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 an oligonucleotide that contains an antibody clone-specific barcode (ABC) flanked by a poly-A tail on the 3' end and a PCR handle (PCR primer binding site) on the 5' end. The ABC for this antibody was designed to be used with other BD AbSeq oligonucleotides conjugated to other antibodies. All AbSeq ABC sequences were selected in silico to be unique from human and mouse genomes, have low predicted secondary structure, and have high Hamming distance within the BD AbSeq portfolio, to allow for sequencing error correction and unique mapping. The poly-A tail of the oligonucleotide allows the ABC to be captured by the BD Rhapsody™ system or other oligo-dT-based capture systems. The 5' PCR handle allows for efficient sequencing library generation for Illumina sequencing platforms.