Calcium signals are essential for diverse cellular functions in the immune system. Sustained Ca(2+) entry is necessary for complete and long-lasting activation of calcineurin/NFAT pathways. A growing number of studies have emphasized that Ca(2+)/Calcineurin/NFAT pathway is crucial for both development and function of regulatory T cells. (C) 2009 Elsevier Masson SAS. All rights reserved.