Calcium (Ca2+) plays a major role in life and death in T-Cells. Elevation of intracellular free Ca2+ is one of the key triggering signals for T-Cell activation by antigen. The binding of antigen-MHC Class-II complex on antigen presenting cells (APC) to the TCR-CD3 complex on T-cells triggers the recruitment of several tyrosine kinases and substrates to the TCR/CD3/CD4 complex, ultimately resulting in the phosphorylation and activation of PLC-γ1. PLC-γ1 cleaves PIP2 in the plasma membrane to generate DAG and IP3, which activate PKC and cause accumulation of free Ca2+ in the cytosol respectively. Intracellular free Ca2+ can come from two sources: the endoplasmic reticulum and the extracellular space...