IL-21 is produced by CD4+ T cells in response to antigenic stimulation, which enhances antigen-specific responses of immune cells. IL-21 exerts its effect through binding to a specific type I cytokine receptor, IL-21R, which also contains the gamma chain 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.

Expression System
Escherichia coli

Sequence
MQDRHMIRMRQLIDIVDQLKNYVNDLVPEFLPAPEDVETNCEWSAFSCFQKAQLKSANTGNNERIINVSIKKLKRKPPSTNAGRRQKHRLTCPSCDSYEKKPPKEFLERFKSLLQKMIHQHLSSRTHGSEDS with polyhistidine tag at the C-terminus.

Species
Human

Tag
polyhistidine tag at the C-terminus

Endotoxin Level
<0.1 EU per 1 μg of the protein by the LAL method.

Activity
Measure by its ability to enhance IFN gamma secretion in NK-92 cells. The ED₅₀ for this effect is <10 ng/mL.

Purity
>95% as determined by SDS-PAGE. Ni-NTA chromatography

Formulation
The protein was lyophilized from a solution containing 1X PBS, pH 8.0.

Reconstitution
It is recommended to reconstitute the lyophilized protein in sterile H₂O to a concentration not less than 100 μg/mL and incubate the stock solution for at least 20 minutes to ensure sufficient re-dissolved.

SDS-PAGE analysis of recombinant human IL-21