one copy of the conserved WSXWS -containing cytokine-binding domain. The IL-21 receptor combines with the common cytokine-receptor γ-chain to form a functional receptor complex for IL-21. IL-21 is mainly produced by activated CD4+ T cells including T follicular helper (Tfh) cells. IL-21R is preferentially expressed by B cells, T cells, NK cells, some populations of myeloid cells, keratinocytes, and dendritic cells. Binding of its ligand, IL-21, in these cells results in the activation of the Jak/Stat signal transduction pathway. The effects IL-21 ligand binding has pleiotropic actions such as augmenting the proliferation of T cells, driving of B cells into memory cells, terminally differentiating plasma cells and augmenting the activity of natural killer cells. IL-21 receptor has anti-tumor activity and might have a role in the development of autoimmunity; it has been reported that the IL-21 receptor affects the homeostasis of regulatory T cells and it could enhance T cell-activated responses in human immune-inflammatory diseases.
The antibody was conjugated to BD Horizon™ BV786 which is part of the BD Horizon Brilliant™ Violet family of dyes. This dye is a tandem fluorochrome of BD Horizon BV421 with an Ex Max of 405-nm and an acceptor dye with an Em Max at 786-nm. BD Horizon BV786 can be excited by the violet laser and detected in a filter used to detect Cy™7-like dyes (eg, 780/60-nm filter).