To the Editor: Interleukin 21 (IL-21) is a T-cell derived cytokine member of the common gamma-chain-dependent cytokine family, which in general acts on intestinal epithelium helping to maintain the ongoing Th1 inflammation inducing the production of IFN-c. 1 IL-21 also has shown to enhance the expansion of NK cells. IL-21 is expressed by immune T and B cells and nonimmune-like fibroblasts where it activates the metalloproteinase 1 production, signaling through its receptor IL-21R activates STAT-3 in T cells. IL-21, like IL-6 and IL-23, is also involved in Th17 cell differentiation and it is overexpressed in Crohn’s disease (CD). 2

Genetic variants in the region harboring IL2/IL21 have been associated with the genetic susceptibility for developing ulcerative colitis (UC). 3, 4 A recent study has reported IL-21 receptor (IL-21R)-positive cells were significantly increased in inflamed mucosa of inflammatory bowel disease (IBD) patients compared with controls, and mainly expressed in freshly isolated peripheral blood (PB) and lamina propria (LP)-CD4 (þ), CD8 (þ) T, B, and NK cells. 5 However, this is the first study to our best knowledge with a larger sample that explores the IL-21 gene expression from rectal biopsies in patients with UC.