Interleukin 21
Interleukin-21 also known as IL-21 is a protein that in humans is encoded by the IL21 gene.
Interleukin-21 is a cytokine that has potent regulatory effects on cells of the immune system, including natural killer (NK) cells and cytotoxic T cells that can destroy virally infected or cancerous cells. This cytokine induces cell division/proliferation in its target cells.
Gene
The human IL-21 gene is about 8.43kb, mapped to chromosome 4 and 180kb from IL-2 gene, and the mRNA product is 616 nucleotides long.
Tissue and cell distribution
IL-21 is expressed in activated human CD4+T cells but not in most other tissues. In addition, IL-21 expression is up-regulated in Th2 and Th17 subsets of T helper cells, as well as T follicular cells. Furthermore, IL-21 is expressed in NK T cells regulating the function of these cells.
Interleukin-21 is also produced by Hodgkin's lymphoma (HL) cancer cells (which is surprising because IL-21 was thought to be produced only in T cells). This observation may explain a great deal of the behavior of classical Hodgkin's lymphoma including clusters of other immune cells gathered around HL cells in cultures. Targeting IL-21 may be a potential treatment or possibly a test for HL.
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