| Synonyms | Za11, IL-21. |
| Introduction | IL-21 is produced by CD4+ T cells in response to antigenic stimulation. Its action enhances antigen-specific responses of immune cells. The biological effects of IL-21 include induction of differentiation of T-cells-stimulated B-cells into plasma cells and memory B-cells, stimulation （in conjuction） with IL-4 of IgG production, and induction of apoptotic effects in naive B-cells and stimulated B-cells in the absence of T-cell signaling. Additionally, IL-21 promotes the anti-tumor activity of CD8+ T-cells and NK cells. IL-21 exerts its effect through binding to a specific type I cytokine receptor, IL-21R, which also contains the gamma chain （°C） found in other cytokine receptors including IL-2, IL-4, IL-7, IL-9 and IL-15. The IL-21/IL-21R interaction triggers a cascade of events which includes activation of the tyrosine kinases JAK1 and JAK3, followed by activation of the transcription factors STAT1 and STAT3. |
| Description | Interleukin-21 Human Recombinant produced in E.Coli is a single, non-glycosylated polypeptide chain containing 133 amino acids and having a total molecular mass of 15,463 Dalton.
The IL-21 is purified by proprietary chromatographic techniques. |
| Source | Escherichia Coli. |
| Physical Appearance | Sterile Filtered White lyophilized （freeze-dried） powder. |
| Formulation | Lyophilized from a concentrated （1mg/ml） solution containing no additives. |
| Solubility | It is recommended to reconstitute the lyophilized Interleukin -21 in sterile 18MΩ-cm H2O not less than 100μg/ml, which can then be further diluted to other aqueous solutions. |
| Stability | Lyophilized Interleukin-21 although stable at room temperature for 3 weeks, should be stored desiccated below -18°C. Upon reconstitution IL21 should be stored at 4°C between 2-7 days and for future use below -18°C.
For long term storage it is recommended to add a carrier protein （0.1% HSA or BSA）.
Please prevent freeze-thaw cycles. |
| Purity | Greater than 95.0% as determined by:
（a） Analysis by RP-HPLC.
（b） Analysis by SDS-PAGE. |
| Amino acid sequence | The sequence of the first five N-terminal amino acids was determined and was found to be Gln-Gly-Gln-Asp-Arg. |
| Biological Activity | The ED50=1-10ng/ml, determined by the dose-dependant proliferation of human peripheral blood mononuclear cells. |
| Protein content | Protein quantitation was carried out by two independent methods:
1. UV spectroscopy at 280 nm using the absorbency value of 0.54 as the extinction coefficient for a 0.1% （1mg/ml） solution. This value is calculated by the PC GENE computer analysis program of protein sequences （InliGenetics）.
2. Analysis by RP-HPLC, using a standard solution of IL-21 as a Reference Standard. |
| Usage | ProSpec's products are furnished for LABORATORY RESEARCH USE ONLY. The product may not be used as drugs, agricultural or pesticidal products, food additives or household chemicals. |
