| Background | 
                                Interleukin-21 (IL-21) belongs to the IL-15/IL-21 family, which exerts pleiotropic immune regulations. IL-21 produced primarily by natural killer T (NKT) cells, T follicular helper (TFH) cells and TH17 cells. As a pleiotropic cytokine, IL-21 has been shown to regulate both innate and humoral immunity. It has potent inhibitory activity towards the activation and maturation of granulocyte-macrophage colony-stimulating factor (GM-CSF)-induced dendritic cells (DCs). In B cells, IL-21 has a major role in the development of immunoglobulin responses. In T cells, it is required to facilitate the functional differentiation of several CD4+ T cell subsets. In addition, the ability of IL-21 to enhance the cytotoxic activity of both CD8+ T cells and NK cells makes it as a potential antitumor agent. | 
                            
                            
                            
                                | Synonyms | 
                                interleukin 21, Za11, IL21 | 
                            
                            
                            
                                | Uniprot ID | 
                                Q9HBE4 | 
                            
                            
                            
                                | Molecular Weight | 
                                The protein has a calculated MW of 16.2 kDa.
The protein migrates as 20 kDa under reducing condition (SDS-PAGE analysis). | 
                            
                            
                            
                                | Expression System | 
                                Escherichia coli | 
                            
                            
                            
                                | Purity | 
                                >95% as determined by SDS-PAGE analysis. | 
                            
                            
                            
                                | Activity | 
                                Measure by its ability to enhance IFN gamma secretion in NK-92 cells. The ED₅₀ for this effect is <10 ng/mL. | 
                            
                            
                            
                                | Endotoxin Level | 
                                <0.05 EU per 1 μg of the protein by the LAL method. | 
                            
                            
                            
                                | Protein Sequence | 
                                MQDRHMIRMRQLIDIVDQLKNYVNDLVPEFLPAPEDVETNCEWSAFSCFQKAQLKSANTGNNERIINVSIKKLKRKPPSTNAGRRQKHRLTCPSCDSYEKKPPKEFLERFKSLLQKMIHQHLSSRTHGSEDS with polyhistidine tag at the C-terminus. | 
                            
                            
                            
                                | Protein Tag | 
                                His Tag (C-term) | 
                            
                            
                            
                                | Form | 
                                Lyophilized from a 0.2 µm filtered solution of PBS, pH 8.0. | 
                            
                            
                           
                              
                                | Application | 
                                Cell Culture |