Hu Recom IL-21, 50 µg

A pleiotropic cytokine composed of four α-helical bundles, this recombinant human protein is primarily produced by natural killer T (NKT) cells, T follicular helper (Tfh) cells, and Th17 cells. It signals through heterodimers of the IL-21 receptor (IL-21R) and the IL2RG-encoded common cytokine receptor γ-chain, activating the JAK/STAT, MAPK, and PI3K pathways. The cytokine plays a critical role in regulating immunoglobulin production and the differentiation of pro-inflammatory Th17 cells, sustains CD8+ T cell effector activity, and supports CD4+ T cell help during chronic viral infection.

Supplied by STEMCELL Technologies, the protein is produced in E. coli and provided as a lyophilized powder dialyzed against phosphate-buffered saline. Purity is ≥ 95% and endotoxin level is ≤ 0.2 EU/μg protein. The predicted molecular mass is 15.4 kDa (UniProt accession Q9HBE4), with cross-reactivity reported for mouse. Biological activity is determined by the ability to inhibit the proliferation of Mino cells; specific activity is ≥ 2 x 10^6 units/mg, with an EC50 of ≤ 0.5 ng/mL. For use, the product should be reconstituted in sterile water to at least 0.1 mg/mL without vortexing, and stored at -80°C, where it remains stable as supplied for 12 months from the date of receipt.