Technical Articles

Interleukin-21 (IL-21) is a pleiotropic cytokine produced by activated T cells, serving as a central messenger in coordinating humoral immunity, cellular immunity, and immune tolerance. It plays a complex and critical role in promoting antibody production, cytotoxic cell activation, and immune regulation.

B-cell polarizing cytokines are a group of key signaling molecules that direct B-cell differentiation, antibody class switching, and functional specialization.

IL-21 is a four alpha helix cytokine composed of 133 amino acids, belonging to the gamma chain cytokine family (gamma c family). The family members include IL-2, IL-4, IL-7, IL-9, IL-15, and IL-21, all of which utilize a common gamma chain (γ c, CD132) as a receptor signaling subunit. Structurally, IL-21 contains four conserved alpha helical domains (A, B, C, D) that bind to receptors through specific spatial conformations.