Calcium signalling in T cells.

Calcium (Ca) signalling is of paramount importance to immunity. Regulated increases in cytosolic and organellar Ca concentrations in lymphocytes control complex and crucial effector functions such as metabolism, proliferation, differentiation, antibody and cytokine secretion and cytotoxicity. Altered Ca regulation in lymphocytes leads to various autoimmune, inflammatory and immunodeficiency syndromes. Several types of plasma membrane and organellar Ca-permeable channels are functional in T cells. They contribute highly localized spatial and temporal Ca microdomains that are required for achieving functional specificity. While the mechanistic details of these Ca 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-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.