Interleukin-21 (IL-21)-mediated pathways in T cell-mediated disease

Interleukin-21 (IL-21) is produced mostly by activated CD4+ T cells and controls the differentiation and functional activity of effector T helper cells, counteracts the suppressive effects of regulatory T cells, and stimulates non-immune cells to make inflammatory mediators. IL-21-driven tissue damage has been demonstrated in a number of organs, such as the gut, pancreas, and brain. Therefore new treatment modalities to neutralise IL-21 in vivo would be a valuable addition to the therapeutic armamentarium to combat immune-mediated inflammation. Here we describe the emerging role of IL-21 in the initiation and progress of the tissue-damaging inflammatory response in immune-mediated pathologies. (C) 2009 Elsevier Ltd. All rights reserved.