Calcium signalling in T cells

Calcium (Ca 2+ ) signalling is of paramount importance to immunity. Regulated increases in cytosolic and organellar Ca 2+ concentrations in lymphocytes control complex and crucial effector functions such as metabolism, proliferation, differentiation, antibody and cytokine secretion and cytotoxicity. Altered Ca 2+ regulation in lymphocytes leads to various autoimmune, inflammatory and immunodeficiency syndromes. Several types of plasma membrane and organellar Ca 2+ -permeable channels are functional in T cells. They contribute highly localized spatial and temporal Ca 2+ microdomains that are required for achieving functional specificity. While the mechanistic details of these Ca 2+ microdomains are only beginning to emerge, it is evident that through crosstalk, synergy and feedback mechanisms, they fine-tune T cell signalling to match complex immune responses. In this article, we review the expression and function of various Ca 2+ -permeable channels in the plasma membrane, endoplasmic reticulum, mitochondria and endolysosomes of T cells and their role in shaping immunity and the pathogenesis of immune-mediated diseases.